OPENGL: Introduce abstraction for framebuffer.

This allows us to use various framebuffer settings easily. Now the GPU
accelerated CLUT8 surface implementation does not need to query former
framebuffer state anymore.

9 files changed, 488 insertions, 132 deletions

diff --git a/backends/graphics/opengl/context.cpp b/backends/graphics/opengl/context.cpp
index 7402e79ea5..d9c40859dc 100644
--- a/backends/graphics/opengl/context.cpp
+++ b/backends/graphics/opengl/context.cpp
@@ -24,6 +24,7 @@
 #include "backends/graphics/opengl/opengl-graphics.h"
 #include "backends/graphics/opengl/shader.h"
 #include "backends/graphics/opengl/pipeline.h"
+#include "backends/graphics/opengl/framebuffer.h"
 
 #include "common/tokenizer.h"
 #include "common/debug.h"
@@ -42,9 +43,24 @@ void Context::reset() {
 #include "backends/graphics/opengl/opengl-func.h"
 #undef GL_FUNC_DEF
 
+	activeFramebuffer = nullptr;
 	activePipeline = nullptr;
 }
 
+Framebuffer *Context::setFramebuffer(Framebuffer *framebuffer) {
+	Framebuffer *oldFramebuffer = activeFramebuffer;
+	if (oldFramebuffer) {
+		oldFramebuffer->deactivate();
+	}
+
+	activeFramebuffer = framebuffer;
+	if (activeFramebuffer) {
+		activeFramebuffer->activate();
+	}
+
+	return oldFramebuffer;
+}
+
 Pipeline *Context::setPipeline(Pipeline *pipeline) {
 	Pipeline *oldPipeline = activePipeline;
 
diff --git a/backends/graphics/opengl/framebuffer.cpp b/backends/graphics/opengl/framebuffer.cpp
new file mode 100644
index 0000000000..cca00bab03
--- /dev/null
+++ b/backends/graphics/opengl/framebuffer.cpp
@@ -0,0 +1,251 @@
+/* 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/framebuffer.h"
+#include "backends/graphics/opengl/texture.h"
+
+namespace OpenGL {
+
+Framebuffer::Framebuffer()
+    : _viewport(), _projectionMatrix(), _isActive(false), _clearColor(),
+      _blendState(false), _scissorTestState(false), _scissorBox() {
+}
+
+void Framebuffer::activate() {
+	_isActive = true;
+
+	applyViewport();
+	applyClearColor();
+	applyBlendState();
+	applyScissorTestState();
+	applyScissorBox();
+}
+
+void Framebuffer::deactivate() {
+	_isActive = false;
+}
+
+void Framebuffer::setClearColor(GLfloat r, GLfloat g, GLfloat b, GLfloat a) {
+	_clearColor[0] = r;
+	_clearColor[1] = g;
+	_clearColor[2] = b;
+	_clearColor[3] = a;
+
+	// Directly apply changes when we are active.
+	if (isActive()) {
+		applyClearColor();
+	}
+}
+
+void Framebuffer::enableBlend(bool enable) {
+	_blendState = enable;
+
+	// Directly apply changes when we are active.
+	if (isActive()) {
+		applyBlendState();
+	}
+}
+
+void Framebuffer::enableScissorTest(bool enable) {
+	_scissorTestState = enable;
+
+	// Directly apply changes when we are active.
+	if (isActive()) {
+		applyScissorTestState();
+	}
+}
+
+void Framebuffer::setScissorBox(GLint x, GLint y, GLsizei w, GLsizei h) {
+	_scissorBox[0] = x;
+	_scissorBox[1] = y;
+	_scissorBox[2] = w;
+	_scissorBox[3] = h;
+
+	// Directly apply changes when we are active.
+	if (isActive()) {
+		applyScissorBox();
+	}
+}
+
+void Framebuffer::applyViewport() {
+	GL_CALL(glViewport(_viewport[0], _viewport[1], _viewport[2], _viewport[3]));
+}
+
+void Framebuffer::applyClearColor() {
+	GL_CALL(glClearColor(_clearColor[0], _clearColor[1], _clearColor[2], _clearColor[3]));
+}
+
+void Framebuffer::applyBlendState() {
+	if (_blendState) {
+		GL_CALL(glEnable(GL_BLEND));
+	} else {
+		GL_CALL(glDisable(GL_BLEND));
+	}
+}
+
+void Framebuffer::applyScissorTestState() {
+	if (_scissorTestState) {
+		GL_CALL(glEnable(GL_SCISSOR_TEST));
+	} else {
+		GL_CALL(glDisable(GL_SCISSOR_TEST));
+	}
+}
+
+void Framebuffer::applyScissorBox() {
+	GL_CALL(glScissor(_scissorBox[0], _scissorBox[1], _scissorBox[2], _scissorBox[3]));
+}
+
+//
+// Backbuffer implementation
+//
+
+void Backbuffer::activate() {
+	Framebuffer::activate();
+
+#if !USE_FORCED_GLES
+	if (g_context.framebufferObjectSupported) {
+		GL_CALL(glBindFramebuffer(GL_FRAMEBUFFER, 0));
+	}
+#endif
+}
+
+void Backbuffer::setDimