Merge remote-tracking branch 'upstream/master' into zvision

Conflicts:
	engines/zvision/animation/rlf_animation.cpp
	engines/zvision/animation_control.h
	engines/zvision/core/console.cpp
	engines/zvision/core/events.cpp
	engines/zvision/cursors/cursor.cpp
	engines/zvision/cursors/cursor_manager.cpp
	engines/zvision/cursors/cursor_manager.h
	engines/zvision/fonts/truetype_font.cpp
	engines/zvision/graphics/render_manager.cpp
	engines/zvision/graphics/render_manager.h
	engines/zvision/inventory/inventory_manager.h
	engines/zvision/inventory_manager.h
	engines/zvision/meta_animation.h
	engines/zvision/module.mk
	engines/zvision/scripting/actions.cpp
	engines/zvision/scripting/control.h
	engines/zvision/scripting/controls/animation_control.cpp
	engines/zvision/scripting/controls/animation_control.h
	engines/zvision/scripting/controls/input_control.cpp
	engines/zvision/scripting/controls/lever_control.cpp
	engines/zvision/scripting/controls/timer_node.cpp
	engines/zvision/scripting/controls/timer_node.h
	engines/zvision/scripting/puzzle.h
	engines/zvision/scripting/scr_file_handling.cpp
	engines/zvision/scripting/script_manager.cpp
	engines/zvision/scripting/script_manager.h
	engines/zvision/sidefx.cpp
	engines/zvision/sound/zork_raw.cpp
	engines/zvision/sound/zork_raw.h
	engines/zvision/video/video.cpp
	engines/zvision/video/zork_avi_decoder.h
	engines/zvision/zvision.cpp
	engines/zvision/zvision.h

11 files changed, 1872 insertions, 1614 deletions

diff --git a/backends/graphics/opengl/debug.cpp b/backends/graphics/opengl/debug.cpp
new file mode 100644
index 0000000000..d5d73fb5ec
--- /dev/null
+++ b/backends/graphics/opengl/debug.cpp
@@ -0,0 +1,65 @@
+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+#include "backends/graphics/opengl/debug.h"
+#include "backends/graphics/opengl/opengl-sys.h"
+
+#include "common/str.h"
+#include "common/textconsole.h"
+
+#ifdef OPENGL_DEBUG
+
+namespace OpenGL {
+
+namespace {
+Common::String getGLErrStr(GLenum error) {
+	switch (error) {
+	case GL_INVALID_ENUM:
+		return "GL_INVALID_ENUM";
+	case GL_INVALID_VALUE:
+		return "GL_INVALID_VALUE";
+	case GL_INVALID_OPERATION:
+		return "GL_INVALID_OPERATION";
+	case GL_STACK_OVERFLOW:
+		return "GL_STACK_OVERFLOW";
+	case GL_STACK_UNDERFLOW:
+		return "GL_STACK_UNDERFLOW";
+	case GL_OUT_OF_MEMORY:
+		return "GL_OUT_OF_MEMORY";
+	}
+
+	return Common::String::format("(Unknown GL error code 0x%X)", error);
+}
+} // End of anonymous namespace
+
+void checkGLError(const char *expr, const char *file, int line) {
+	GLenum error;
+
+	while ((error = glGetError()) != GL_NO_ERROR) {
+		// We cannot use error here because we do not know whether we have a
+		// working screen or not.
+		warning("GL ERROR: %s on %s (%s:%d)", getGLErrStr(error).c_str(), expr, file, line);
+	}
+}
+} // End of namespace OpenGL
+
+#endif
diff --git a/backends/graphics/opengl/debug.h b/backends/graphics/opengl/debug.h
new file mode 100644
index 0000000000..ff6b678870
--- /dev/null
+++ b/backends/graphics/opengl/debug.h
@@ -0,0 +1,39 @@
+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+#ifndef BACKENDS_GRAPHICS_OPENGL_DEBUG_H
+#define BACKENDS_GRAPHICS_OPENGL_DEBUG_H
+
+#define OPENGL_DEBUG
+
+#ifdef OPENGL_DEBUG
+
+namespace OpenGL {
+void checkGLError(const char *expr, const char *file, int line);
+} // End of namespace OpenGL
+
+#define GLCALL(x) do { (x); OpenGL::checkGLError(#x, __FILE__, __LINE__); } while (false)
+#else
+#define GLCALL(x) do { (x); } while (false)
+#endif
+
+#endif
diff --git a/backends/graphics/opengl/extensions.cpp b/backends/graphics/opengl/extensions.cpp
new file mode 100644
index 0000000000..4482ef82b5
--- /dev/null
+++ b/backends/graphics/opengl/extensions.cpp
@@ -0,0 +1,48 @@
+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+#include "backends/graphics/opengl/extensions.h"
+#include "backends/graphics/opengl/opengl-sys.h"
+
+#include "common/tokenizer.h"
+
+namespace OpenGL {
+
+bool g_extNPOTSupported = false;
+
+void initializeGLExtensions() {
+	const char *extString = (const char *)glGetString(GL_EXTENSIONS);
+
+	// Initialize default state.
+	g_extNPOTSupported = false;
+
+	Common::StringTokenizer tokenizer(extString, " ");
+	while (!tokenizer.empty()) {
+		Common::String token = tokenizer.nextToken();
+
+		if (token == "GL_ARB_texture_non_power_of_two") {
+			g_extNPOTSupported = true;
+		}
+	}
+}
+
+} // End of namespace OpenGL
diff --git a/backends/graphics/opengl/glerrorcheck.h b/backends/graphics/opengl/extensions.h
index 2d5491bdfd..87452429e2 100644
--- a/backends/graphics/opengl/glerrorcheck.h
+++ b/backends/graphics/opengl/extensions.h
@@ -8,28 +8,34 @@
  * modify it under the terms of the GNU General Public License
  * as published by the Free Software Foundation; either version 2
  * of the License, or (at your option) any later version.
-
+ *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
-
+ *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  *
  */
 
-#if !defined(DEBUG)
+#ifndef BACKENDS_GRAPHICS_OPENGL_EXTENSIONS_H
+#define BACKENDS_GRAPHICS_OPENGL_EXTENSIONS_H
 
-// If not in debug, do nothing
-#define CHECK_GL_ERROR() do {} while (false)
+namespace OpenGL {
 
-#else
+/**
+ * Checks for availability of extensions we want to use and initializes them
+ * when available.
+ */
+void initializeGLExtensions();
 
-// If in debug, check for an error after a GL call
-#define CHECK_GL_ERROR() checkGlError(__FILE__, __LINE__)
+/**
+ * Whether non power of two textures are supported
+ */
+extern bool g_extNPOTSupported;
 
-void checkGlError(const char *file, int line);
+} // End of namespace OpenGL
 
 #endif
diff --git a/backends/graphics/opengl/gltexture.cpp b/backends/graphics/opengl/gltexture.cpp
deleted file mode 100644
index ca674563df..0000000000
--- a/backends/graphics/opengl/gltexture.cpp
+++ /dev/null
@@ -1,225 +0,0 @@
-/* ScummVM - Graphic Adventure Engine
- *
- * ScummVM is the legal property of its developers, whose names
- * are too numerous to list here. Please refer to the COPYRIGHT
- * file distributed with this source distribution.
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version 2
- * of the License, or (at your option) any later version.
-
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
- * GNU General Public License for more details.
-
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
- *
- */
-
-#include "common/scummsys.h"
-
-#if defined(USE_OPENGL)
-
-#include "backends/graphics/opengl/gltexture.h"
-#include "backends/graphics/opengl/glerrorcheck.h"
-
-#include "common/rect.h"
-#include "common/array.h"
-#include "common/util.h"
-#include "common/tokenizer.h"
-
-// Supported GL extensions
-static bool npot_supported = false;
-static bool glext_inited = false;
-
-/*static inline GLint xdiv(int numerator, int denominator) {
-	assert(numerator < (1 << 16));
-	return (numerator << 16) / denominator;
-}*/
-
-static GLuint nextHigher2(GLuint v) {
-	if (v == 0)
-		return 1;
-	v--;
-	v |= v >> 1;
-	v |= v >> 2;
-	v |= v >> 4;
-	v |= v >> 8;
-	v |= v >> 16;
-	return ++v;
-}
-
-void GLTexture::initGLExtensions() {
-
-	// Return if extensions were already checked
-	if (glext_inited)
-		return;
-
-	// Get a string with all extensions
-	const char *ext_string = (const char *)glGetString(GL_EXTENSIONS);
-	CHECK_GL_ERROR();
-	Common::StringTokenizer tokenizer(ext_string, " ");
-	// Iterate all string tokens
-	while (!tokenizer.empty()) {
-		Common::String token = tokenizer.nextToken();
-		if (token == "GL_ARB_texture_non_power_of_two")
-			npot_supported = true;
-	}
-
-	glext_inited = true;
-}
-
-GLTexture::GLTexture(byte bpp, GLenum internalFormat, GLenum format, GLenum type)
-	:
-	_bytesPerPixel(bpp),
-	_internalFormat(internalFormat),
-	_glFormat(format),
-	_glType(type),
-	_textureWidth(0),
-	_textureHeight(0),
-	_realWidth(0),
-	_realHeight(0),
-	_refresh(false),
-	_filter(GL_NEAREST) {
-
-	// Generate the texture ID
-	glGenTextures(1, &_textureName); CHECK_GL_ERROR();
-}
-
-GLTexture::~GLTexture() {
-	// Delete the texture
-	glDeleteTextures(1, &_textureName); CHECK_GL_ERROR();
-}
-
-void GLTexture::refresh() {
-	// Delete previous texture
-	glDeleteTextures(1, &_textureName); CHECK_GL_ERROR();
-
-	// Generate the texture ID
-	glGenTextures(1, &_textureName); CHECK_GL_ERROR();
-	_refresh = true;
-}
-
-void GLTexture::allocBuffer(GLuint w, GLuint h) {
-	_realWidth = w;
-	_realHeight = h;
-
-	if (!_refresh) {
-		if (npot_supported && _filter == GL_LINEAR) {
-			// Check if we already allocated a correctly-sized buffer
-			// This is so we don't need to duplicate the last row/column
-			if (w == _textureWidth && h == _textureHeight)
-				return;
-		} else {
-			// Check if we already have a large enough buffer
-			if (w <= _textureWidth && h <= _textureHeight)
-				return;
-		}
-	}
-
-	if (npot_supported) {
-		_textureWidth = w;
-		_textureHeight = h;
-	} else {
-		_textureWidth = nextHigher2(w);
-		_textureHeight = nextHigher2(h);
-	}
-
-	// Select this OpenGL texture
-	glBindTexture(GL_TEXTURE_2D, _textureName); CHECK_GL_ERROR();
-
-	// Set the texture parameters
-	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, _filter); CHECK_GL_ERROR();
-	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, _filter); CHECK_GL_ERROR();
-	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE); CHECK_GL_ERROR();
-	glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE); CHECK_GL_ERROR();
-
-	// Allocate room for the texture
-	glTexImage2D(GL_TEXTURE_2D, 0, _internalFormat,
-	             _textureWidth, _textureHeight, 0, _glFormat, _glType, NULL); CHECK_GL_ERROR();
-
-	_refresh = false;
-}
-
-void GLTexture::updateBuffer(const void *buf, int pitch, GLuint x, GLuint y, GLuint w, GLuint h) {
-	// Skip empty updates.
-	if (w * h == 0)
-		return;
-
-	// Select this OpenGL texture
-	glBindTexture(GL_TEXTURE_2D, _textureName); CHECK_GL_ERROR();
-
-	// Check if the buffer has its data contiguously
-	if ((int)w * _bytesPerPixel == pitch) {
-		glTexSubImage2D(GL_TEXTURE_2D, 0, x, y, w, h,
-		                _glFormat, _glType, buf); CHECK_GL_ERROR();
-	} else {
-		// Update the texture row by row
-		const byte *src = (const byte *)buf;
-		GLuint curY = y;
-		GLuint height = h;
-		do {
-			glTexSubImage2D(GL_TEXTURE_2D, 0, x, curY,
-			                w, 1, _glFormat, _glType, src); CHECK_GL_ERROR();
-			curY++;
-			src += pitch;
-		} while (--height);
-	}
-
-	// If we're in linear filter mode, repeat the last row/column if the real dimensions
-	// doesn't match the texture dimensions.
-	if (_filter == GL_LINEAR) {
-		if (_realWidth != _textureWidth && x + w == _realWidth) {
-			const byte *src = (const byte *)buf + (w - 1) * _bytesPerPixel;
-			GLuint curY = y;
-			GLuint height = h;
-
-			do {
-				glTexSubImage2D(GL_TEXTURE_2D, 0, x + w,
-						curY, 1, 1, _glFormat, _glType, src); CHECK_GL_ERROR();
-
-				curY++;
-				src += pitch;
-			} while (--height);
-		}
-
-		if (_realHeight != _textureHeight && y + h == _realHeight) {
-			glTexSubImage2D(GL_TEXTURE_2D, 0, x, y + h,
-					w, 1, _glFormat, _glType, (const byte *)buf + pitch * (h - 1)); CHECK_GL_ERROR();
-		}
-	}
-}
-
-void GLTexture::drawTexture(GLshort x, GLshort y, GLshort w, GLshort h) {
-	// Select this OpenGL texture
-	glBindTexture(GL_TEXTURE_2D, _textureName); CHECK_GL_ERROR();
-
-	// Calculate the texture rect that will be drawn
-	const GLfloat texWidth = (GLfloat)_realWidth / _textureWidth;//xdiv(_surface.w, _textureWidth);
-	const GLfloat texHeight = (GLfloat)_realHeight / _textureHeight;//xdiv(_surface.h, _textureHeight);
-	const GLfloat texcoords[] = {
-		0, 0,
-		texWidth, 0,
-		0, texHeight,
-		texWidth, texHeight,
-	};
-	glTexCoordPointer(2, GL_FLOAT, 0, texcoords); CHECK_GL_ERROR();
-
-	// Calculate the screen rect where the texture will be drawn
-	const GLshort vertices[] = {
-		x,                y,
-		(GLshort)(x + w), y,
-		x,                (GLshort)(y + h),
-		(GLshort)(x + w), (GLshort)(y + h),
-	};
-	glVertexPointer(2, GL_SHORT, 0, vertices); CHECK_GL_ERROR();
-
-	// Draw the texture to the screen buffer
-	glDrawArrays(GL_TRIANGLE_STRIP, 0, 4); CHECK_GL_ERROR();
-}
-
-#endif
diff --git a/backends/graphics/opengl/gltexture.h b/backends/graphics/opengl/gltexture.h
deleted file mode 100644
index 6ef80923ae..0000000000
--- a/backends/graphics/opengl/gltexture.h
+++ /dev/null
@@ -1,131 +0,0 @@
-/* ScummVM - Graphic Adventure Engine
- *
- * ScummVM is the legal property of its developers, whose names
- * are too numerous to list here. Please refer to the COPYRIGHT
- * file distributed with this source distribution.
- *
- * This program is free software; you can redistribute it and/or
- * modify it under the terms of the GNU General Public License
- * as published by the Free Software Foundation; either version 2
- * of the License, or (at your option) any later version.
-
- * This program is distributed in the hope that it will be useful,
- * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
- * GNU General Public License for more details.
-
- * You should have received a copy of the GNU General Public License
- * along with this program; if not, write to the Free Software
- * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
- *
- */
-
-#ifndef BACKENDS_GRAPHICS_OPENGL_GLTEXTURE_H
-#define BACKENDS_GRAPHICS_OPENGL_GLTEXTURE_H
-
-#include "common/scummsys.h"
-
-#ifdef WIN32
-#if defined(ARRAYSIZE) && !defined(_WINDOWS_)
-#undef ARRAYSIZE
-#endif
-#define WIN32_LEAN_AND_MEAN
-#include <windows.h>
-#undef ARRAYSIZE
-#endif
-
-// HACK: At this point in Windows platforms, common/util.h has been included
-// via common/rect.h (from backends/graphics/sdl/sdl-graphics.h), via
-// backends/graphics/openglsdl/openglsdl-graphics.h. Thus, we end up with
-// COMMON_UTIL_H defined, and ARRAYSIZE undefined (bad!). Therefore,
-// ARRAYSIZE is undefined in openglsdl-graphics.cpp. This is a temporary
-// hackish solution fo fix compilation under Windows.
-#if !defined(ARRAYSIZE) && defined(COMMON_UTIL_H)
-#define ARRAYSIZE(x) ((int)(sizeof(x) / sizeof(x[0])))
-#endif
-
-#if defined(TIZEN)
-#include <FGraphicsOpengl.h>
-using namespace Tizen::Graphics::Opengl;
-#elif defined(USE_GLES)
-#include <GLES/gl.h>
-#elif defined(SDL_BACKEND)
-#include <SDL_opengl.h>
-#else
-#include <GL/gl.h>
-#endif
-
-#include "graphics/surface.h"
-
-/**
- * OpenGL texture manager class
- */
-class GLTexture {
-public:
-	/**
-	 * Initialize OpenGL Extensions
-	 */
-	static void initGLExtensions();
-
-	GLTexture(byte bpp, GLenum internalFormat, GLenum format, GLenum type);
-	~GLTexture();
-
-	/**
-	 * Refresh the texture after a context change. The
-	 * process will be completed on next allocBuffer call.
-	 */
-	void refresh();
-
-	/**
-	 * Allocates memory needed for the given size.
-	 */
-	void allocBuffer(GLuint width, GLuint height);
-
-	/**
-	 * Updates the texture pixels.
-	 */
-	void updateBuffer(const void *buf, int pitch, GLuint x, GLuint y,
-		GLuint w, GLuint h);
-
-	/**
-	 * Draws the texture to the screen buffer.
-	 */
-	void drawTexture(GLshort x, GLshort y, GLshort w, GLshort h);
-
-	/**
-	 * Get the texture width.
-	 */
-	GLuint getWidth() const { return _realWidth; }
-
-	/**
-	 * Get the texture height.
-	 */
-	GLuint getHeight() const { return _realHeight; }
-
-	/**
-	 * Get the bytes per pixel.
-	 */
-	uint getBytesPerPixel() const { return _bytesPerPixel; }
-
-	/**
-	 * Set the texture filter.
-	 * @filter the filter type, GL_NEAREST or GL_LINEAR
-	 */
-	void setFilter(GLint filter) { _filter = filter; }
-
-private:
-	const byte _bytesPerPixel;
-	const GLenum _internalFormat;
-	const GLenum _glFormat;
-	const GLenum _glType;
-
-	GLuint _realWidth;
-	GLuint _realHeight;
-	GLuint _textureName;
-	GLuint _textureWidth;
-	GLuint _textureHeight;
-	GLint _filter;
-	bool _refresh;
-};
-
-#endif
diff --git a/backends/graphics/opengl/opengl-graphics.cpp b/backends/graphics/opengl/opengl-graphics.cpp
index 84be83d524..cbd06e9161 100644
--- a/backends/graphics/opengl/opengl-graphics.cpp
+++ b/backends/graphics/opengl/opengl-graphics.cpp
@@ -8,102 +8,90 @@
  * modify it under the terms of the GNU General Public License
  * as published by the Free Software Foundation; either version 2
  * of the License, or (at your option) any later version.
-
+ *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
-
+ *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  *
  */
 
-#include "common/scummsys.h"
-
-#if defined(USE_OPENGL)
 
 #include "backends/graphics/opengl/opengl-graphics.h"
-#include "backends/graphics/opengl/glerrorcheck.h"
-#include "common/config-manager.h"
-#include "common/file.h"
-#include "common/mutex.h"
+#include "backends/graphics/opengl/texture.h"
+#include "backends/graphics/opengl/debug.h"
+#include "backends/graphics/opengl/extensions.h"
+
 #include "common/textconsole.h"
 #include "common/translation.h"
+#include "common/algorithm.h"
+#include "common/file.h"
 #ifdef USE_OSD
 #include "common/tokenizer.h"
+#include "common/rect.h"
 #endif
-#include "graphics/font.h"
+
+#include "graphics/conversion.h"
+#ifdef USE_OSD
 #include "graphics/fontman.h"
+#include "graphics/font.h"
+#endif
+
+namespace OpenGL {
 
 OpenGLGraphicsManager::OpenGLGraphicsManager()
-	:
+    : _currentState(), _oldState(), _transactionMode(kTransactionNone), _screenChangeID(1 << (sizeof(int) * 8 - 2)),
+      _outputScreenWidth(0), _outputScreenHeight(0), _displayX(0), _displayY(0),
+      _displayWidth(0), _displayHeight(0), _defaultFormat(), _defaultFormatAlpha(),
+      _gameScreen(nullptr), _gameScreenShakeOffset(0), _overlay(nullptr),
+      _overlayVisible(false), _cursor(nullptr),
+      _cursorX(0), _cursorY(0), _cursorHotspotX(0), _cursorHotspotY(0), _cursorHotspotXScaled(0),
+      _cursorHotspotYScaled(0), _cursorWidthScaled(0), _cursorHeightScaled(0), _cursorKeyColor(0),
+      _cursorVisible(false), _cursorDontScale(false), _cursorPaletteEnabled(false)
 #ifdef USE_OSD
-	_osdTexture(0), _osdAlpha(0), _osdFadeStartTime(0), _requireOSDUpdate(false),
+      , _osdAlpha(0), _osdFadeStartTime(0), _osd(nullptr)
 #endif
-	_gameTexture(0), _overlayTexture(0), _cursorTexture(0),
-	_screenChangeCount(1 << (sizeof(int) * 8 - 2)), _screenNeedsRedraw(false),
-	_shakePos(0),
-	_overlayVisible(false), _overlayNeedsRedraw(false),
-	_transactionMode(kTransactionNone),
-	_cursorNeedsRedraw(false), _cursorPaletteDisabled(true),
-	_cursorVisible(false), _cursorKeyColor(0),
-	_cursorDontScale(false),
-	_formatBGR(false),
-	_displayX(0), _displayY(0), _displayWidth(0), _displayHeight(0) {
-
-	memset(&_oldVideoMode, 0, sizeof(_oldVideoMode));
-	memset(&_videoMode, 0, sizeof(_videoMode));
-	memset(&_transactionDetails, 0, sizeof(_transactionDetails));
-
-	_videoMode.mode = OpenGL::GFX_NORMAL;
-	_videoMode.scaleFactor = 2;
-	_videoMode.fullscreen = ConfMan.getBool("fullscreen");
-	_videoMode.antialiasing = false;
-
-	_gamePalette = (byte *)calloc(sizeof(byte) * 3, 256);
-	_cursorPalette = (byte *)calloc(sizeof(byte) * 3, 256);
+    {
+	memset(_gamePalette, 0, sizeof(_gamePalette));
 }
 
 OpenGLGraphicsManager::~OpenGLGraphicsManager() {
-	free(_gamePalette);
-	free(_cursorPalette);
-
-	_screenData.free();
-	_overlayData.free();
-	_cursorData.free();
-	_osdSurface.free();
-
-	delete _gameTexture;
-	delete _overlayTexture;
-	delete _cursorTexture;
+	delete _gameScreen;
+	delete _overlay;
+	delete _cursor;
+#ifdef USE_OSD
+	delete _osd;
+#endif
 }
 
-//
-// Feature
-//
-
 bool OpenGLGraphicsManager::hasFeature(OSystem::Feature f) {
-	return
-	    (f == OSystem::kFeatureAspectRatioCorrection) ||
-	    (f == OSystem::kFeatureCursorPalette);
+	switch (f) {
+	case OSystem::kFeatureAspectRatioCorrection:
+	case OSystem::kFeatureCursorPalette:
+		return true;
+
+	case OSystem::kFeatureOverlaySupportsAlpha:
+		return _defaultFormatAlpha.aBits() > 3;
+
+	default:
+		return false;
+	}
 }
 
 void OpenGLGraphicsManager::setFeatureState(OSystem::Feature f, bool enable) {
 	switch (f) {
-	case OSystem::kFeatureFullscreenMode:
-		setFullscreenMode(enable);
-		break;
-
 	case OSystem::kFeatureAspectRatioCorrection:
-		_videoMode.aspectRatioCorrection = enable;
-		_transactionDetails.needRefresh = true;
+		assert(_transactionMode != kTransactionNone);
+		_currentState.aspectRatioCorrection = enable;
 		break;
 
 	case OSystem::kFeatureCursorPalette:
-		_cursorPaletteDisabled = !enable;
-		_cursorNeedsRedraw = true;
+		_cursorPaletteEnabled = enable;
+		updateCursorPalette();
 		break;
 
 	default:
@@ -113,1189 +101,1038 @@ void OpenGLGraphicsManager::setFeatureState(OSystem::Feature f, bool enable) {
 
 bool OpenGLGraphicsManager::getFeatureState(OSystem::Feature f) {
 	switch (f) {
-	case OSystem::kFeatureFullscreenMode:
-		return _videoMode.fullscreen;
-
 	case OSystem::kFeatureAspectRatioCorrection:
-		return _videoMode.aspectRatioCorrection;
+		return _currentState.aspectRatioCorrection;
 
 	case OSystem::kFeatureCursorPalette:
-		return !_cursorPaletteDisabled;
+		return _cursorPaletteEnabled;
 
 	default:
 		return false;
 	}
 }
 
-//
-// Screen format and modes
-//
+namespace {
 
-static const OSystem::GraphicsMode s_supportedGraphicsModes[] = {
-	{"gl1", _s("OpenGL Normal"), OpenGL::GFX_NORMAL},
-	{"gl2", _s("OpenGL Conserve"), OpenGL::GFX_CONSERVE},
-	{"gl4", _s("OpenGL Original"), OpenGL::GFX_ORIGINAL},
-	{0, 0, 0}
+const OSystem::GraphicsMode glGraphicsModes[] = {
+	{ "opengl_linear",  _s("OpenGL"),                GFX_LINEAR  },
+	{ "opengl_nearest", _s("OpenGL (No filtering)"), GFX_NEAREST },
+	{ nullptr, nullptr, 0 }
 };
 
-const OSystem::GraphicsMode *OpenGLGraphicsManager::supportedGraphicsModes() {
-	return s_supportedGraphicsModes;
-}
+} // End of anonymous namespace
 
 const OSystem::GraphicsMode *OpenGLGraphicsManager::getSupportedGraphicsModes() const {
-	return s_supportedGraphicsModes;
+	return glGraphicsModes;
 }
 
 int OpenGLGraphicsManager::getDefaultGraphicsMode() const {
-	return OpenGL::GFX_NORMAL;
+	return GFX_LINEAR;
 }
 
 bool OpenGLGraphicsManager::setGraphicsMode(int mode) {
-	assert(_transactionMode == kTransactionActive);
+	assert(_transactionMode != kTransactionNone);
 
-	setScale(2);
+	switch (mode) {
+	case GFX_LINEAR:
+	case GFX_NEAREST:
+		_currentState.graphicsMode = mode;
+
+		if (_gameScreen) {
+			_gameScreen->enableLinearFiltering(mode == GFX_LINEAR);
+		}
+
+		if (_cursor) {
+			_cursor->enableLinearFiltering(mode == GFX_LINEAR);
+		}
 
-	if (_oldVideoMode.setup && _oldVideoMode.mode == mode)
 		return true;
 
-	switch (mode) {
-	case OpenGL::GFX_NORMAL:
-	case OpenGL::GFX_CONSERVE:
-	case OpenGL::GFX_ORIGINAL:
-		break;
 	default:
-		warning("Unknown gfx mode %d", mode);
+		warning("OpenGLGraphicsManager::setGraphicsMode(%d): Unknown graphics mode", mode);
 		return false;
 	}
-
-	_videoMode.mode = mode;
-	_transactionDetails.needRefresh = true;
-
-	return true;
 }
 
 int OpenGLGraphicsManager::getGraphicsMode() const {
-	assert(_transactionMode == kTransactionNone);
-	return _videoMode.mode;
-}
-
-void OpenGLGraphicsManager::resetGraphicsScale() {
-	setScale(1);
+	return _currentState.graphicsMode;
 }
 
 #ifdef USE_RGB_COLOR
 Graphics::PixelFormat OpenGLGraphicsManager::getScreenFormat() const {
-	return _screenFormat;
+	return _currentState.gameFormat;
 }
 #endif
 
-void OpenGLGraphicsManager::initSize(uint width, uint height, const Graphics::PixelFormat *format) {
-	assert(_transactionMode == kTransactionActive);
-
-#ifdef USE_RGB_COLOR
-	Graphics::PixelFormat newFormat;
-	if (!format)
-		newFormat = Graphics::PixelFormat::createFormatCLUT8();
-	else
-		newFormat = *format;
-
-	assert(newFormat.bytesPerPixel > 0);
-
-	// Avoid redundant format changes
-	if (newFormat != _videoMode.format) {
-		_videoMode.format = newFormat;
-		_transactionDetails.formatChanged = true;
-		_screenFormat = newFormat;
-	}
-#endif
-
-	// Avoid redundant res changes
-	if ((int)width == _videoMode.screenWidth && (int)height == _videoMode.screenHeight)
-		return;
-
-	_videoMode.screenWidth = width;
-	_videoMode.screenHeight = height;
+void OpenGLGraphicsManager::beginGFXTransaction() {
+	assert(_transactionMode == kTransactionNone);
 
-	_transactionDetails.sizeChanged = true;
+	// Start a transaction.
+	_oldState = _currentState;
+	_transactionMode = kTransactionActive;
 }
 
-int OpenGLGraphicsManager::getScreenChangeID() const {
-	return _screenChangeCount;
-}
+OSystem::TransactionError OpenGLGraphicsManager::endGFXTransaction() {
+	assert(_transactionMode == kTransactionActive);
 
-//
-// GFX
-//
+	uint transactionError = OSystem::kTransactionSuccess;
 
-void OpenGLGraphicsManager::beginGFXTransaction() {
-	assert(_transactionMode == kTransactionNone);
+	bool setupNewGameScreen = false;
+	if (   _oldState.gameWidth  != _currentState.gameWidth
+	    || _oldState.gameHeight != _currentState.gameHeight) {
+		setupNewGameScreen = true;
+	}
 
-	_transactionMode = kTransactionActive;
-	_transactionDetails.sizeChanged = false;
-	_transactionDetails.needRefresh = false;
-	_transactionDetails.needUpdatescreen = false;
-	_transactionDetails.filterChanged = false;
 #ifdef USE_RGB_COLOR
-	_transactionDetails.formatChanged = false;
+	if (_oldState.gameFormat != _currentState.gameFormat) {
+		setupNewGameScreen = true;
+	}
+
+	// Check whether the requested format can actually be used.
+	Common::List<Graphics::PixelFormat> supportedFormats = getSupportedFormats();
+	// In case the requested format is not usable we will fall back to CLUT8.
+	if (Common::find(supportedFormats.begin(), supportedFormats.end(), _currentState.gameFormat) == supportedFormats.end()) {
+		_currentState.gameFormat = Graphics::PixelFormat::createFormatCLUT8();
+		transactionError |= OSystem::kTransactionFormatNotSupported;
+	}
 #endif
 
-	_oldVideoMode = _videoMode;
-}
+	do {
+		uint requestedWidth  = _currentState.gameWidth;
+		uint requestedHeight = _currentState.gameHeight;
+		const uint desiredAspect = getDesiredGameScreenAspect();
+		requestedHeight = intToFrac(requestedWidth) / desiredAspect;
 
-OSystem::TransactionError OpenGLGraphicsManager::endGFXTransaction() {
-	int errors = OSystem::kTransactionSuccess;
+		if (!loadVideoMode(requestedWidth, requestedHeight,
+#ifdef USE_RGB_COLOR
+		                   _currentState.gameFormat
+#else
+		                   Graphics::PixelFormat::createFormatCLUT8()
+#endif
+		                  )
+		   // HACK: This is really nasty but we don't have any guarantees of
+		   // a context existing before, which means we don't know the maximum
+		   // supported texture size before this. Thus, we check whether the
+		   // requested game resolution is supported over here.
+		   || (   _currentState.gameWidth  > (uint)Texture::getMaximumTextureSize()
+		       || _currentState.gameHeight > (uint)Texture::getMaximumTextureSize())) {
+			if (_transactionMode == kTransactionActive) {
+				// Try to setup the old state in case its valid and is
+				// actually different from the new one.
+				if (_oldState.valid && _oldState != _currentState) {
+					// Give some hints on what failed to set up.
+					if (   _oldState.gameWidth  != _currentState.gameWidth
+					    || _oldState.gameHeight != _currentState.gameHeight) {
+						transactionError |= OSystem::kTransactionSizeChangeFailed;
+					}
 
-	assert(_transactionMode != kTransactionNone);
+#ifdef USE_RGB_COLOR
+					if (_oldState.gameFormat != _currentState.gameFormat) {
+						transactionError |= OSystem::kTransactionFormatNotSupported;
+					}
+#endif
 
-	if (_transactionMode == kTransactionRollback) {
-		if (_videoMode.fullscreen != _oldVideoMode.fullscreen) {
-			errors |= OSystem::kTransactionFullscreenFailed;
+					if (_oldState.aspectRatioCorrection != _currentState.aspectRatioCorrection) {
+						transactionError |= OSystem::kTransactionAspectRatioFailed;
+					}
 
-			_videoMode.fullscreen = _oldVideoMode.fullscreen;
-		} else if (_videoMode.mode != _oldVideoMode.mode) {
-			errors |= OSystem::kTransactionModeSwitchFailed;
+					if (_oldState.graphicsMode != _currentState.graphicsMode) {
+						transactionError |= OSystem::kTransactionModeSwitchFailed;
+					}
 
-			_videoMode.mode = _oldVideoMode.mode;
-			_videoMode.scaleFactor = _oldVideoMode.scaleFactor;
-#ifdef USE_RGB_COLOR
-		} else if (_videoMode.format != _oldVideoMode.format) {
-			errors |= OSystem::kTransactionFormatNotSupported;
+					// Roll back to the old state.
+					_currentState = _oldState;
+					_transactionMode = kTransactionRollback;
 
-			_videoMode.format = _oldVideoMode.format;
-			_screenFormat = _videoMode.format;
-#endif
-		} else if (_videoMode.screenWidth != _oldVideoMode.screenWidth || _videoMode.screenHeight != _oldVideoMode.screenHeight) {
-			errors |= OSystem::kTransactionSizeChangeFailed;
+					// Try to set up the old state.
+					continue;
+				}
+			}
 
-			_videoMode.screenWidth = _oldVideoMode.screenWidth;
-			_videoMode.screenHeight = _oldVideoMode.screenHeight;
-			_videoMode.overlayWidth = _oldVideoMode.overlayWidth;
-			_videoMode.overlayHeight = _oldVideoMode.overlayHeight;
+			// DON'T use error(), as this tries to bring up the debug
+			// console, which WON'T WORK now that we might no have a
+			// proper screen.
+			warning("OpenGLGraphicsManager::endGFXTransaction: Could not load any graphics mode!");
+			g_system->quit();
 		}
 
-		if (_videoMode.fullscreen == _oldVideoMode.fullscreen &&
-		        _videoMode.mode == _oldVideoMode.mode &&
-		        _videoMode.screenWidth == _oldVideoMode.screenWidth &&
-		        _videoMode.screenHeight == _oldVideoMode.screenHeight) {
+		// In case we reach this we have a valid state, yay.
+		_transactionMode = kTransactionNone;
+		_currentState.valid = true;
+	} while (_transactionMode == kTransactionRollback);
+
+	if (setupNewGameScreen) {
+		delete _gameScreen;
+		_gameScreen = nullptr;
 
-			_oldVideoMode.setup = false;
+#ifdef USE_RGB_COLOR
+		_gameScreen = createTexture(_currentState.gameFormat);
+#else
+		_gameScreen = createTexture(Graphics::PixelFormat::createFormatCLUT8());
+#endif
+		assert(_gameScreen);
+		if (_gameScreen->hasPalette()) {
+			_gameScreen->setPalette(0, 256, _gamePalette);
 		}
-	}
 
-	if (_transactionDetails.sizeChanged || _transactionDetails.needRefresh) {
-		unloadGFXMode();
-		if (!loadGFXMode()) {
-			if (_oldVideoMode.setup) {
-				_transactionMode = kTransactionRollback;
-				errors |= endGFXTransaction();
-			}
+		_gameScreen->allocate(_currentState.gameWidth, _currentState.gameHeight);
+		_gameScreen->enableLinearFiltering(_currentState.graphicsMode == GFX_LINEAR);
+		// We fill the screen to all black or index 0 for CLUT8.
+#ifdef USE_RGB_COLOR
+		if (_currentState.gameFormat.bytesPerPixel == 1) {
+			_gameScreen->fill(0);
 		} else {
-			clearOverlay();
-
-			_videoMode.setup = true;
-			_screenChangeCount++;
+			_gameScreen->fill(_gameScreen->getSurface()->format.RGBToColor(0, 0, 0));
 		}
-#ifdef USE_RGB_COLOR
-	} else if (_transactionDetails.filterChanged || _transactionDetails.formatChanged) {
 #else
-	} else if (_transactionDetails.filterChanged) {
+		_gameScreen->fill(0);
 #endif
-		loadTextures();
-		internUpdateScreen();
-	} else if (_transactionDetails.needUpdatescreen) {
-		internUpdateScreen();
 	}
 
-	_transactionMode = kTransactionNone;
-	return (OSystem::TransactionError)errors;
-}
+	// Update our display area and cursor scaling. This makes sure we pick up
+	// aspect ratio correction and game screen changes correctly.
+	recalculateDisplayArea();
+	recalculateCursorScaling();
 
-//
-// Screen
-//
+	// Something changed, so update the screen change ID.
+	++_screenChangeID;
 
-int16 OpenGLGraphicsManager::getHeight() {
-	return _videoMode.screenHeight;
+	// Since transactionError is a ORd list of TransactionErrors this is
+	// clearly wrong. But our API is simply broken.
+	return (OSystem::TransactionError)transactionError;
 }
 
-int16 OpenGLGraphicsManager::getWidth() {
-	return _videoMode.screenWidth;
+int OpenGLGraphicsManager::getScreenChangeID() const {
+	return _screenChangeID;
 }
 
-void OpenGLGraphicsManager::setPalette(const byte *colors, uint start, uint num) {
-	assert(colors);
-
+void OpenGLGraphicsManager::initSize(uint width, uint height, const Graphics::PixelFormat *format) {
+	Graphics::PixelFormat requestedFormat;
 #ifdef USE_RGB_COLOR
-	assert(_screenFormat.bytesPerPixel == 1);
+	if (!format) {
+		requestedFormat = Graphics::PixelFormat::createFormatCLUT8();
+	} else {
+		requestedFormat = *format;
+	}
+	_currentState.gameFormat = requestedFormat;
 #endif
 
-	// Save the screen palette
-	memcpy(_gamePalette + start * 3, colors, num * 3);
+	_currentState.gameWidth = width;
+	_currentState.gameHeight = height;
+}
 
-	_screenNeedsRedraw = true;
+int16 OpenGLGraphicsManager::getWidth() {
+	return _currentState.gameWidth;
+}
 
-	if (_cursorPaletteDisabled)
-		_cursorNeedsRedraw = true;
+int16 OpenGLGraphicsManager::getHeight() {
+	return _currentState.gameHeight;
 }
 
-void OpenGLGraphicsManager::grabPalette(byte *colors, uint start, uint num) {
-	assert(colors);
+void OpenGLGraphicsManager::copyRectToScreen(const void *buf, int pitch, int x, int y, int w, int h) {
+	_gameScreen->copyRectToTexture(x, y, w, h, buf, pitch);
+}
 
-#ifdef USE_RGB_COLOR
-	assert(_screenFormat.bytesPerPixel == 1);
-#endif
+void OpenGLGraphicsManager::fillScreen(uint32 col) {
+	// FIXME: This does not conform to the OSystem specs because fillScreen
+	// is always taking CLUT8 color values and use color indexed mode. This is,
+	// however, plain odd and probably was a forgotten when we introduced
+	// RGB support. Thus, we simply do the "sane" thing here and hope OSystem
+	// gets fixed one day.
+	_gameScreen->fill(col);
+}
 
-	// Copies current palette to buffer
-	memcpy(colors, _gamePalette + start * 3, num * 3);
+void OpenGLGraphicsManager::setShakePos(int shakeOffset) {
+	_gameScreenShakeOffset = shakeOffset;
 }
 
-void OpenGLGraphicsManager::copyRectToScreen(const void *buf, int pitch, int x, int y, int w, int h) {
-	assert(x >= 0 && x < _screenData.w);
-	assert(y >= 0 && y < _screenData.h);
-	assert(h > 0 && y + h <= _screenData.h);
-	assert(w > 0 && x + w <= _screenData.w);
-
-	// Copy buffer data to game screen internal buffer
-	const byte *src = (const byte *)buf;
-	byte *dst = (byte *)_screenData.getBasePtr(x, y);
-	for (int i = 0; i < h; i++) {
-		memcpy(dst, src, w * _screenData.format.bytesPerPixel);
-		src += pitch;
-		dst += _screenData.pitch;
+void OpenGLGraphicsManager::updateScreen() {
+	if (!_gameScreen) {
+		return;
 	}
 
-	// Extend dirty area if not full screen redraw is flagged
-	if (!_screenNeedsRedraw) {
-		const Common::Rect dirtyRect(x, y, x + w, y + h);
-		_screenDirtyRect.extend(dirtyRect);
+	// Clear the screen buffer
+	GLCALL(glClear(GL_COLOR_BUFFER_BIT));
+
+	const GLfloat shakeOffset = _gameScreenShakeOffset * (GLfloat)_displayHeight / _gameScreen->getHeight();
+
+	// First step: Draw the (virtual) game screen.
+	_gameScreen->draw(_displayX, _displayY + shakeOffset, _displayWidth, _displayHeight);
+
+	// Second step: Draw the overlay if visible.
+	if (_overlayVisible) {
+		_overlay->draw(0, 0, _outputScreenWidth, _outputScreenHeight);
 	}
-}
 
-Graphics::Surface *OpenGLGraphicsManager::lockScreen() {
-	return &_screenData;
-}
+	// Third step: Draw the cursor if visible.
+	if (_cursorVisible && _cursor) {
+		// Adjust game screen shake position, but only when the overlay is not
+		// visible.
+		const GLfloat cursorOffset = _overlayVisible ? 0 : shakeOffset;
 
-void OpenGLGraphicsManager::unlockScreen() {
-	_screenNeedsRedraw = true;
-}
+		_cursor->draw(_cursorX - _cursorHotspotXScaled, _cursorY - _cursorHotspotYScaled + cursorOffset,
+		              _cursorWidthScaled, _cursorHeightScaled);
+	}
 
-void OpenGLGraphicsManager::fillScreen(uint32 col) {
-	if (_gameTexture == NULL)
-		return;
+#ifdef USE_OSD
+	// Fourth step: Draw the OSD.
+	if (_osdAlpha > 0) {
+		Common::StackLock lock(_osdMutex);
 
-#ifdef USE_RGB_COLOR
-	if (_screenFormat.bytesPerPixel == 1) {
-		memset(_screenData.getPixels(), col, _screenData.h * _screenData.pitch);
-	} else if (_screenFormat.bytesPerPixel == 2) {
-		uint16 *pixels = (uint16 *)_screenData.getPixels();
-		uint16 col16 = (uint16)col;
-		for (int i = 0; i < _screenData.w * _screenData.h; i++) {
-			pixels[i] = col16;
-		}
-	} else if (_screenFormat.bytesPerPixel == 3) {
-		uint8 *pixels = (uint8 *)_screenData.getPixels();
-		byte r = (col >> 16) & 0xFF;
-		byte g = (col >> 8) & 0xFF;
-		byte b = col & 0xFF;
-		for (int i = 0; i < _screenData.w * _screenData.h; i++) {
-			pixels[0] = r;
-			pixels[1] = g;
-			pixels[2] = b;
-			pixels += 3;
-		}
-	} else if (_screenFormat.bytesPerPixel == 4) {
-		uint32 *pixels = (uint32 *)_screenData.getPixels();
-		for (int i = 0; i < _screenData.w * _screenData.h; i++) {
-			pixels[i] = col;
+		// Update alpha value.
+		const int diff = g_system->getMillis(false) - _osdFadeStartTime;
+		if (diff > 0) {
+			if (diff >= kOSDFadeOutDuration) {
+				// Back to full transparency.
+				_osdAlpha = 0;
+			} else {
+				// Do a fade out.
+				_osdAlpha = kOSDInitialAlpha - diff * kOSDInitialAlpha / kOSDFadeOutDuration;
+			}
 		}
+
+		// Set the OSD transparency.
+		GLCALL(glColor4f(1.0f, 1.0f, 1.0f, _osdAlpha / 100.0f));
+
+		// Draw the OSD texture.
+		_osd->draw(0, 0, _outputScreenWidth, _outputScreenHeight);
+
+		// Reset color.
+		GLCALL(glColor4f(1.0f, 1.0f, 1.0f, 1.0f));
 	}
-#else
-	memset(_screenData.getPixels(), col, _screenData.h * _screenData.pitch);
 #endif
-	_screenNeedsRedraw = true;
 }
 
-void OpenGLGraphicsManager::updateScreen() {
-	assert(_transactionMode == kTransactionNone);
-	internUpdateScreen();
+Graphics::Surface *OpenGLGraphicsManager::lockScreen() {
+	return _gameScreen->getSurface();
 }
 
-void OpenGLGraphicsManager::setShakePos(int shakeOffset) {
-	assert(_transactionMode == kTransactionNone);
-	_shakePos = shakeOffset;
+void OpenGLGraphicsManager::unlockScreen() {
+	_gameScreen->flagDirty();
 }
 
-void OpenGLGraphicsManager::setFocusRectangle(const Common::Rect &rect) {
+void OpenGLGraphicsManager::setFocusRectangle(const Common::Rect& rect) {
 }
 
 void OpenGLGraphicsManager::clearFocusRectangle() {
 }
 
-//
-// Overlay
-//
-
-void OpenGLGraphicsManager::showOverlay() {
-	assert(_transactionMode == kTransactionNone);
+int16 OpenGLGraphicsManager::getOverlayWidth() {
+	if (_overlay) {
+		return _overlay->getWidth();
+	} else {
+		return 0;
+	}
+}
 
-	if (_overlayVisible)
-		return;
+int16 OpenGLGraphicsManager::getOverlayHeight() {
+	if (_overlay) {
+		return _overlay->getHeight();
+	} else {
+		return 0;
+	}
+}
 
+void OpenGLGraphicsManager::showOverlay() {
 	_overlayVisible = true;
-
-	clearOverlay();
 }
 
 void OpenGLGraphicsManager::hideOverlay() {
-	assert(_transactionMode == kTransactionNone);
-
-	if (!_overlayVisible)
-		return;
-
 	_overlayVisible = false;
-
-	clearOverlay();
 }
 
 Graphics::PixelFormat OpenGLGraphicsManager::getOverlayFormat() const {
-	return _overlayFormat;
+	return _overlay->getFormat();
 }
 
-void OpenGLGraphicsManager::clearOverlay() {
-	// Set all pixels to 0
-	memset(_overlayData.getPixels(), 0, _overlayData.h * _overlayData.pitch);
-	_overlayNeedsRedraw = true;
+void OpenGLGraphicsManager::copyRectToOverlay(const void *buf, int pitch, int x, int y, int w, int h) {
+	_overlay->copyRectToTexture(x, y, w, h, buf, pitch);
 }
 
-void OpenGLGraphicsManager::grabOverlay(void *buf, int pitch) {
-	const byte *src = (byte *)_overlayData.getPixels();
-	byte *dst = (byte *)buf;
-	for (int i = 0; i < _overlayData.h; i++) {
-		// Copy overlay data to buffer
-		memcpy(dst, src, _overlayData.pitch);
-		dst += pitch;
-		src += _overlayData.pitch;
-	}
+void OpenGLGraphicsManager::clearOverlay() {
+	_overlay->fill(0);
 }
 
-void OpenGLGraphicsManager::copyRectToOverlay(const void *buf, int pitch, int x, int y, int w, int h) {
-	assert(_transactionMode == kTransactionNone);
-
-	if (_overlayTexture == NULL)
-		return;
-
-	const byte *src = (const byte *)buf;
-
-	// Clip the coordinates
-	if (x < 0) {
-		w += x;
-		src -= x * 2;
-		x = 0;
-	}
-
-	if (y < 0) {
-		h += y;
-		src -= y * pitch;
-		y = 0;
-	}
-
-	if (w > _overlayData.w - x)
-		w = _overlayData.w - x;
-
-	if (h > _overlayData.h - y)
-		h = _overlayData.h - y;
-
-	if (w <= 0 || h <= 0)
-		return;
+void OpenGLGraphicsManager::grabOverlay(void *buf, int pitch) {
+	const Graphics::Surface *overlayData = _overlay->getSurface();
 
-	// Copy buffer data to internal overlay surface
-	byte *dst = (byte *)_overlayData.getBasePtr(0, y);
-	for (int i = 0; i < h; i++) {
-		memcpy(dst + x * _overlayData.format.bytesPerPixel, src, w * _overlayData.format.bytesPerPixel);
-		src += pitch;
-		dst += _overlayData.pitch;
-	}
+	const byte *src = (const byte *)overlayData->getPixels();
+	byte *dst = (byte *)buf;
 
-	// Extend dirty area if not full screen redraw is flagged
-	if (!_overlayNeedsRedraw) {
-		const Common::Rect dirtyRect(x, y, x + w, y + h);
-		_overlayDirtyRect.extend(dirtyRect);
+	for (uint h = overlayData->h; h > 0; --h) {
+		memcpy(dst, src, overlayData->w * overlayData->format.bytesPerPixel);
+		dst += pitch;
+		src += overlayData->pitch;
 	}
 }
 
-int16 OpenGLGraphicsManager::getOverlayHeight() {
-	return _videoMode.overlayHeight;
-}
-
-int16 OpenGLGraphicsManager::getOverlayWidth() {
-	return _videoMode.overlayWidth;
-}
-
-//
-// Cursor
-//
-
 bool OpenGLGraphicsManager::showMouse(bool visible) {
-	if (_cursorVisible == visible)
-		return visible;
-
 	bool last = _cursorVisible;
 	_cursorVisible = visible;
-
 	return last;
 }
 
 void OpenGLGraphicsManager::warpMouse(int x, int y) {
-	int scaledX = x;
-	int scaledY = y;
-
-	int16 currentX = _cursorState.x;
-	int16 currentY = _cursorState.y;
-
+	int16 currentX = _cursorX;
+	int16 currentY = _cursorY;
 	adjustMousePosition(currentX, currentY);
 
-	// Do not adjust the real screen position, when the current game / overlay
-	// coordinates match the requested coordinates. This avoids a slight
-	// movement which might occur otherwise when the mouse is at a subpixel
-	// position.
-	if (x == currentX && y == currentY)
+	// Check whether the (virtual) coordinate actually changed. If not, then
+	// simply do nothing. This avoids ugly "jittering" due to the actual
+	// output screen having a bigger resolution than the virtual coordinates.
+	if (currentX == x && currentY == y) {
 		return;
+	}
 
-	if (_videoMode.mode == OpenGL::GFX_NORMAL) {
-		if (_videoMode.hardwareWidth != _videoMode.overlayWidth)
-			scaledX = scaledX * _videoMode.hardwareWidth / _videoMode.overlayWidth;
-		if (_videoMode.hardwareHeight != _videoMode.overlayHeight)
-			scaledY = scaledY * _videoMode.hardwareHeight / _videoMode.overlayHeight;
-
-		if (!_overlayVisible) {
-			scaledX *= _videoMode.scaleFactor;
-			scaledY *= _videoMode.scaleFactor;
+	// Scale the virtual coordinates into actual physical coordinates.
+	if (_overlayVisible) {
+		if (!_overlay) {
+			return;
 		}
+	
+		// It might be confusing that we actually have to handle something
+		// here when the overlay is visible. This is because for very small
+		// resolutions we have a minimal overlay size and have to adjust
+		// for that.
+		x = (x * _outputScreenWidth)  / _overlay->getWidth();
+		y = (y * _outputScreenHeight) / _overlay->getHeight();
 	} else {
-		if (_overlayVisible) {
-			if (_displayWidth != _videoMode.overlayWidth)
-				scaledX = scaledX * _displayWidth / _videoMode.overlayWidth;
-			if (_displayHeight != _videoMode.overlayHeight)
-				scaledY = scaledY * _displayHeight / _videoMode.overlayHeight;
-		} else {
-			if (_displayWidth != _videoMode.screenWidth)
-				scaledX = scaledX * _displayWidth / _videoMode.screenWidth;
-			if (_displayHeight != _videoMode.screenHeight)
-				scaledY = scaledY * _displayHeight / _videoMode.screenHeight;
+		if (!_gameScreen) {
+			return;
 		}
 
-		scaledX += _displayX;
-		scaledY += _displayY;
+		x = (x * _displayWidth)  / _gameScreen->getWidth();
+		y = (y * _displayHeight) / _gameScreen->getHeight();
+
+		x += _displayX;
+		y += _displayY;
 	}
 
-	setMousePosition(scaledX, scaledY);
-	setInternalMousePosition(scaledX, scaledY);
+	setMousePosition(x, y);
+	setInternalMousePosition(x, y);
+}
+
+namespace {
+template<typename DstPixel, typename SrcPixel>
+void applyColorKey(DstPixel *dst, const SrcPixel *src, uint w, uint h, uint dstPitch, uint srcPitch, SrcPixel keyColor, DstPixel alphaMask) {
+	const uint srcAdd = srcPitch - w * sizeof(SrcPixel);
+	const uint dstAdd = dstPitch - w * sizeof(DstPixel);
+
+	while (h-- > 0) {
+		for (uint x = w; x > 0; --x, ++dst, ++src) {
+			if (*src == keyColor) {
+				*dst &= ~alphaMask;
+			}
+		}
+
+		dst = (DstPixel *)((byte *)dst + dstAdd);
+		src = (const SrcPixel *)((const byte *)src + srcAdd);
+	}
 }
+} // End of anonymous namespace
 
 void OpenGLGraphicsManager::setMouseCursor(const void *buf, uint w, uint h, int hotspotX, int hotspotY, uint32 keycolor, bool dontScale, const Graphics::PixelFormat *format) {
+	Graphics::PixelFormat inputFormat;
 #ifdef USE_RGB_COLOR
-	if (format)
-		_cursorFormat = *format;
-	else
-		_cursorFormat = Graphics::PixelFormat::createFormatCLUT8();
+	if (format) {
+		inputFormat = *format;
+	} else {
+		inputFormat = Graphics::PixelFormat::createFormatCLUT8();
+	}
 #else
-	assert(keycolor <= 255);
-	_cursorFormat = Graphics::PixelFormat::createFormatCLUT8();
+	inputFormat = Graphics::PixelFormat::createFormatCLUT8();
 #endif
 
-	// Allocate space for cursor data
-	if (_cursorData.w != w || _cursorData.h != h ||
-	        _cursorData.format.bytesPerPixel != _cursorFormat.bytesPerPixel)
-		_cursorData.create(w, h, _cursorFormat);
-
-	// Save cursor data
-	memcpy(_cursorData.getPixels(), buf, h * _cursorData.pitch);
+	// In case the color format has changed we will need to create the texture.
+	if (!_cursor || _cursor->getFormat() != inputFormat) {
+		delete _cursor;
+		_cursor = nullptr;
+
+		GLenum glIntFormat, glFormat, glType;
+
+		Graphics::PixelFormat textureFormat;
+		if (inputFormat.bytesPerPixel == 1 || (inputFormat.aBits() && getGLPixelFormat(inputFormat, glIntFormat, glFormat, glType))) {
+			// There is two cases when we can use the cursor format directly.
+			// The first is when it's CLUT8, here color key handling can
+			// always be applied because we use the alpha channel of
+			// _defaultFormatAlpha for that.
+			// The other is when the input format has alpha bits and
+			// furthermore is directly supported.
+			textureFormat = inputFormat;
+		} else {
+			textureFormat = _defaultFormatAlpha;
+		}
+		_cursor = createTexture(textureFormat, true);
+		assert(_cursor);
+		_cursor->enableLinearFiltering(_currentState.graphicsMode == GFX_LINEAR);
+	}
 
-	// Set cursor info
-	_cursorState.w = w;
-	_cursorState.h = h;
-	_cursorState.hotX = hotspotX;
-	_cursorState.hotY = hotspotY;
 	_cursorKeyColor = keycolor;
+	_cursorHotspotX = hotspotX;
+	_cursorHotspotY = hotspotY;
 	_cursorDontScale = dontScale;
-	_cursorNeedsRedraw = true;
 
-	refreshCursorScale();
+	_cursor->allocate(w, h);
+	if (inputFormat.bytesPerPixel == 1) {
+		// For CLUT8 cursors we can simply copy the input data into the
+		// texture.
+		_cursor->copyRectToTexture(0, 0, w, h, buf, w * inputFormat.bytesPerPixel);
+	} else {
+		// Otherwise it is a bit more ugly because we have to handle a key
+		// color properly.
+
+		Graphics::Surface *dst = _cursor->getSurface();
+		const uint srcPitch = w * inputFormat.bytesPerPixel;
+
+		// Copy the cursor data to the actual texture surface. This will make
+		// sure that the data is also converted to the expected format.
+		Graphics::crossBlit((byte *)dst->getPixels(), (const byte *)buf, dst->pitch, srcPitch,
+		                    w, h, dst->format, inputFormat);
+
+		// We apply the color key by setting the alpha bits of the pixels to
+		// fully transparent.
+		const uint32 aMask = (0xFF >> dst->format.aLoss) << dst->format.aShift;
+		if (dst->format.bytesPerPixel == 2) {
+			if (inputFormat.bytesPerPixel == 2) {
+				applyColorKey<uint16, uint16>((uint16 *)dst->getPixels(), (const uint16 *)buf, w, h,
+				                              dst->pitch, srcPitch, keycolor, aMask);
+			} else if (inputFormat.bytesPerPixel == 4) {
+				applyColorKey<uint16, uint32>((uint16 *)dst->getPixels(), (const uint32 *)buf, w, h,
+				                              dst->pitch, srcPitch, keycolor, aMask);
+			}
+		} else {
+			if (inputFormat.bytesPerPixel == 2) {
+				applyColorKey<uint32, uint16>((uint32 *)dst->getPixels(), (const uint16 *)buf, w, h,
+				                              dst->pitch, srcPitch, keycolor, aMask);
+			} else if (inputFormat.bytesPerPixel == 4) {
+				applyColorKey<uint32, uint32>((uint32 *)dst->getPixels(), (const uint32 *)buf, w, h,
+				                              dst->pitch, srcPitch, keycolor, aMask);
+			}
+		}
+
+		// Flag the texture as dirty.
+		_cursor->flagDirty();
+	}
+
+	// In case we actually use a palette set that up properly.
+	if (inputFormat.bytesPerPixel == 1) {
+		updateCursorPalette();
+	}
+
+	// Update the scaling.
+	recalculateCursorScaling();
 }
 
 void OpenGLGraphicsManager::setCursorPalette(const byte *colors, uint start, uint num) {
-	assert(colors);
+	// FIXME: For some reason client code assumes that usage of this function
+	// automatically enables the cursor palette.
+	_cursorPaletteEnabled = true;
 
-	// Save the cursor palette
 	memcpy(_cursorPalette + start * 3, colors, num * 3);
-
-	_cursorPaletteDisabled = false;
-	_cursorNeedsRedraw = true;
+	updateCursorPalette();
 }
 
-//
-// Misc
-//
-
 void OpenGLGraphicsManager::displayMessageOnOSD(const char *msg) {
-	assert(_transactionMode == kTransactionNone);
-	assert(msg);
-
 #ifdef USE_OSD
-	// Split the message into separate lines.
-	_osdLines.clear();
+	// HACK: Actually no client code should use graphics functions from
+	// another thread. But the MT-32 emulator still does, thus we need to
+	// make sure this doesn't happen while a updateScreen call is done.
+	Common::StackLock lock(_osdMutex);
 
+	// Slip up the lines.
+	Common::Array<Common::String> osdLines;
 	Common::StringTokenizer tokenizer(msg, "\n");
-	while (!tokenizer.empty())
-		_osdLines.push_back(tokenizer.nextToken());
+	while (!tokenizer.empty()) {
+		osdLines.push_back(tokenizer.nextToken());
+	}
 
-	// Request update of the texture
-	_requireOSDUpdate = true;
+	// Do the actual drawing like the SDL backend.
+	const Graphics::Font *font = getFontOSD();
+	Graphics::Surface *dst = _osd->getSurface();
+	_osd->fill(0);
+	_osd->flagDirty();
+
+	// Determine a rect which would contain the message string (clipped to the
+	// screen dimensions).
+	const int vOffset = 6;
+	const int lineSpacing = 1;
+	const int lineHeight = font->getFontHeight() + 2 * lineSpacing;
+	int width = 0;
+	int height = lineHeight * osdLines.size() + 2 * vOffset;
+	for (uint i = 0; i < osdLines.size(); i++) {
+		width = MAX(width, font->getStringWidth(osdLines[i]) + 14);
+	}
+
+	// Clip the rect
+	width  = MIN<int>(width,  dst->w);
+	height = MIN<int>(height, dst->h);
+
+	int dstX = (dst->w - width) / 2;
+	int dstY = (dst->h - height) / 2;
+
+	// Draw a dark gray rect.
+	const uint32 color = dst->format.RGBToColor(40, 40, 40);
+	dst->fillRect(Common::Rect(dstX, dstY, dstX + width, dstY + height), color);
+
+	// Render the message, centered, and in white
+	const uint32 white = dst->format.RGBToColor(255, 255, 255);
+	for (uint i = 0; i < osdLines.size(); ++i) {
+		font->drawString(dst, osdLines[i],
+		                 dstX, dstY + i * lineHeight + vOffset + lineSpacing, width,
+		                 white, Graphics::kTextAlignCenter);
+	}
 
-	// Init the OSD display parameters, and the fade out
+	// Init the OSD display parameters.
 	_osdAlpha = kOSDInitialAlpha;
 	_osdFadeStartTime = g_system->getMillis() + kOSDFadeOutDelay;
 #endif
 }
 
-//
-// Intern
-//
+void OpenGLGraphicsManager::setPalette(const byte *colors, uint start, uint num) {
+	assert(_gameScreen->hasPalette());
 
-void OpenGLGraphicsManager::setFullscreenMode(bool enable) {
-	assert(_transactionMode == kTransactionActive);
+	memcpy(_gamePalette + start * 3, colors, num * 3);
+	_gameScreen->setPalette(start, num, colors);
 
-	if (_oldVideoMode.setup && _oldVideoMode.fullscreen == enable)
-		return;
+	// We might need to update the cursor palette here.
+	updateCursorPalette();
+}
 
-	if (_transactionMode == kTransactionActive) {
-		_videoMode.fullscreen = enable;
-		_transactionDetails.needRefresh = true;
-	}
+void OpenGLGraphicsManager::grabPalette(byte *colors, uint start, uint num) {
+	assert(_gameScreen->hasPalette());
+
+	memcpy(colors, _gamePalette + start * 3, num * 3);
 }
 
-void OpenGLGraphicsManager::refreshGameScreen() {
-	if (_screenNeedsRedraw)
-		_screenDirtyRect = Common::Rect(0, 0, _screenData.w, _screenData.h);
-
-	int x = _screenDirtyRect.left;
-	int y = _screenDirtyRect.top;
-	int w = _screenDirtyRect.width();
-	int h = _screenDirtyRect.height();
-
-	if (_screenData.format.bytesPerPixel == 1) {
-		// Create a temporary RGB888 surface
-		byte *surface = new byte[w * h * 3];
-
-		// Convert the paletted buffer to RGB888
-		const byte *src = (byte *)_screenData.getBasePtr(0, y);
-		src += x * _screenData.format.bytesPerPixel;
-		byte *dst = surface;
-		for (int i = 0; i < h; i++) {
-			for (int j = 0; j < w; j++) {
-				dst[0] = _gamePalette[src[j] * 3];
-				dst[1] = _gamePalette[src[j] * 3 + 1];
-				dst[2] = _gamePalette[src[j] * 3 + 2];
-				dst += 3;
-			}
-			src += _screenData.pitch;
+void OpenGLGraphicsManager::setActualScreenSize(uint width, uint height) {
+	_outputScreenWidth = width;
+	_outputScreenHeight = height;
+
+	// Setup coordinates system.
+	GLCALL(glViewport(0, 0, _outputScreenWidth, _outputScreenHeight));
+
+	GLCALL(glMatrixMode(GL_PROJECTION));
+	GLCALL(glLoadIdentity());
+#ifdef USE_GLES
+	GLCALL(glOrthof(0, _outputScreenWidth, _outputScreenHeight, 0, -1, 1));
+#else
+	GLCALL(glOrtho(0, _outputScreenWidth, _outputScreenHeight, 0, -1, 1));
+#endif
+	GLCALL(glMatrixMode(GL_MODELVIEW));
+	GLCALL(glLoadIdentity());
+
+	uint overlayWidth = width;
+	uint overlayHeight = height;
+
+	// WORKAROUND: We can only support surfaces up to the maximum supported
+	// texture size. Thus, in case we encounter a physical size bigger than
+	// this maximum texture size we will simply use an overlay as big as
+	// possible and then scale it to the physical display size. This sounds
+	// bad but actually all recent chips should support full HD resolution
+	// anyway. Thus, it should not be a real issue for modern hardware.
+	if (   overlayWidth  > (uint)Texture::getMaximumTextureSize()
+	    || overlayHeight > (uint)Texture::getMaximumTextureSize()) {
+		const frac_t outputAspect = intToFrac(_outputScreenWidth) / _outputScreenHeight;
+
+		if (outputAspect > (frac_t)FRAC_ONE) {
+			overlayWidth  = Texture::getMaximumTextureSize();
+			overlayHeight = intToFrac(overlayWidth) / outputAspect;
+		} else {
+			overlayHeight = Texture::getMaximumTextureSize();
+			overlayWidth  = fracToInt(overlayHeight * outputAspect);
 		}
+	}
 
-		// Update the texture
-		_gameTexture->updateBuffer(surface, w * 3, x, y, w, h);
+	// HACK: We limit the minimal overlay size to 256x200, which is the
+	// minimum of the dimensions of the two resolutions 256x240 (NES) and
+	// 320x200 (many DOS games use this). This hopefully assure that our
+	// GUI has working layouts.
+	overlayWidth = MAX<uint>(overlayWidth, 256);
+	overlayHeight = MAX<uint>(overlayHeight, 200);
+
+	if (!_overlay || _overlay->getFormat() != _defaultFormatAlpha) {
+		delete _overlay;
+		_overlay = nullptr;
+
+		_overlay = createTexture(_defaultFormatAlpha);
+		assert(_overlay);
+		// We always filter the overlay with GL_LINEAR. This assures it's
+		// readable in case it needs to be scaled and does not affect it
+		// otherwise.
+		_overlay->enableLinearFiltering(true);
+	}
+	_overlay->allocate(overlayWidth, overlayHeight);
+	_overlay->fill(0);
 
-		// Free the temp surface
-		delete[] surface;
-	} else {
-		// Update the texture
-		_gameTexture->updateBuffer((byte *)_screenData.getBasePtr(x, y), _screenData.pitch, x, y, w, h);
+#ifdef USE_OSD
+	if (!_osd || _osd->getFormat() != _defaultFormatAlpha) {
+		delete _osd;
+		_osd = nullptr;
+
+		_osd = createTexture(_defaultFormatAlpha);
+		assert(_osd);
+		// We always filter the osd with GL_LINEAR. This assures it's
+		// readable in case it needs to be scaled and does not affect it
+		// otherwise.
+		_osd->enableLinearFiltering(true);
 	}
+	_osd->allocate(_overlay->getWidth(), _overlay->getHeight());
+	_osd->fill(0);
+#endif
 
-	_screenNeedsRedraw = false;
-	_screenDirtyRect = Common::Rect();
+	// Re-setup the scaling for the screen and cursor
+	recalculateDisplayArea();
+	recalculateCursorScaling();
+
+	// Something changed, so update the screen change ID.
+	++_screenChangeID;
 }
 
-void OpenGLGraphicsManager::refreshOverlay() {
-	if (_overlayNeedsRedraw)
-		_overlayDirtyRect = Common::Rect(0, 0, _overlayData.w, _overlayData.h);
-
-	int x = _overlayDirtyRect.left;
-	int y = _overlayDirtyRect.top;
-	int w = _overlayDirtyRect.width();
-	int h = _overlayDirtyRect.height();
-
-	if (_overlayData.format.bytesPerPixel == 1) {
-		// Create a temporary RGB888 surface
-		byte *surface = new byte[w * h * 3];
-
-		// Convert the paletted buffer to RGB888
-		const byte *src = (byte *)_overlayData.getBasePtr(0, y);
-		src += x * _overlayData.format.bytesPerPixel;
-		byte *dst = surface;
-		for (int i = 0; i < h; i++) {
-			for (int j = 0; j < w; j++) {
-				dst[0] = _gamePalette[src[j] * 3];
-				dst[1] = _gamePalette[src[j] * 3 + 1];
-				dst[2] = _gamePalette[src[j] * 3 + 2];
-				dst += 3;
-			}
-			src += _screenData.pitch;
-		}
+void OpenGLGraphicsManager::notifyContextCreate(const Graphics::PixelFormat &defaultFormat, const Graphics::PixelFormat &defaultFormatAlpha) {
+	// Initialize all extensions.
+	initializeGLExtensions();
 
-		// Update the texture
-		_overlayTexture->updateBuffer(surface, w * 3, x, y, w, h);
+	// Disable 3D properties.
+	GLCALL(glDisable(GL_CULL_FACE));
+	GLCALL(glDisable(GL_DEPTH_TEST));
+	GLCALL(glDisable(GL_LIGHTING));
+	GLCALL(glDisable(GL_FOG));
+	GLCALL(glDisable(GL_DITHER));
+	GLCALL(glShadeModel(GL_FLAT));
+	GLCALL(glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_FASTEST));
 
-		// Free the temp surface
-		delete[] surface;
-	} else {
-		// Update the texture
-		_overlayTexture->updateBuffer((byte *)_overlayData.getBasePtr(x, y), _overlayData.pitch, x, y, w, h);
+	// Default to black as clear color.
+	GLCALL(glClearColor(0.0f, 0.0f, 0.0f, 0.0f));
+	GLCALL(glColor4f(1.0f, 1.0f, 1.0f, 1.0f));
+
+	// Setup alpha blend (for overlay and cursor).
+	GLCALL(glEnable(GL_BLEND));
+	GLCALL(glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA));
+
+	// Enable rendering with vertex and coord arrays.
+	GLCALL(glEnableClientState(GL_VERTEX_ARRAY));
+	GLCALL(glEnableClientState(GL_TEXTURE_COORD_ARRAY));
+
+	GLCALL(glEnable(GL_TEXTURE_2D));
+
+	// We use a "pack" alignment (when reading from textures) to 4 here,
+	// since the only place where we really use it is the BMP screenshot
+	// code and that requires the same alignment too.
+	GLCALL(glPixelStorei(GL_PACK_ALIGNMENT, 4));
+
+	// Query information needed by textures.
+	Texture::queryTextureInformation();
+
+	// Refresh the output screen dimensions if some are set up.
+	if (_outputScreenWidth != 0 && _outputScreenHeight != 0) {
+		setActualScreenSize(_outputScreenWidth, _outputScreenHeight);
 	}
 
-	_overlayNeedsRedraw = false;
-	_overlayDirtyRect = Common::Rect();
-}
+	// TODO: Should we try to convert textures into one of those formats if
+	// possible? For example, when _gameScreen is CLUT8 we might want to use
+	// defaultFormat now.
+	_defaultFormat = defaultFormat;
+	_defaultFormatAlpha = defaultFormatAlpha;
 
-void OpenGLGraphicsManager::refreshCursor() {
-	_cursorNeedsRedraw = false;
-
-	// Allocate a texture big enough for cursor
-	_cursorTexture->allocBuffer(_cursorState.w, _cursorState.h);
-
-	// Create a temporary RGBA8888 surface
-	byte *surface = new byte[_cursorState.w * _cursorState.h * 4];
-	memset(surface, 0, _cursorState.w * _cursorState.h * 4);
-
-	byte *dst = surface;
-
-	// Convert the paletted cursor to RGBA8888
-	if (_cursorFormat.bytesPerPixel == 1) {
-		// Select palette
-		byte *palette;
-		if (_cursorPaletteDisabled)
-			palette = _gamePalette;
-		else
-			palette = _cursorPalette;
-
-		// Convert the paletted cursor to RGBA8888
-		const byte *src = (byte *)_cursorData.getPixels();
-		for (int i = 0; i < _cursorState.w * _cursorState.h; i++) {
-			// Check for keycolor
-			if (src[i] != _cursorKeyColor) {
-				dst[0] = palette[src[i] * 3];
-				dst[1] = palette[src[i] * 3 + 1];
-				dst[2] = palette[src[i] * 3 + 2];
-				dst[3] = 255;
-			}
-			dst += 4;
-		}
-	} else {
-		const bool gotNoAlpha = (_cursorFormat.aLoss == 8);
-
-		// Convert the RGB cursor to RGBA8888
-		if (_cursorFormat.bytesPerPixel == 2) {
-			const uint16 *src = (uint16 *)_cursorData.getPixels();
-			for (int i = 0; i < _cursorState.w * _cursorState.h; i++) {
-				// Check for keycolor
-				if (src[i] != _cursorKeyColor) {
-					_cursorFormat.colorToARGB(src[i], dst[3], dst[0], dst[1], dst[2]);
-
-					if (gotNoAlpha)
-						dst[3] = 255;
-				}
-				dst += 4;
-			}
-		} else if (_cursorFormat.bytesPerPixel == 4) {
-			const uint32 *src = (uint32 *)_cursorData.getPixels();
-			for (int i = 0; i < _cursorState.w * _cursorState.h; i++) {
-				// Check for keycolor
-				if (src[i] != _cursorKeyColor) {
-					_cursorFormat.colorToARGB(src[i], dst[3], dst[0], dst[1], dst[2]);
-
-					if (gotNoAlpha)
-						dst[3] = 255;
-				}
-				dst += 4;
-			}
-		}
+	if (_gameScreen) {
+		_gameScreen->recreateInternalTexture();
 	}
 
-	// Update the texture with new cursor
-	_cursorTexture->updateBuffer(surface, _cursorState.w * 4, 0, 0, _cursorState.w, _cursorState.h);
+	if (_overlay) {
+		_overlay->recreateInternalTexture();
+	}
+
+	if (_cursor) {
+		_cursor->recreateInternalTexture();
+	}
 
-	// Free the temp surface
-	delete[] surface;
+#ifdef USE_OSD
+	if (_osd) {
+		_osd->recreateInternalTexture();
+	}
+#endif
 }
 
-void OpenGLGraphicsManager::refreshCursorScale() {
-	// Calculate the scale factors of the screen.
-	// We also totally ignore the aspect of the overlay cursor, since aspect
-	// ratio correction only applies to the game screen.
-	// TODO: It might make sense to always ignore scaling of the mouse cursor
-	// when the overlay is visible.
-	uint screenScaleFactorX = _videoMode.hardwareWidth * 10000 / _videoMode.screenWidth;
-	uint screenScaleFactorY = _videoMode.hardwareHeight * 10000 / _videoMode.screenHeight;
-
-	// Ignore scaling when the cursor should not be scaled.
-	if (_cursorDontScale) {
-		screenScaleFactorX = 10000;
-		screenScaleFactorY = 10000;
+void OpenGLGraphicsManager::notifyContextDestroy() {
+	if (_gameScreen) {
+		_gameScreen->releaseInternalTexture();
 	}
 
-	// Apply them (without any possible) aspect ratio correction to the
-	// overlay.
-	_cursorState.rW = (int16)(_cursorState.w * screenScaleFactorX / 10000);
-	_cursorState.rH = (int16)(_cursorState.h * screenScaleFactorY / 10000);
-	_cursorState.rHotX = (int16)(_cursorState.hotX * screenScaleFactorX / 10000);
-	_cursorState.rHotY = (int16)(_cursorState.hotY * screenScaleFactorY / 10000);
-
-	// Only apply scaling when it's desired.
-	if (_cursorDontScale) {
-		screenScaleFactorX = 10000;
-		screenScaleFactorY = 10000;
-	} else {
-		// Make sure we properly scale the cursor according to the desired aspect.
-		int width, height;
-		calculateDisplaySize(width, height);
-		screenScaleFactorX = (width * 10000 / _videoMode.screenWidth);
-		screenScaleFactorY = (height * 10000 / _videoMode.screenHeight);
+	if (_overlay) {
+		_overlay->releaseInternalTexture();
 	}
 
-	// Apply the scale cursor scaling for the game screen.
-	_cursorState.vW = (int16)(_cursorState.w * screenScaleFactorX / 10000);
-	_cursorState.vH = (int16)(_cursorState.h * screenScaleFactorY / 10000);
-	_cursorState.vHotX = (int16)(_cursorState.hotX * screenScaleFactorX / 10000);
-	_cursorState.vHotY = (int16)(_cursorState.hotY * screenScaleFactorY / 10000);
+	if (_cursor) {
+		_cursor->releaseInternalTexture();
+	}
+
+#ifdef USE_OSD
+	if (_osd) {
+		_osd->releaseInternalTexture();
+	}
+#endif
 }
 
-void OpenGLGraphicsManager::calculateDisplaySize(int &width, int &height) {
-	if (_videoMode.mode == OpenGL::GFX_ORIGINAL) {
-		width = _videoMode.screenWidth;
-		height = _videoMode.screenHeight;
-	} else {
-		width = _videoMode.hardwareWidth;
-		height = _videoMode.hardwareHeight;
+void OpenGLGraphicsManager::adjustMousePosition(int16 &x, int16 &y) {
+	if (_overlayVisible) {
+		// It might be confusing that we actually have to handle something
+		// here when the overlay is visible. This is because for very small
+		// resolutions we have a minimal overlay size and have to adjust
+		// for that.
+		// This can also happen when the overlay is smaller than the actual
+		// display size because of texture size limitations.
+		if (_overlay) {
+			x = (x * _overlay->getWidth())  / _outputScreenWidth;
+			y = (y * _overlay->getHeight()) / _outputScreenHeight;
+		}
+	} else if (_gameScreen) {
+		x -= _displayX;
+		y -= _displayY;
+
+		const int16 width  = _gameScreen->getWidth();
+		const int16 height = _gameScreen->getHeight();
 
-		uint aspectRatio = (_videoMode.hardwareWidth * 10000 + 5000) / _videoMode.hardwareHeight;
-		uint desiredAspectRatio = getAspectRatio();
+		x = (x * width)  / _displayWidth;
+		y = (y * height) / _displayHeight;
 
-		// Adjust one screen dimension for mantaining the aspect ratio
-		if (aspectRatio < desiredAspectRatio)
-			height = (width * 10000 + 5000) / desiredAspectRatio;
-		else if (aspectRatio > desiredAspectRatio)
-			width = (height * desiredAspectRatio + 5000) / 10000;
+		// Make sure we only supply valid coordinates.
+		x = CLIP<int16>(x, 0, width - 1);
+		y = CLIP<int16>(y, 0, height - 1);
 	}
 }
 
-void OpenGLGraphicsManager::refreshDisplaySize() {
-	calculateDisplaySize(_displayWidth, _displayHeight);
-
-	// Adjust x and y for centering the screen
-	_displayX = (_videoMode.hardwareWidth - _displayWidth) / 2;
-	_displayY = (_videoMode.hardwareHeight - _displayHeight) / 2;
+Texture *OpenGLGraphicsManager::createTexture(const Graphics::PixelFormat &format, bool wantAlpha) {
+	GLenum glIntFormat, glFormat, glType;
+	if (format.bytesPerPixel == 1) {
+		const Graphics::PixelFormat &virtFormat = wantAlpha ? _defaultFormatAlpha : _defaultFormat;
+		const bool supported = getGLPixelFormat(virtFormat, glIntFormat, glFormat, glType);
+		if (!supported) {
+			return nullptr;
+		} else {
+			return new TextureCLUT8(glIntFormat, glFormat, glType, virtFormat);
+		}
+	} else {
+		const bool supported = getGLPixelFormat(format, glIntFormat, glFormat, glType);
+		if (!supported) {
+			return nullptr;
+		} else {
+			return new Texture(glIntFormat, glFormat, glType, format);
+		}
+	}
 }
 
-void OpenGLGraphicsManager::getGLPixelFormat(Graphics::PixelFormat pixelFormat, byte &bpp, GLenum &intFormat, GLenum &glFormat, GLenum &gltype) {
+bool OpenGLGraphicsManager::getGLPixelFormat(const Graphics::PixelFormat &pixelFormat, GLenum &glIntFormat, GLenum &glFormat, GLenum &glType) const {
+#ifdef SCUMM_LITTLE_ENDIAN
+	if (pixelFormat == Graphics::PixelFormat(4, 8, 8, 8, 8, 0, 8, 16, 24)) { // ABGR8888
+#else
 	if (pixelFormat == Graphics::PixelFormat(4, 8, 8, 8, 8, 24, 16, 8, 0)) { // RGBA8888
-		bpp = 4;
-		intFormat = GL_RGBA;
+#endif
+		glIntFormat = GL_RGBA;
 		glFormat = GL_RGBA;
-		gltype = GL_UNSIGNED_INT_8_8_8_8;
-	} else if (pixelFormat == Graphics::PixelFormat(3, 8, 8, 8, 0, 16, 8, 0, 0)) { // RGB888
-		bpp = 3;
-		intFormat = GL_RGB;
-		glFormat = GL_RGB;
-		gltype = GL_UNSIGNED_BYTE;
+		glType = GL_UNSIGNED_BYTE;
+		return true;
 	} else if (pixelFormat == Graphics::PixelFormat(2, 5, 6, 5, 0, 11, 5, 0, 0)) { // RGB565
-		bpp = 2;
-		intFormat = GL_RGB;
+		glIntFormat = GL_RGB;
 		glFormat = GL_RGB;
-		gltype = GL_UNSIGNED_SHORT_5_6_5;
-	} else if (pixelFormat == Graphics::PixelFormat(2, 5, 5, 5, 1, 11, 6, 1, 0)) { // RGB5551
-		bpp = 2;
-		intFormat = GL_RGBA;
+		glType = GL_UNSIGNED_SHORT_5_6_5;
+		return true;
+	} else if (pixelFormat == Graphics::PixelFormat(2, 5, 5, 5, 1, 11, 6, 1, 0)) { // RGBA5551
+		glIntFormat = GL_RGBA;
 		glFormat = GL_RGBA;
-		gltype = GL_UNSIGNED_SHORT_5_5_5_1;
+		glType = GL_UNSIGNED_SHORT_5_5_5_1;
+		return true;
 	} else if (pixelFormat == Graphics::PixelFormat(2, 4, 4, 4, 4, 12, 8, 4, 0)) { // RGBA4444
-		bpp = 2;
-		intFormat = GL_RGBA;
+		glIntFormat = GL_RGBA;
 		glFormat = GL_RGBA;
-		gltype = GL_UNSIGNED_SHORT_4_4_4_4;
-	} else if (pixelFormat.bytesPerPixel == 1) { // CLUT8
-		// If uses a palette, create texture as RGB888. The pixel data will be converted
-		// later.
-		bpp = 3;
-		intFormat = GL_RGB;
-		glFormat = GL_RGB;
-		gltype = GL_UNSIGNED_BYTE;
+		glType = GL_UNSIGNED_SHORT_4_4_4_4;
+		return true;
 #ifndef USE_GLES
+#ifdef SCUMM_LITTLE_ENDIAN
+	} else if (pixelFormat == Graphics::PixelFormat(4, 8, 8, 8, 8, 24, 16, 8, 0)) { // RGBA8888
+		glIntFormat = GL_RGBA;
+		glFormat = GL_RGBA;
+		glType = GL_UNSIGNED_INT_8_8_8_8;
+		return true;
+#endif
 	} else if (pixelFormat == Graphics::PixelFormat(2, 5, 5, 5, 0, 10, 5, 0, 0)) { // RGB555
 		// GL_BGRA does not exist in every GLES implementation so should not be configured if
 		// USE_GLES is set.
-		bpp = 2;
-		intFormat = GL_RGB;
+		glIntFormat = GL_RGB;
 		glFormat = GL_BGRA;
-		gltype = GL_UNSIGNED_SHORT_1_5_5_5_REV;
+		glType = GL_UNSIGNED_SHORT_1_5_5_5_REV;
+		return true;
 	} else if (pixelFormat == Graphics::PixelFormat(4, 8, 8, 8, 8, 16, 8, 0, 24)) { // ARGB8888
-		bpp = 4;
-		intFormat = GL_RGBA;
+		glIntFormat = GL_RGBA;
 		glFormat = GL_BGRA;
-		gltype = GL_UNSIGNED_INT_8_8_8_8_REV;
+		glType = GL_UNSIGNED_INT_8_8_8_8_REV;
+		return true;
 	} else if (pixelFormat == Graphics::PixelFormat(2, 4, 4, 4, 4, 8, 4, 0, 12)) { // ARGB4444
-		bpp = 2;
-		intFormat = GL_RGBA;
+		glIntFormat = GL_RGBA;
 		glFormat = GL_BGRA;
-		gltype = GL_UNSIGNED_SHORT_4_4_4_4_REV;
+		glType = GL_UNSIGNED_SHORT_4_4_4_4_REV;
+		return true;
+#ifdef SCUMM_BIG_ENDIAN
 	} else if (pixelFormat == Graphics::PixelFormat(4, 8, 8, 8, 8, 0, 8, 16, 24)) { // ABGR8888
-		bpp = 4;
-		intFormat = GL_RGBA;
+		glIntFormat = GL_RGBA;
 		glFormat = GL_RGBA;
-		gltype = GL_UNSIGNED_INT_8_8_8_8_REV;
+		glType = GL_UNSIGNED_INT_8_8_8_8_REV;
+		return true;
+#endif
 	} else if (pixelFormat == Graphics::PixelFormat(4, 8, 8, 8, 8, 8, 16, 24, 0)) { // BGRA8888
-		bpp = 4;
-		intFormat = GL_RGBA;
+		glIntFormat = GL_RGBA;
 		glFormat = GL_BGRA;
-		gltype = GL_UNSIGNED_BYTE;
-	} else if (pixelFormat == Graphics::PixelFormat(3, 8, 8, 8, 0, 0, 8, 16, 0)) { // BGR888
-		bpp = 3;
-		intFormat = GL_RGB;
-		glFormat = GL_BGR;
-		gltype = GL_UNSIGNED_BYTE;
+		glType = GL_UNSIGNED_INT_8_8_8_8;
+		return true;
 	} else if (pixelFormat == Graphics::PixelFormat(2, 5, 6, 5, 0, 0, 5, 11, 0)) { // BGR565
-		bpp = 2;
-		intFormat = GL_RGB;
+		glIntFormat = GL_RGB;
 		glFormat = GL_BGR;
-		gltype = GL_UNSIGNED_SHORT_5_6_5;
+		glType = GL_UNSIGNED_SHORT_5_6_5;
+		return true;
 	} else if (pixelFormat == Graphics::PixelFormat(2, 5, 5, 5, 1, 1, 6, 11, 0)) { // BGRA5551
-		bpp = 2;
-		intFormat = GL_RGBA;
+		glIntFormat = GL_RGBA;
 		glFormat = GL_BGRA;
-		gltype = GL_UNSIGNED_SHORT_5_5_5_1;
+		glType = GL_UNSIGNED_SHORT_5_5_5_1;
+		return true;
 	} else if (pixelFormat == Graphics::PixelFormat(2, 4, 4, 4, 4, 0, 4, 8, 12)) { // ABGR4444
-		bpp = 2;
-		intFormat = GL_RGBA;
+		glIntFormat = GL_RGBA;
 		glFormat = GL_RGBA;
-		gltype = GL_UNSIGNED_SHORT_4_4_4_4_REV;
+		glType = GL_UNSIGNED_SHORT_4_4_4_4_REV;
+		return true;
 	} else if (pixelFormat == Graphics::PixelFormat(2, 4, 4, 4, 4, 4, 8, 12, 0)) { // BGRA4444
-		bpp = 2;
-		intFormat = GL_RGBA;
+		glIntFormat = GL_RGBA;
 		glFormat = GL_BGRA;
-		gltype = GL_UNSIGNED_SHORT_4_4_4_4;
+		glType = GL_UNSIGNED_SHORT_4_4_4_4;
+		return true;
 #endif
 	} else {
-		error("OpenGLGraphicsManager: Pixel format not supported");
+		return false;
 	}
 }
 
-void OpenGLGraphicsManager::internUpdateScreen() {
-	// Clear the screen buffer
-	glClear(GL_COLOR_BUFFER_BIT); CHECK_GL_ERROR();
-
-	if (_screenNeedsRedraw || !_screenDirtyRect.isEmpty())
-		// Refresh texture if dirty
-		refreshGameScreen();
-
-	int scaleFactor = _videoMode.hardwareHeight / _videoMode.screenHeight;
-
-	glPushMatrix();
-
-	// Adjust game screen shake position
-	glTranslatef(0, _shakePos * scaleFactor, 0); CHECK_GL_ERROR();
-
-	// Draw the game screen
-	_gameTexture->drawTexture(_displayX, _displayY, _displayWidth, _displayHeight);
-
-	glPopMatrix();
-
-	if (_overlayVisible) {
-		if (_overlayNeedsRedraw || !_overlayDirtyRect.isEmpty())
-			// Refresh texture if dirty
-			refreshOverlay();
-
-		// Draw the overlay
-		_overlayTexture->drawTexture(0, 0, _videoMode.overlayWidth, _videoMode.overlayHeight);
-	}
-
-	if (_cursorVisible) {
-		if (_cursorNeedsRedraw)
-			// Refresh texture if dirty
-			refreshCursor();
+frac_t OpenGLGraphicsManager::getDesiredGameScreenAspect() const {
+	const uint width  = _currentState.gameWidth;
+	const uint height = _currentState.gameHeight;
 
-		glPushMatrix();
-
-		// Adjust mouse shake position, unless the overlay is visible
-		glTranslatef(0, _overlayVisible ? 0 : _shakePos * scaleFactor, 0); CHECK_GL_ERROR();
-
-		// Draw the cursor
-		if (_overlayVisible)
-			_cursorTexture->drawTexture(_cursorState.x - _cursorState.rHotX,
-			                            _cursorState.y - _cursorState.rHotY, _cursorState.rW, _cursorState.rH);
-		else
-			_cursorTexture->drawTexture(_cursorState.x - _cursorState.vHotX,
-			                            _cursorState.y - _cursorState.vHotY, _cursorState.vW, _cursorState.vH);
-
-		glPopMatrix();
-	}
-
-#ifdef USE_OSD
-	if (_osdAlpha > 0) {
-		if (_requireOSDUpdate) {
-			updateOSD();
-			_requireOSDUpdate = false;
-		}
-
-		// Update alpha value
-		const int diff = g_system->getMillis() - _osdFadeStartTime;
-		if (diff > 0) {
-			if (diff >= kOSDFadeOutDuration) {
-				// Back to full transparency
-				_osdAlpha = 0;
-			} else {
-				// Do a fade out
-				_osdAlpha = kOSDInitialAlpha - diff * kOSDInitialAlpha / kOSDFadeOutDuration;
-			}
+	if (_currentState.aspectRatioCorrection) {
+		// In case we enable aspect ratio correction we force a 4/3 ratio.
+		// But just for 320x200 and 640x400 games, since other games do not need
+		// this.
+		if ((width == 320 && height == 200) || (width == 640 && height == 400)) {
+			return intToFrac(4) / 3;
 		}
-		// Set the osd transparency
-		glColor4f(1.0f, 1.0f, 1.0f, _osdAlpha / 100.0f); CHECK_GL_ERROR();
-
-		// Draw the osd texture
-		_osdTexture->drawTexture(0, 0, _videoMode.hardwareWidth, _videoMode.hardwareHeight);
-
-		// Reset color
-		glColor4f(1.0f, 1.0f, 1.0f, 1.0f); CHECK_GL_ERROR();
 	}
-#endif
-}
-
-void OpenGLGraphicsManager::initGL() {
-	// Check available GL Extensions
-	GLTexture::initGLExtensions();
-
-	// Disable 3D properties
-	glDisable(GL_CULL_FACE); CHECK_GL_ERROR();
-	glDisable(GL_DEPTH_TEST); CHECK_GL_ERROR();
-	glDisable(GL_LIGHTING); CHECK_GL_ERROR();
-	glDisable(GL_FOG); CHECK_GL_ERROR();
-	glDisable(GL_DITHER); CHECK_GL_ERROR();
-	glShadeModel(GL_FLAT); CHECK_GL_ERROR();
-	glHint(GL_PERSPECTIVE_CORRECTION_HINT, GL_FASTEST); CHECK_GL_ERROR();
-
-	// Setup alpha blend (For overlay and cursor)
-	glEnable(GL_BLEND); CHECK_GL_ERROR();
-	glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA); CHECK_GL_ERROR();
-
-	// Enable rendering with vertex and coord arrays
-	glEnableClientState(GL_VERTEX_ARRAY); CHECK_GL_ERROR();
-	glEnableClientState(GL_TEXTURE_COORD_ARRAY); CHECK_GL_ERROR();
 
-	glEnable(GL_TEXTURE_2D); CHECK_GL_ERROR();
-
-	// Setup the GL viewport
-	glViewport(0, 0, _videoMode.hardwareWidth, _videoMode.hardwareHeight); CHECK_GL_ERROR();
-
-	// Setup coordinates system
-	glMatrixMode(GL_PROJECTION); CHECK_GL_ERROR();
-	glLoadIdentity(); CHECK_GL_ERROR();
-#ifdef USE_GLES
-	glOrthof(0, _videoMode.hardwareWidth, _videoMode.hardwareHeight, 0, -1, 1); CHECK_GL_ERROR();
-#else
-	glOrtho(0, _videoMode.hardwareWidth, _videoMode.hardwareHeight, 0, -1, 1); CHECK_GL_ERROR();
-#endif
-	glMatrixMode(GL_MODELVIEW); CHECK_GL_ERROR();
-	glLoadIdentity(); CHECK_GL_ERROR();
+	return intToFrac(width) / height;
 }
 
-void OpenGLGraphicsManager::loadTextures() {
-#ifdef USE_RGB_COLOR
-	if (_transactionDetails.formatChanged && _gameTexture) {
-		delete _gameTexture;
-		_gameTexture = 0;
+void OpenGLGraphicsManager::recalculateDisplayArea() {
+	if (!_gameScreen || _outputScreenHeight == 0) {
+		return;
 	}
-#endif
 
-	if (!_gameTexture) {
-		byte bpp;
-		GLenum intformat;
-		GLenum format;
-		GLenum type;
-#ifdef USE_RGB_COLOR
-		getGLPixelFormat(_screenFormat, bpp, intformat, format, type);
-#else
-		getGLPixelFormat(Graphics::PixelFormat::createFormatCLUT8(), bpp, intformat, format, type);
-#endif
-		_gameTexture = new GLTexture(bpp, intformat, format, type);
-	} else
-		_gameTexture->refresh();
-
-	_overlayFormat = Graphics::PixelFormat(2, 5, 5, 5, 1, 11, 6, 1, 0);
-
-	if (!_overlayTexture) {
-		byte bpp;
-		GLenum intformat;
-		GLenum format;
-		GLenum type;
-		getGLPixelFormat(_overlayFormat, bpp, intformat, format, type);
-		_overlayTexture = new GLTexture(bpp, intformat, format, type);
-	} else
-		_overlayTexture->refresh();
-
-	if (!_cursorTexture)
-		_cursorTexture = new GLTexture(4, GL_RGBA, GL_RGBA, GL_UNSIGNED_BYTE);
-	else
-		_cursorTexture->refresh();
-
-	GLint filter = _videoMode.antialiasing ? GL_LINEAR : GL_NEAREST;
-	_gameTexture->setFilter(filter);
-	_overlayTexture->setFilter(filter);
-	_cursorTexture->setFilter(filter);
-
-	// Allocate texture memory and finish refreshing
-	_gameTexture->allocBuffer(_videoMode.screenWidth, _videoMode.screenHeight);
-	_overlayTexture->allocBuffer(_videoMode.overlayWidth, _videoMode.overlayHeight);
-	_cursorTexture->allocBuffer(_cursorState.w, _cursorState.h);
-
-	if (
-#ifdef USE_RGB_COLOR
-	    _transactionDetails.formatChanged ||
-#endif
-	    _oldVideoMode.screenWidth != _videoMode.screenWidth ||
-	    _oldVideoMode.screenHeight != _videoMode.screenHeight)
-		_screenData.create(_videoMode.screenWidth, _videoMode.screenHeight,
-#ifdef USE_RGB_COLOR
-		                   _screenFormat
-#else
-		                   Graphics::PixelFormat::createFormatCLUT8()
-#endif
-		                  );
-
-
-	if (_oldVideoMode.overlayWidth != _videoMode.overlayWidth ||
-	        _oldVideoMode.overlayHeight != _videoMode.overlayHeight)
-		_overlayData.create(_videoMode.overlayWidth, _videoMode.overlayHeight,
-		                    _overlayFormat);
+	const frac_t outputAspect = intToFrac(_outputScreenWidth) / _outputScreenHeight;
+	const frac_t desiredAspect = getDesiredGameScreenAspect();
 
-	_screenNeedsRedraw = true;
-	_overlayNeedsRedraw = true;
-	_cursorNeedsRedraw = true;
+	_displayWidth = _outputScreenWidth;
+	_displayHeight = _outputScreenHeight;
 
-	// We need to setup a proper unpack alignment value here, else we will
-	// get problems with the texture updates, in case the surface data is
-	// not properly aligned.
-	// It is noteworthy this assumes the OSD uses the same BPP as the overlay
-	// and that the cursor works with any alignment setting.
-	int newAlignment = Common::gcd(_gameTexture->getBytesPerPixel(), _overlayTexture->getBytesPerPixel());
-	assert(newAlignment == 1 || newAlignment == 2 || newAlignment == 4);
-	glPixelStorei(GL_UNPACK_ALIGNMENT, newAlignment);
-
-	// We use a "pack" alignment (when reading from textures) to 4 here,
-	// since the only place where we really use it is the BMP screenshot
-	// code and that requires the same alignment too.
-	glPixelStorei(GL_PACK_ALIGNMENT, 4);
-
-#ifdef USE_OSD
-	if (!_osdTexture)
-		_osdTexture = new GLTexture(2, GL_RGBA, GL_RGBA, GL_UNSIGNED_SHORT_5_5_5_1);
-	else
-		_osdTexture->refresh();
-
-	_osdTexture->allocBuffer(_videoMode.overlayWidth, _videoMode.overlayHeight);
+	// Adjust one dimension for mantaining the aspect ratio.
+	if (outputAspect < desiredAspect) {
+		_displayHeight = intToFrac(_displayWidth) / desiredAspect;
+	} else if (outputAspect > desiredAspect) {
+		_displayWidth = fracToInt(_displayHeight * desiredAspect);
+	}
 
-	// Update the OSD in case it is used right now
-	_requireOSDUpdate = true;
-#endif
+	// We center the screen in the middle for now.
+	_displayX = (_outputScreenWidth  - _displayWidth ) / 2; 
+	_displayY = (_outputScreenHeight - _displayHeight) / 2; 
 }
 
-bool OpenGLGraphicsManager::loadGFXMode() {
-	// Initialize OpenGL settings
-	initGL();
-
-	loadTextures();
-
-	refreshCursorScale();
-
-	refreshDisplaySize();
-
-	internUpdateScreen();
-
-	return true;
-}
+void OpenGLGraphicsManager::updateCursorPalette() {
+	if (!_cursor || !_cursor->hasPalette()) {
+		return;
+	}
 
-void OpenGLGraphicsManager::unloadGFXMode() {
+	if (_cursorPaletteEnabled) {
+		_cursor->setPalette(0, 256, _cursorPalette);
+	} else {
+		_cursor->setPalette(0, 256, _gamePalette);
+	}
 
+	// We remove all alpha bits from the palette entry of the color key.
+	// This makes sure its properly handled as color key.
+	const Graphics::PixelFormat &hardwareFormat = _cursor->getHardwareFormat();
+	const uint32 aMask = (0xFF >> hardwareFormat.aLoss) << hardwareFormat.aShift;
+
+	if (hardwareFormat.bytesPerPixel == 2) {
+		uint16 *palette = (uint16 *)_cursor->getPalette() + _cursorKeyColor;
+		*palette &= ~aMask;
+	} else if (hardwareFormat.bytesPerPixel == 4) {
+		uint32 *palette = (uint32 *)_cursor->getPalette() + _cursorKeyColor;
+		*palette &= ~aMask;
+	} else {
+		warning("OpenGLGraphicsManager::updateCursorPalette: Unsupported pixel depth %d", hardwareFormat.bytesPerPixel);
+	}
 }
 
-void OpenGLGraphicsManager::setScale(int newScale) {
-	assert(_transactionMode == kTransactionActive);
-
-	if (newScale == _videoMode.scaleFactor)
+void OpenGLGraphicsManager::recalculateCursorScaling() {
+	if (!_cursor || !_gameScreen) {
 		return;
+	}
 
-	_videoMode.scaleFactor = newScale;
-	_transactionDetails.sizeChanged = true;
-}
+	// By default we use the unscaled versions.
+	_cursorHotspotXScaled = _cursorHotspotX;
+	_cursorHotspotYScaled = _cursorHotspotY;
+	_cursorWidthScaled = _cursor->getWidth();
+	_cursorHeightScaled = _cursor->getHeight();
 
-void OpenGLGraphicsManager::toggleAntialiasing() {
-	assert(_transactionMode == kTransactionActive);
+	// In case scaling is actually enabled we will scale the cursor according
+	// to the game screen.
+	if (!_cursorDontScale) {
+		const frac_t screenScaleFactorX = intToFrac(_displayWidth)  / _gameScreen->getWidth();
+		const frac_t screenScaleFactorY = intToFrac(_displayHeight) / _gameScreen->getHeight();
 
-	_videoMode.antialiasing = !_videoMode.antialiasing;
-	_transactionDetails.filterChanged = true;
-}
+		_cursorHotspotXScaled = fracToInt(_cursorHotspotXScaled * screenScaleFactorX);
+		_cursorWidthScaled    = fracToInt(_cursorWidthScaled    * screenScaleFactorX);
 
-uint OpenGLGraphicsManager::getAspectRatio() const {
-	// In case we enable aspect ratio correction we force a 4/3 ratio.
-	// But just for 320x200 and 640x400 games, since other games do not need
-	// this.
-	// TODO: This makes OpenGL Normal behave like OpenGL Conserve, when aspect
-	// ratio correction is enabled, but it's better than the previous 4/3 mode
-	// mess at least...
-	if (_videoMode.aspectRatioCorrection
-	        && ((_videoMode.screenWidth == 320 && _videoMode.screenHeight == 200)
-	            || (_videoMode.screenWidth == 640 && _videoMode.screenHeight == 400)))
-		return 13333;
-	else if (_videoMode.mode == OpenGL::GFX_NORMAL)
-		return _videoMode.hardwareWidth * 10000 / _videoMode.hardwareHeight;
-	else
-		return _videoMode.screenWidth * 10000 / _videoMode.screenHeight;
+		_cursorHotspotYScaled = fracToInt(_cursorHotspotYScaled * screenScaleFactorY);
+		_cursorHeightScaled   = fracToInt(_cursorHeightScaled   * screenScaleFactorY);
+	}
 }
 
-void OpenGLGraphicsManager::adjustMousePosition(int16 &x, int16 &y) {
-	if (_overlayVisible)
-		return;
-
-	x -= _displayX;
-	y -= _displayY;
-
-	if (_displayWidth != _videoMode.screenWidth)
-		x = x * _videoMode.screenWidth / _displayWidth;
-	if (_displayHeight != _videoMode.screenHeight)
-		y = y * _videoMode.screenHeight / _displayHeight;
+#ifdef USE_OSD
+const Graphics::Font *OpenGLGraphicsManager::getFontOSD() {
+	return FontMan.getFontByUsage(Graphics::FontManager::kLocalizedFont);
 }
+#endif
 
-bool OpenGLGraphicsManager::saveScreenshot(const char *filename) {
-	int width = _videoMode.hardwareWidth;
-	int height = _videoMode.hardwareHeight;
+void OpenGLGraphicsManager::saveScreenshot(const Common::String &filename) const {
+	const uint width  = _outputScreenWidth;
+	const uint height = _outputScreenHeight;
 
 	// A line of a BMP image must have a size divisible by 4.
 	// We calculate the padding bytes needed here.
 	// Since we use a 3 byte per pixel mode, we can use width % 4 here, since
 	// it is equal to 4 - (width * 3) % 4. (4 - (width * Bpp) % 4, is the
 	// usual way of computing the padding bytes required).
-	const int linePaddingSize = width % 4;
-	const int lineSize = width * 3 + linePaddingSize;
+	const uint linePaddingSize = width % 4;
+	const uint lineSize        = width * 3 + linePaddingSize;
 
 	// Allocate memory for screenshot
 	uint8 *pixels = new uint8[lineSize * height];
 
 	// Get pixel data from OpenGL buffer
-#ifdef USE_GLES
-	glReadPixels(0, 0, width, height, GL_RGB, GL_UNSIGNED_BYTE, pixels); CHECK_GL_ERROR();
-#else
-	if (_formatBGR) {
-		glReadPixels(0, 0, width, height, GL_BGR, GL_UNSIGNED_BYTE, pixels); CHECK_GL_ERROR();
-	} else {
-		glReadPixels(0, 0, width, height, GL_RGB, GL_UNSIGNED_BYTE, pixels); CHECK_GL_ERROR();
+	GLCALL(glReadPixels(0, 0, width, height, GL_RGB, GL_UNSIGNED_BYTE, pixels));
+
+	// BMP stores as BGR. Since we can't assume that GL_BGR is supported we
+	// will swap the components from the RGB we read to BGR on our own.
+	for (uint y = height; y-- > 0;) {
+		uint8 *line = pixels + y * lineSize;
+
+		for (uint x = width; x > 0; --x, line += 3) {
+			SWAP(line[0], line[2]);
+		}
 	}
-#endif
 
 	// Open file
 	Common::DumpFile out;
@@ -1324,73 +1161,6 @@ bool OpenGLGraphicsManager::saveScreenshot(const char *filename) {
 
 	// Free allocated memory
 	delete[] pixels;
-
-	return true;
 }
 
-const char *OpenGLGraphicsManager::getCurrentModeName() {
-	const char *modeName = 0;
-	const OSystem::GraphicsMode *g = getSupportedGraphicsModes();
-	while (g->name) {
-		if (g->id == _videoMode.mode) {
-			modeName = g->description;
-			break;
-		}
-		g++;
-	}
-	return modeName;
-}
-
-#ifdef USE_OSD
-const Graphics::Font *OpenGLGraphicsManager::getFontOSD() {
-	return FontMan.getFontByUsage(Graphics::FontManager::kLocalizedFont);
-}
-
-void OpenGLGraphicsManager::updateOSD() {
-	// The font we are going to use:
-	const Graphics::Font *font = getFontOSD();
-
-	if (_osdSurface.w != _osdTexture->getWidth() || _osdSurface.h != _osdTexture->getHeight())
-		_osdSurface.create(_osdTexture->getWidth(), _osdTexture->getHeight(), _overlayFormat);
-	else
-		// Clear everything
-		memset(_osdSurface.getPixels(), 0, _osdSurface.h * _osdSurface.pitch);
-
-	// Determine a rect which would contain the message string (clipped to the
-	// screen dimensions).
-	const int vOffset = 6;
-	const int lineSpacing = 1;
-	const int lineHeight = font->getFontHeight() + 2 * lineSpacing;
-	int width = 0;
-	int height = lineHeight * _osdLines.size() + 2 * vOffset;
-	for (uint i = 0; i < _osdLines.size(); i++) {
-		width = MAX(width, font->getStringWidth(_osdLines[i]) + 14);
-	}
-
-	// Clip the rect
-	if (width > _osdSurface.w)
-		width = _osdSurface.w;
-	if (height > _osdSurface.h)
-		height = _osdSurface.h;
-
-	int dstX = (_osdSurface.w - width) / 2;
-	int dstY = (_osdSurface.h - height) / 2;
-
-	// Draw a dark gray rect (R = 40, G = 40, B = 40)
-	const uint16 color = 0x294B;
-	_osdSurface.fillRect(Common::Rect(dstX, dstY, dstX + width, dstY + height), color);
-
-	// Render the message, centered, and in white
-	for (uint i = 0; i < _osdLines.size(); i++) {
-		font->drawString(&_osdSurface, _osdLines[i],
-		                 dstX, dstY + i * lineHeight + vOffset + lineSpacing, width,
-		                 0xFFFF, Graphics::kTextAlignCenter);
-	}
-
-	// Update the texture
-	_osdTexture->updateBuffer(_osdSurface.getPixels(), _osdSurface.pitch, 0, 0,
-	                          _osdSurface.w, _osdSurface.h);
-}
-#endif
-
-#endif
+} // End of namespace OpenGL
diff --git a/backends/graphics/opengl/opengl-graphics.h b/backends/graphics/opengl/opengl-graphics.h
index 9d8d418d11..d16f92d148 100644
--- a/backends/graphics/opengl/opengl-graphics.h
+++ b/backends/graphics/opengl/opengl-graphics.h
@@ -8,338 +8,483 @@
  * modify it under the terms of the GNU General Public License
  * as published by the Free Software Foundation; either version 2
  * of the License, or (at your option) any later version.
-
+ *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
-
+ *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  *
  */
 
-#ifndef BACKENDS_GRAPHICS_OPENGL_H
-#define BACKENDS_GRAPHICS_OPENGL_H
+#ifndef BACKENDS_GRAPHICS_OPENGL_OPENGL_GRAPHICS_H
+#define BACKENDS_GRAPHICS_OPENGL_OPENGL_GRAPHICS_H
 
-#include "backends/graphics/opengl/gltexture.h"
+#include "backends/graphics/opengl/opengl-sys.h"
 #include "backends/graphics/graphics.h"
-#include "common/array.h"
-#include "common/rect.h"
-#include "graphics/font.h"
-#include "graphics/pixelformat.h"
 
-// Uncomment this to enable the 'on screen display' code.
-#define USE_OSD	1
+#include "common/frac.h"
+#include "common/mutex.h"
+
+namespace Graphics {
+class Font;
+} // End of namespace Graphics
 
 namespace OpenGL {
-// The OpenGL GFX modes. They have to be inside the OpenGL namespace so they
-// do not clash with the SDL GFX modes.
+
+// HACK: We use glColor in the OSD code. This might not be working on GL ES but
+// we still enable it because Tizen already shipped with it. Also, the
+// SurfaceSDL backend enables it and disabling it can cause issues in sdl.cpp.
+#define USE_OSD 1
+
+class Texture;
+
 enum {
-	GFX_NORMAL = 0,
-	GFX_CONSERVE = 1,
-	GFX_ORIGINAL = 2
+	GFX_LINEAR = 0,
+	GFX_NEAREST = 1
 };
 
-}
-
-/**
- * OpenGL graphics manager. This is an abstract class, it does not do the
- * window and OpenGL context initialization.
- * Derived classes should at least override internUpdateScreen for doing
- * the buffers swap, and implement loadGFXMode for handling the window/context if
- * needed. If USE_RGB_COLOR is enabled, getSupportedFormats must be implemented.
- */
-class OpenGLGraphicsManager : public GraphicsManager {
+class OpenGLGraphicsManager : virtual public GraphicsManager {
 public:
 	OpenGLGraphicsManager();
 	virtual ~OpenGLGraphicsManager();
 
+	// GraphicsManager API
 	virtual bool hasFeature(OSystem::Feature f);
 	virtual void setFeatureState(OSystem::Feature f, bool enable);
 	virtual bool getFeatureState(OSystem::Feature f);
 
-	static const OSystem::GraphicsMode *supportedGraphicsModes();
 	virtual const OSystem::GraphicsMode *getSupportedGraphicsModes() const;
 	virtual int getDefaultGraphicsMode() const;
 	virtual bool setGraphicsMode(int mode);
 	virtual int getGraphicsMode() const;
-	virtual void resetGraphicsScale();
+
+	virtual void resetGraphicsScale() {}
+
 #ifdef USE_RGB_COLOR
 	virtual Graphics::PixelFormat getScreenFormat() const;
 	virtual Common::List<Graphics::PixelFormat> getSupportedFormats() const = 0;
 #endif
-	virtual void initSize(uint width, uint height, const Graphics::PixelFormat *format = NULL);
-	virtual int getScreenChangeID() const;
 
 	virtual void beginGFXTransaction();
 	virtual OSystem::TransactionError endGFXTransaction();
 
-	virtual int16 getHeight();
+	virtual int getScreenChangeID() const;
+
+	virtual void initSize(uint width, uint height, const Graphics::PixelFormat *format);
+
 	virtual int16 getWidth();
-protected:
-	// PaletteManager API
-	virtual void setPalette(const byte *colors, uint start, uint num);
-	virtual void grabPalette(byte *colors, uint start, uint num);
+	virtual int16 getHeight();
 
-public:
 	virtual void copyRectToScreen(const void *buf, int pitch, int x, int y, int w, int h);
-	virtual Graphics::Surface *lockScreen();
-	virtual void unlockScreen();
 	virtual void fillScreen(uint32 col);
-	virtual void updateScreen();
+
 	virtual void setShakePos(int shakeOffset);
-	virtual void setFocusRectangle(const Common::Rect &rect);
+
+	virtual void updateScreen();
+
+	virtual Graphics::Surface *lockScreen();
+	virtual void unlockScreen();
+
+	virtual void setFocusRectangle(const Common::Rect& rect);
 	virtual void clearFocusRectangle();
 
+	virtual int16 getOverlayWidth();
+	virtual int16 getOverlayHeight();
+
 	virtual void showOverlay();
 	virtual void hideOverlay();
+
 	virtual Graphics::PixelFormat getOverlayFormat() const;
+
+	virtual void copyRectToOverlay(const void *buf, int pitch, int x, int y, int w, int h);
 	virtual void clearOverlay();
 	virtual void grabOverlay(void *buf, int pitch);
-	virtual void copyRectToOverlay(const void *buf, int pitch, int x, int y, int w, int h);
-	virtual int16 getOverlayHeight();
-	virtual int16 getOverlayWidth();
 
 	virtual bool showMouse(bool visible);
 	virtual void warpMouse(int x, int y);
-	virtual void setMouseCursor(const void *buf, uint w, uint h, int hotspotX, int hotspotY, uint32 keycolor, bool dontScale = false, const Graphics::PixelFormat *format = NULL);
+	virtual void setMouseCursor(const void *buf, uint w, uint h, int hotspotX, int hotspotY, uint32 keycolor, bool dontScale, const Graphics::PixelFormat *format);
 	virtual void setCursorPalette(const byte *colors, uint start, uint num);
 
 	virtual void displayMessageOnOSD(const char *msg);
+
+	// PaletteManager interface
+	virtual void setPalette(const byte *colors, uint start, uint num);
+	virtual void grabPalette(byte *colors, uint start, uint num);
+
 protected:
 	/**
-	 * Setup OpenGL settings
+	 * Set up the actual screen size available for the OpenGL code to do any
+	 * drawing.
+	 *
+	 * @param width  The width of the screen.
+	 * @param height The height of the screen.
+	 */
+	void setActualScreenSize(uint width, uint height);
+
+	/**
+	 * Notify the manager of a OpenGL context change. This should be the first
+	 * thing to call after you created an OpenGL (ES) context!
+	 *
+	 * @param defaultFormat      The new default format for the game screen
+	 *                           (this is used for the CLUT8 game screens).
+	 * @param defaultFromatAlpha The new default format with an alpha channel
+	 *                           (this is used for the overlay and cursor).
+	 */
+	void notifyContextCreate(const Graphics::PixelFormat &defaultFormat, const Graphics::PixelFormat &defaultFormatAlpha);
+
+	/**
+	 * Notify the manager that the OpenGL context is about to be destroyed.
+	 * This will free up/reset internal OpenGL related state and *must* be
+	 * called whenever a context might be created again after destroying a
+	 * context.
 	 */
-	virtual void initGL();
+	void notifyContextDestroy();
 
 	/**
-	 * Creates and refreshs OpenGL textures.
+	 * Adjust the physical mouse coordinates according to the currently visible screen.
 	 */
-	virtual void loadTextures();
+	void adjustMousePosition(int16 &x, int16 &y);
+
+	/**
+	 * Set up the mouse position for graphics output.
+	 *
+	 * @param x X coordinate in physical coordinates.
+	 * @param y Y coordinate in physical coordinates.
+	 */
+	void setMousePosition(int x, int y) { _cursorX = x; _cursorY = y; }
+
+	/**
+	 * Query the mouse position in physical coordinates.
+	 */
+	void getMousePosition(int16 &x, int16 &y) const { x = _cursorX; y = _cursorY; }
+
+	/**
+	 * Set up the mouse position for the (event) system.
+	 *
+	 * @param x X coordinate in physical coordinates.
+	 * @param y Y coordinate in physical coordinates.
+	 */
+	virtual void setInternalMousePosition(int x, int y) = 0;
+
+private:
+	/**
+	 * Create a texture with the specified pixel format.
+	 *
+	 * @param format    The pixel format the Texture object should accept as
+	 *                  input.
+	 * @param wantAlpha For CLUT8 textures this marks whether an alpha
+	 *                  channel should be used.
+	 * @return A pointer to the texture or nullptr on failure.
+	 */
+	Texture *createTexture(const Graphics::PixelFormat &format, bool wantAlpha = false);
 
 	//
-	// GFX and video
+	// Transaction support
 	//
-	enum {
-		kTransactionNone = 0,
-		kTransactionActive = 1,
-		kTransactionRollback = 2
-	};
-
-	struct TransactionDetails {
-		bool sizeChanged;
-		bool needRefresh;
-		bool needUpdatescreen;
-		bool filterChanged;
+	struct VideoState {
+		VideoState() : valid(false), gameWidth(0), gameHeight(0),
 #ifdef USE_RGB_COLOR
-		bool formatChanged;
+		    gameFormat(),
 #endif
-	};
-	TransactionDetails _transactionDetails;
-	int _transactionMode;
-
-	struct VideoState {
-		bool setup;
+		    aspectRatioCorrection(false), graphicsMode(GFX_LINEAR) {
+		}
 
-		bool fullscreen;
+		bool valid;
 
-		int mode;
-		int scaleFactor;
-		bool antialiasing;
+		uint gameWidth, gameHeight;
+#ifdef USE_RGB_COLOR
+		Graphics::PixelFormat gameFormat;
+#endif
 		bool aspectRatioCorrection;
+		int graphicsMode;
 
-		int screenWidth, screenHeight;
-		int overlayWidth, overlayHeight;
-		int hardwareWidth, hardwareHeight;
+		bool operator==(const VideoState &right) {
+			return gameWidth == right.gameWidth && gameHeight == right.gameHeight
 #ifdef USE_RGB_COLOR
-		Graphics::PixelFormat format;
+			    && gameFormat == right.gameFormat
 #endif
+			    && aspectRatioCorrection == right.aspectRatioCorrection
+			    && graphicsMode == right.graphicsMode;
+		}
+
+		bool operator!=(const VideoState &right) {
+			return !(*this == right);
+		}
 	};
-	VideoState _videoMode, _oldVideoMode;
 
 	/**
-	 * Sets the OpenGL texture format for the given pixel format. If format is not support will raise an error.
+	 * The currently setup video state.
+	 */
+	VideoState _currentState;
+
+	/**
+	 * The old video state used when doing a transaction rollback.
 	 */
-	virtual void getGLPixelFormat(Graphics::PixelFormat pixelFormat, byte &bpp, GLenum &intFormat, GLenum &glFormat, GLenum &type);
+	VideoState _oldState;
+
+protected:
+	enum TransactionMode {
+		kTransactionNone = 0,
+		kTransactionActive = 1,
+		kTransactionRollback = 2
+	};
 
-	virtual void internUpdateScreen();
-	virtual bool loadGFXMode();
-	virtual void unloadGFXMode();
+	TransactionMode getTransactionMode() const { return _transactionMode; }
 
+private:
 	/**
-	 * Setup the fullscreen mode state.
+	 * The current transaction mode.
 	 */
-	void setFullscreenMode(bool enable);
+	TransactionMode _transactionMode;
 
 	/**
-	 * Query the fullscreen state.
+	 * The current screen change ID.
 	 */
-	inline bool getFullscreenMode() const { return _videoMode.fullscreen; }
+	int _screenChangeID;
 
+protected:
 	/**
-	 * Set the scale factor.
+	 * Set up the requested video mode. This takes parameters which describe
+	 * what resolution the game screen requests (this is possibly aspect ratio
+	 * corrected!).
 	 *
-	 * This can only be used in a GFX transaction.
+	 * A sub-class should take these parameters as hints. It might very well
+	 * set up a mode which it thinks suites the situation best.
 	 *
-	 * @param newScale New scale factor.
+	 * @parma requestedWidth  This is the requested actual game screen width.
+	 * @param requestedHeight This is the requested actual game screen height.
+	 * @param format          This is the requested pixel format of the virtual game screen.
+	 * @return true on success, false otherwise
 	 */
-	void setScale(int newScale);
+	virtual bool loadVideoMode(uint requestedWidth, uint requestedHeight, const Graphics::PixelFormat &format) = 0;
 
 	/**
-	 * Query the scale factor.
+	 * Save a screenshot of the full display as BMP to the given file. This
+	 * uses Common::DumpFile for writing the screenshot.
+	 *
+	 * @param filename The output filename.
 	 */
-	inline int getScale() const { return _videoMode.scaleFactor; }
+	void saveScreenshot(const Common::String &filename) const;
+
+private:
+	//
+	// OpenGL utilities
+	//
 
 	/**
-	 * Toggle the antialiasing state of the current video mode.
+	 * Try to determine the internal parameters for a given pixel format.
 	 *
-	 * This can only be used in a GFX transaction.
+	 * @return true when the format can be used, false otherwise.
 	 */
-	void toggleAntialiasing();
+	bool getGLPixelFormat(const Graphics::PixelFormat &pixelFormat, GLenum &glIntFormat, GLenum &glFormat, GLenum &glType) const;
+
+	//
+	// Actual hardware screen
+	//
 
 	/**
-	 * Query the antialiasing state.
+	 * The width of the physical output.
 	 */
-	inline bool getAntialiasingState() const { return _videoMode.antialiasing; }
+	uint _outputScreenWidth;
 
-	// Drawing coordinates for the current display mode and scale
-	int _displayX;
-	int _displayY;
-	int _displayWidth;
-	int _displayHeight;
+	/**
+	 * The height of the physical output.
+	 */
+	uint _outputScreenHeight;
 
-	virtual const char *getCurrentModeName();
+	/**
+	 * @return The desired aspect of the game screen.
+	 */
+	frac_t getDesiredGameScreenAspect() const;
 
-	virtual void calculateDisplaySize(int &width, int &height);
-	virtual void refreshDisplaySize();
+	/**
+	 * Recalculates the area used to display the game screen.
+	 */
+	void recalculateDisplayArea();
 
-	uint getAspectRatio() const;
+	/**
+	 * The X coordinate of the game screen.
+	 */
+	uint _displayX;
 
-	void setFormatIsBGR(bool isBGR) { _formatBGR = isBGR; }
-	bool _formatBGR;
+	/**
+	 * The Y coordinate of the game screen.
+	 */
+	uint _displayY;
+
+	/**
+	 * The width of the game screen in physical coordinates.
+	 */
+	uint _displayWidth;
+
+	/**
+	 * The height of the game screen in physical coordinates.
+	 */
+	uint _displayHeight;
+
+	/**
+	 * The default pixel format of the backend.
+	 */
+	Graphics::PixelFormat _defaultFormat;
+
+	/**
+	 * The default pixel format with an alpha channel.
+	 */
+	Graphics::PixelFormat _defaultFormatAlpha;
 
 	//
 	// Game screen
 	//
-	GLTexture *_gameTexture;
-	Graphics::Surface _screenData;
-	int _screenChangeCount;
-	bool _screenNeedsRedraw;
-	Common::Rect _screenDirtyRect;
 
-#ifdef USE_RGB_COLOR
-	Graphics::PixelFormat _screenFormat;
-#endif
-	byte *_gamePalette;
+	/**
+	 * The virtual game screen.
+	 */
+	Texture *_gameScreen;
 
-	virtual void refreshGameScreen();
+	/**
+	 * The game palette if in CLUT8 mode.
+	 */
+	byte _gamePalette[3 * 256];
 
-	// Shake mode
-	int _shakePos;
+	/**
+	 * The offset by which the screen is moved vertically.
+	 */
+	int _gameScreenShakeOffset;
 
 	//
 	// Overlay
 	//
-	GLTexture *_overlayTexture;
-	Graphics::Surface _overlayData;
-	Graphics::PixelFormat _overlayFormat;
-	bool _overlayVisible;
-	bool _overlayNeedsRedraw;
-	Common::Rect _overlayDirtyRect;
 
-	virtual void refreshOverlay();
+	/**
+	 * The overlay screen.
+	 */
+	Texture *_overlay;
+
+	/**
+	 * Whether the overlay is visible or not.
+	 */
+	bool _overlayVisible;
 
 	//
-	// Mouse
+	// Cursor
 	//
-	struct MousePos {
-		// The mouse position in hardware screen coordinates.
-		int16 x, y;
 
-		// The size and hotspot of the original cursor image.
-		int16 w, h;
-		int16 hotX, hotY;
+	/**
+	 * Set up the correct cursor palette.
+	 */
+	void updateCursorPalette();
 
-		// The size and hotspot of the scaled cursor, in real coordinates.
-		int16 rW, rH;
-		int16 rHotX, rHotY;
+	/**
+	 * The cursor image.
+	 */
+	Texture *_cursor;
 
-		// The size and hotspot of the scaled cursor, in game coordinates.
-		int16 vW, vH;
-		int16 vHotX, vHotY;
+	/**
+	 * X coordinate of the cursor in phyiscal coordinates.
+	 */
+	int _cursorX;
 
-		MousePos() : x(0), y(0), w(0), h(0), hotX(0), hotY(0),
-					rW(0), rH(0), rHotX(0), rHotY(0), vW(0), vH(0),
-					vHotX(0), vHotY(0)	{}
-	};
+	/**
+	 * Y coordinate of the cursor in physical coordinates.
+	 */
+	int _cursorY;
 
-	GLTexture *_cursorTexture;
-	Graphics::Surface _cursorData;
-	Graphics::PixelFormat _cursorFormat;
-	byte *_cursorPalette;
-	bool _cursorPaletteDisabled;
-	MousePos _cursorState;
-	bool _cursorVisible;
+	/**
+	 * The X offset for the cursor hotspot in unscaled coordinates.
+	 */
+	int _cursorHotspotX;
+
+	/**
+	 * The Y offset for the cursor hotspot in unscaled coordinates.
+	 */
+	int _cursorHotspotY;
+
+	/**
+	 * Recalculate the cursor scaling. Scaling is always done according to
+	 * the game screen.
+	 */
+	void recalculateCursorScaling();
+
+	/**
+	 * The X offset for the cursor hotspot in scaled coordinates.
+	 */
+	int _cursorHotspotXScaled;
+
+	/**
+	 * The Y offset for the cursor hotspot in scaled coordinates.
+	 */
+	int _cursorHotspotYScaled;
+
+	/**
+	 * The width of the cursor scaled coordinates.
+	 */
+	uint _cursorWidthScaled;
+
+	/**
+	 * The height of the cursor scaled coordinates.
+	 */
+	uint _cursorHeightScaled;
+
+	/**
+	 * The key color.
+	 */
 	uint32 _cursorKeyColor;
-	bool _cursorDontScale;
-	bool _cursorNeedsRedraw;
 
 	/**
-	 * Set up the mouse position for graphics output.
-	 *
-	 * @param x X coordinate in native coordinates.
-	 * @param y Y coordinate in native coordinates.
+	 * Whether the cursor is actually visible.
 	 */
-	void setMousePosition(int x, int y) { _cursorState.x = x; _cursorState.y = y; }
+	bool _cursorVisible;
 
-	virtual void refreshCursor();
-	virtual void refreshCursorScale();
+	/**
+	 * Whether no cursor scaling should be applied.
+	 */
+	bool _cursorDontScale;
 
 	/**
-	 * Set up the mouse position for the (event) system.
-	 *
-	 * @param x X coordinate in native coordinates.
-	 * @param y Y coordinate in native coordinates.
+	 * Whether the special cursor palette is enabled.
 	 */
-	virtual void setInternalMousePosition(int x, int y) = 0;
+	bool _cursorPaletteEnabled;
 
 	/**
-	 * Adjusts hardware screen coordinates to either overlay or game screen
-	 * coordinates depending on whether the overlay is visible or not.
-	 *
-	 * @param x X coordinate of the mouse position.
-	 * @param y Y coordinate of the mouse position.
+	 * The special cursor palette in case enabled.
 	 */
-	virtual void adjustMousePosition(int16 &x, int16 &y);
+	byte _cursorPalette[3 * 256];
 
+#ifdef USE_OSD
 	//
-	// Misc
+	// OSD
 	//
-	virtual bool saveScreenshot(const char *filename);
-
-#ifdef USE_OSD
+protected:
 	/**
 	 * Returns the font used for on screen display
 	 */
 	virtual const Graphics::Font *getFontOSD();
 
+private:
 	/**
-	 * Update the OSD texture / surface.
+	 * The OSD's contents.
 	 */
-	void updateOSD();
+	Texture *_osd;
 
 	/**
-	 * The OSD contents.
+	 * Current opacity level of the OSD.
 	 */
-	Common::Array<Common::String> _osdLines;
-
-	GLTexture *_osdTexture;
-	Graphics::Surface _osdSurface;
 	uint8 _osdAlpha;
+
+	/**
+	 * When fading the OSD has started.
+	 */
 	uint32 _osdFadeStartTime;
-	bool _requireOSDUpdate;
+
+	/**
+	 * Mutex to allow displayMessageOnOSD to be used from the audio thread.
+	 */
+	Common::Mutex _osdMutex;
+
 	enum {
 		kOSDFadeOutDelay = 2 * 1000,
 		kOSDFadeOutDuration = 500,
@@ -348,4 +493,6 @@ protected:
 #endif
 };
 
+} // End of namespace OpenGL
+
 #endif
diff --git a/backends/graphics/opengl/glerrorcheck.cpp b/backends/graphics/opengl/opengl-sys.h
index 439593577d..a3524b28d2 100644
--- a/backends/graphics/opengl/glerrorcheck.cpp
+++ b/backends/graphics/opengl/opengl-sys.h
@@ -8,25 +8,25 @@
  * modify it under the terms of the GNU General Public License
  * as published by the Free Software Foundation; either version 2
  * of the License, or (at your option) any later version.
-
+ *
  * This program is distributed in the hope that it will be useful,
  * but WITHOUT ANY WARRANTY; without even the implied warranty of
- * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.	 See the
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  * GNU General Public License for more details.
-
+ *
  * You should have received a copy of the GNU General Public License
  * along with this program; if not, write to the Free Software
  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
  *
  */
 
-#include "common/scummsys.h"
+#ifndef BACKENDS_GRAPHICS_OPENGL_OPENGL_H
+#define BACKENDS_GRAPHICS_OPENGL_OPENGL_H
 
-#if defined(DEBUG) && defined(USE_OPENGL)
+// The purpose of this header is to include the OpenGL headers in an uniform
+// fashion. A notable example for a non standard port is the Tizen port.
 
-#include "backends/graphics/opengl/glerrorcheck.h"
-#include "common/textconsole.h"
-#include "common/str.h"
+#include "common/scummsys.h"
 
 #ifdef WIN32
 #if defined(ARRAYSIZE) && !defined(_WINDOWS_)
@@ -37,31 +37,21 @@
 #undef ARRAYSIZE
 #endif
 
-#if defined(USE_GLES)
+// HACK: In case common/util.h has been included already we need to make sure
+// to define ARRAYSIZE again in case of Windows.
+#if !defined(ARRAYSIZE) && defined(COMMON_UTIL_H)
+#define ARRAYSIZE(x) ((int)(sizeof(x) / sizeof(x[0])))
+#endif
+
+#if defined(TIZEN)
+#include <FGraphicsOpengl.h>
+using namespace Tizen::Graphics::Opengl;
+#elif defined(USE_GLES)
 #include <GLES/gl.h>
-#elif defined(MACOSX)
-#include <OpenGL/gl.h>
+#elif defined(SDL_BACKEND)
+#include <SDL_opengl.h>
 #else
 #include <GL/gl.h>
 #endif
 
-static Common::String getGlErrStr(GLenum error) {
-	switch (error) {
-	case GL_NO_ERROR:           return "GL_NO_ERROR";
-	case GL_INVALID_ENUM:       return "GL_INVALID_ENUM";
-	case GL_INVALID_OPERATION:  return "GL_INVALID_OPERATION";
-	case GL_STACK_OVERFLOW:     return "GL_STACK_OVERFLOW";
-	case GL_STACK_UNDERFLOW:    return "GL_STACK_UNDERFLOW";
-	case GL_OUT_OF_MEMORY:      return "GL_OUT_OF_MEMORY";
-	}
-
-	return Common::String::format("(Unknown GL error code 0x%x)", error);
-}
-
-void checkGlError(const char *file, int line) {
-	GLenum error = glGetError();
-	if (error != GL_NO_ERROR)
-		warning("%s:%d: GL error: %s", file, line, getGlErrStr(error).c_str());
-}
-
 #endif
diff --git a/backends/graphics/opengl/texture.cpp b/backends/graphics/opengl/texture.cpp
new file mode 100644
index 0000000000..7b0b22d630
--- /dev/null
+++ b/backends/graphics/opengl/texture.cpp
@@ -0,0 +1,374 @@
+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+#include "backends/graphics/opengl/texture.h"
+#include "backends/graphics/opengl/extensions.h"
+#include "backends/graphics/opengl/debug.h"
+
+#include "common/rect.h"
+#include "common/textconsole.h"
+
+namespace OpenGL {
+
+static GLuint nextHigher2(GLuint v) {
+	if (v == 0)
+		return 1;
+	v--;
+	v |= v >> 1;
+	v |= v >> 2;
+	v |= v >> 4;
+	v |= v >> 8;
+	v |= v >> 16;
+	return ++v;
+}
+
+GLint Texture::_maxTextureSize = 0;
+
+void Texture::queryTextureInformation() {
+	glGetIntegerv(GL_MAX_TEXTURE_SIZE, &_maxTextureSize);
+	debug(5, "OpenGL maximum texture size: %d", _maxTextureSize);
+}
+
+Texture::Texture(GLenum glIntFormat, GLenum glFormat, GLenum glType, const Graphics::PixelFormat &format)
+    : _glIntFormat(glIntFormat), _glFormat(glFormat), _glType(glType), _format(format), _glFilter(GL_NEAREST),
+      _glTexture(0), _textureData(), _userPixelData(), _allDirty(false) {
+	recreateInternalTexture();
+}
+
+Texture::~Texture() {
+	releaseInternalTexture();
+	_textureData.free();
+}
+
+void Texture::releaseInternalTexture() {
+	GLCALL(glDeleteTextures(1, &_glTexture));
+	_glTexture = 0;
+}
+
+void Texture::recreateInternalTexture() {
+	// Release old texture name in case it exists.
+	releaseInternalTexture();
+
+	// Get a new texture name.
+	GLCALL(glGenTextures(1, &_glTexture));
+
+	// Set up all texture parameters.
+	GLCALL(glBindTexture(GL_TEXTURE_2D, _glTexture));
+	GLCALL(glPixelStorei(GL_UNPACK_ALIGNMENT, 1));
+	GLCALL(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, _glFilter));
+	GLCALL(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, _glFilter));
+	GLCALL(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE));
+	GLCALL(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE));
+
+	// In case there is an actual texture setup we reinitialize it.
+	if (_textureData.getPixels()) {
+		// Allocate storage for OpenGL texture.
+		GLCALL(glTexImage2D(GL_TEXTURE_2D, 0, _glIntFormat, _textureData.w,
+		       _textureData.h, 0, _glFormat, _glType, NULL));
+
+		// Mark dirts such that it will be completely refreshed the next time.
+		flagDirty();
+	}
+}
+
+void Texture::enableLinearFiltering(bool enable) {
+	if (enable) {
+		_glFilter = GL_LINEAR;
+	} else {
+		_glFilter = GL_NEAREST;
+	}
+
+	GLCALL(glBindTexture(GL_TEXTURE_2D, _glTexture));
+
+	GLCALL(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MAG_FILTER, _glFilter));
+	GLCALL(glTexParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, _glFilter));
+}
+
+void Texture::allocate(uint width, uint height) {
+	uint texWidth = width, texHeight = height;
+	if (!g_extNPOTSupported) {
+		texWidth  = nextHigher2(texWidth);
+		texHeight = nextHigher2(texHeight);
+	}
+
+	// In case the needed texture dimension changed we will reinitialize the
+	// texture.
+	if (texWidth != _textureData.w || texHeight != _textureData.h) {
+		// Create a buffer for the texture data.
+		_textureData.create(texWidth, texHeight, _format);
+
+		// Set the texture.
+		GLCALL(glBindTexture(GL_TEXTURE_2D, _glTexture));
+
+		// Allocate storage for OpenGL texture.
+		GLCALL(glTexImage2D(GL_TEXTURE_2D, 0, _glIntFormat, _textureData.w,
+		       _textureData.h, 0, _glFormat, _glType, NULL));
+	}
+
+	// Create a sub-buffer for raw access.
+	_userPixelData = _textureData.getSubArea(Common::Rect(width, height));
+}
+
+void Texture::copyRectToTexture(uint x, uint y, uint w, uint h, const void *srcPtr, uint srcPitch) {
+	Graphics::Surface *dstSurf = getSurface();
+	assert(x + w <= dstSurf->w);
+	assert(y + h <= dstSurf->h);
+
+	// *sigh* Common::Rect::extend behaves unexpected whenever one of the two
+	// parameters is an empty rect. Thus, we check whether the current dirty
+	// area is valid. In case it is not we simply use the parameters as new
+	// dirty area. Otherwise, we simply call extend.
+	if (_dirtyArea.isEmpty()) {
+		_dirtyArea = Common::Rect(x, y, x + w, y + h);
+	} else {
+		_dirtyArea.extend(Common::Rect(x, y, x + w, y + h));
+	}
+
+	const byte *src = (const byte *)srcPtr;
+	byte *dst = (byte *)dstSurf->getBasePtr(x, y);
+	const uint pitch = dstSurf->pitch;
+	const uint bytesPerPixel = dstSurf->format.bytesPerPixel;
+
+	if (srcPitch == pitch && x == 0 && w == dstSurf->w) {
+		memcpy(dst, src, h * pitch);
+	} else {
+		while (h-- > 0) {
+			memcpy(dst, src, w * bytesPerPixel);
+			dst += pitch;
+			src += srcPitch;
+		}
+	}
+}
+
+void Texture::fill(uint32 color) {
+	Graphics::Surface *dst = getSurface();
+	dst->fillRect(Common::Rect(dst->w, dst->h), color);
+
+	flagDirty();
+}
+
+void Texture::draw(GLfloat x, GLfloat y, GLfloat w, GLfloat h) {
+	// Only do any processing when the Texture is initialized.
+	if (!_textureData.getPixels()) {
+		return;
+	}
+
+	// First update any potentional changes.
+	updateTexture();
+
+	// Set the texture.
+	GLCALL(glBindTexture(GL_TEXTURE_2D, _glTexture));
+
+	// Calculate the texture rect that will be drawn.
+	const GLfloat texWidth = (GLfloat)_userPixelData.w / _textureData.w;
+	const GLfloat texHeight = (GLfloat)_userPixelData.h / _textureData.h;
+	const GLfloat texcoords[4*2] = {
+		0,        0,
+		texWidth, 0,
+		0,        texHeight,
+		texWidth, texHeight
+	};
+	GLCALL(glTexCoordPointer(2, GL_FLOAT, 0, texcoords));
+
+	// Calculate the screen rect where the texture will be drawn.
+	const GLfloat vertices[4*2] = {
+		x,     y,
+		x + w, y,
+		x,     y + h,
+		x + w, y + h
+	};
+	GLCALL(glVertexPointer(2, GL_FLOAT, 0, vertices));
+
+	// Draw the texture to the screen buffer.
+	GLCALL(glDrawArrays(GL_TRIANGLE_STRIP, 0, 4));
+}
+
+void Texture::updateTexture() {
+	if (!isDirty()) {
+		return;
+	}
+
+	Common::Rect dirtyArea = getDirtyArea();
+
+	// In case we use linear filtering we might need to duplicate the last
+	// pixel row/column to avoid glitches with filtering.
+	if (_glFilter == GL_LINEAR) {
+		if (dirtyArea.right == _userPixelData.w && _userPixelData.w != _textureData.w) {
+			uint height = dirtyArea.height();
+
+			const byte *src = (const byte *)_textureData.getBasePtr(_userPixelData.w - 1, dirtyArea.top);
+			byte *dst = (byte *)_textureData.getBasePtr(_userPixelData.w, dirtyArea.top);
+
+			while (height-- > 0) {
+				memcpy(dst, src, _textureData.format.bytesPerPixel);
+				dst += _textureData.pitch;
+				src += _textureData.pitch;
+			}
+
+			// Extend the dirty area.
+			++dirtyArea.right;
+		}
+
+		if (dirtyArea.bottom == _userPixelData.h && _userPixelData.h != _textureData.h) {
+			const byte *src = (const byte *)_textureData.getBasePtr(dirtyArea.left, _userPixelData.h - 1);
+			byte *dst = (byte *)_textureData.getBasePtr(dirtyArea.left, _userPixelData.h);
+			memcpy(dst, src, dirtyArea.width() * _textureData.format.bytesPerPixel);
+
+			// Extend the dirty area.
+			++dirtyArea.bottom;
+		}
+	}
+
+	// Set the texture.
+	GLCALL(glBindTexture(GL_TEXTURE_2D, _glTexture));
+
+	// Update the actual texture.
+	// Although we keep track of the dirty part of the texture buffer we
+	// cannot take advantage of the left/right boundries here because it is
+	// not possible to specify a pitch to glTexSubImage2D. To be precise, with
+	// plain OpenGL we could set GL_UNPACK_ROW_LENGTH to achieve this. However,
+	// OpenGL ES 1.0 does not support GL_UNPACK_ROW_LENGTH. Thus, we are left
+	// with the following options:
+	//
+	// 1) (As we do right now) Simply always update the whole texture lines of
+	//    rect changed. This is simplest to implement. In case performance is
+	//    really an issue we can think of switching to another method.
+	//
+	// 2) Copy the dirty rect to a temporary buffer and upload that by using
+	//    glTexSubImage2D. This is what the Android backend does. It is more
+	//    complicated though.
+	//
+	// 3) Use glTexSubImage2D per line changed. This is what the old OpenGL
+	//    graphics manager did but it is much slower! Thus, we do not use it.
+	GLCALL(glTexSubImage2D(GL_TEXTURE_2D, 0, 0, dirtyArea.top, _textureData.w, dirtyArea.height(),
+	                       _glFormat, _glType, _textureData.getBasePtr(0, dirtyArea.top)));
+
+	// We should have handled everything, thus not dirty anymore.
+	clearDirty();
+}
+
+Common::Rect Texture::getDirtyArea() const {
+	if (_allDirty) {
+		return Common::Rect(_userPixelData.w, _userPixelData.h);
+	} else {
+		return _dirtyArea;
+	}
+}
+
+TextureCLUT8::TextureCLUT8(GLenum glIntFormat, GLenum glFormat, GLenum glType, const Graphics::PixelFormat &format)
+    : Texture(glIntFormat, glFormat, glType, format), _clut8Data(), _palette(new byte[256 * format.bytesPerPixel]) {
+	memset(_palette, 0, sizeof(byte) * format.bytesPerPixel);
+}
+
+TextureCLUT8::~TextureCLUT8() {
+	delete[] _palette;
+	_palette = nullptr;
+	_clut8Data.free();
+}
+
+void TextureCLUT8::allocate(uint width, uint height) {
+	Texture::allocate(width, height);
+
+	// We only need to reinitialize our CLUT8 surface when the output size
+	// changed.
+	if (width == _clut8Data.w && height == _clut8Data.h) {
+		return;
+	}
+
+	_clut8Data.create(width, height, Graphics::PixelFormat::createFormatCLUT8());
+}
+
+Graphics::PixelFormat TextureCLUT8::getFormat() const {
+	return Graphics::PixelFormat::createFormatCLUT8();
+}
+
+namespace {
+template<typename ColorType>
+inline void convertPalette(ColorType *dst, const byte *src, uint colors, const Graphics::PixelFormat &format) {
+	while (colors-- > 0) {
+		*dst++ = format.RGBToColor(src[0], src[1], src[2]);
+		src += 3;
+	}
+}
+} // End of anonymous namespace
+
+void TextureCLUT8::setPalette(uint start, uint colors, const byte *palData) {
+	const Graphics::PixelFormat &hardwareFormat = getHardwareFormat();
+
+	if (hardwareFormat.bytesPerPixel == 2) {
+		convertPalette<uint16>((uint16 *)_palette + start, palData, colors, hardwareFormat);
+	} else if (hardwareFormat.bytesPerPixel == 4) {
+		convertPalette<uint32>((uint32 *)_palette + start, palData, colors, hardwareFormat);
+	} else {
+		warning("TextureCLUT8::setPalette: Unsupported pixel depth: %d", hardwareFormat.bytesPerPixel);
+	}
+
+	// A palette changes means we need to refresh the whole surface.
+	flagDirty();
+}
+
+namespace {
+template<typename PixelType>
+inline void doPaletteLookUp(PixelType *dst, const byte *src, uint width, uint height, uint dstPitch, uint srcPitch, const PixelType *palette) {
+	uint srcAdd = srcPitch - width;
+	uint dstAdd = dstPitch - width * sizeof(PixelType);
+
+	while (height-- > 0) {
+		for (uint x = width; x > 0; --x) {
+			*dst++ = palette[*src++];
+		}
+
+		dst = (PixelType *)((byte *)dst + dstAdd);
+		src += srcAdd;
+	}
+}
+} // End of anonymous namespace
+
+void TextureCLUT8::updateTexture() {
+	if (!isDirty()) {
+		return;
+	}
+
+	// Do the palette look up
+	Graphics::Surface *outSurf = Texture::getSurface();
+
+	Common::Rect dirtyArea = getDirtyArea();
+
+	if (outSurf->format.bytesPerPixel == 2) {
+		doPaletteLookUp<uint16>((uint16 *)outSurf->getBasePtr(dirtyArea.left, dirtyArea.top),
+		                        (const byte *)_clut8Data.getBasePtr(dirtyArea.left, dirtyArea.top),
+		                        dirtyArea.width(), dirtyArea.height(),
+		                        outSurf->pitch, _clut8Data.pitch, (const uint16 *)_palette);
+	} else if (outSurf->format.bytesPerPixel == 4) {
+		doPaletteLookUp<uint32>((uint32 *)outSurf->getBasePtr(dirtyArea.left, dirtyArea.top),
+		                        (const byte *)_clut8Data.getBasePtr(dirtyArea.left, dirtyArea.top),
+		                        dirtyArea.width(), dirtyArea.height(),
+		                        outSurf->pitch, _clut8Data.pitch, (const uint32 *)_palette);
+	} else {
+		warning("TextureCLUT8::updateTexture: Unsupported pixel depth: %d", outSurf->format.bytesPerPixel);
+	}
+
+	// Do generic handling of updating the texture.
+	Texture::updateTexture();
+}
+
+} // End of namespace OpenGL
diff --git a/backends/graphics/opengl/texture.h b/backends/graphics/opengl/texture.h
new file mode 100644
index 0000000000..ad70833544
--- /dev/null
+++ b/backends/graphics/opengl/texture.h
@@ -0,0 +1,175 @@
+/* ScummVM - Graphic Adventure Engine
+ *
+ * ScummVM is the legal property of its developers, whose names
+ * are too numerous to list here. Please refer to the COPYRIGHT
+ * file distributed with this source distribution.
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
+ *
+ */
+
+#ifndef BACKENDS_GRAPHICS_OPENGL_TEXTURE_H
+#define BACKENDS_GRAPHICS_OPENGL_TEXTURE_H
+
+#include "backends/graphics/opengl/opengl-sys.h"
+
+#include "graphics/pixelformat.h"
+#include "graphics/surface.h"
+
+#include "common/rect.h"
+
+namespace OpenGL {
+
+/**
+ * An OpenGL texture wrapper. It automatically takes care of all OpenGL
+ * texture handling issues and also provides access to the texture data.
+ */
+class Texture {
+public:
+	/**
+	 * Create a new texture with the specific internal format.
+	 *
+	 * @param glIntFormat The internal format to use.
+	 * @param glFormat    The input format.
+	 * @param glType      The input type.
+	 * @param format      The format used for the texture input.
+	 */
+	Texture(GLenum glIntFormat, GLenum glFormat, GLenum glType, const Graphics::PixelFormat &format);
+	virtual ~Texture();
+
+	/**
+	 * Destroy the OpenGL texture name.
+	 */
+	void releaseInternalTexture();
+
+	/**
+	 * Create the OpenGL texture name and flag the whole texture as dirty.
+	 */
+	void recreateInternalTexture();
+
+	/**
+	 * Enable or disable linear texture filtering.
+	 *
+	 * @param enable true to enable and false to disable.
+	 */
+	void enableLinearFiltering(bool enable);
+
+	/**
+	 * Allocate texture space for the desired dimensions. This wraps any
+	 * handling of requirements for POT textures.
+	 *
+	 * @param width  The desired logical width.
+	 * @param height The desired logical height.
+	 */
+	virtual void allocate(uint width, uint height);
+
+	void copyRectToTexture(uint x, uint y, uint w, uint h, const void *src, uint srcPitch);
+
+	void fill(uint32 color);
+
+	void draw(GLfloat x, GLfloat y, GLfloat w, GLfloat h);
+
+	void flagDirty() { _allDirty = true; }
+	bool isDirty() const { return _allDirty || !_dirtyArea.isEmpty(); }
+
+	uint getWidth() const { return _userPixelData.w; }
+	uint getHeight() const { return _userPixelData.h; }
+
+	/**
+	 * @return The hardware format of the texture data.
+	 */
+	const Graphics::PixelFormat &getHardwareFormat() const { return _format; }
+
+	/**
+	 * @return The logical format of the texture data.
+	 */
+	virtual Graphics::PixelFormat getFormat() const { return _format; }
+
+	virtual Graphics::Surface *getSurface() { return &_userPixelData; }
+	virtual const Graphics::Surface *getSurface() const { return &_userPixelData; }
+
+	/**
+	 * @return Whether the texture data is using a palette.
+	 */
+	virtual bool hasPalette() const { return false; }
+
+	virtual void setPalette(uint start, uint colors, const byte *palData) {}
+
+	virtual void *getPalette() { return 0; }
+	virtual const void *getPalette() const { return 0; }
+
+	/**
+	 * Query texture related OpenGL information from the context. This only
+	 * queries the maximum texture size for now.
+	 */
+	static void queryTextureInformation();
+
+	/**
+	 * @return Return the maximum texture dimensions supported.
+	 */
+	static GLint getMaximumTextureSize() { return _maxTextureSize; }
+protected:
+	virtual void updateTexture();
+
+	Common::Rect getDirtyArea() const;
+private:
+	const GLenum _glIntFormat;
+	const GLenum _glFormat;
+	const GLenum _glType;
+	const Graphics::PixelFormat _format;
+
+	GLint _glFilter;
+	GLuint _glTexture;
+
+	Graphics::Surface _textureData;
+	Graphics::Surface _userPixelData;
+
+	bool _allDirty;
+	Common::Rect _dirtyArea;
+	void clearDirty() { _allDirty = false; _dirtyArea = Common::Rect(); }
+
+	static GLint _maxTextureSize;
+};
+
+class TextureCLUT8 : public Texture {
+public:
+	TextureCLUT8(GLenum glIntFormat, GLenum glFormat, GLenum glType, const Graphics::PixelFormat &format);
+	virtual ~TextureCLUT8();
+
+	virtual void allocate(uint width, uint height);
+
+	virtual Graphics::PixelFormat getFormat() const;
+
+	virtual bool hasPalette() const { return true; }
+
+	virtual void setPalette(uint start, uint colors, const byte *palData);
+
+	virtual void *getPalette() { return _palette; }
+	virtual const void *getPalette() const { return _palette; }
+
+	virtual Graphics::Surface *getSurface() { return &_clut8Data; }
+	virtual const Graphics::Surface *getSurface() const { return &_clut8Data; }
+
+protected:
+	virtual void updateTexture();
+
+private:
+	Graphics::Surface _clut8Data;
+	byte *_palette;
+};
+
+} // End of namespace OpenGL
+
+#endif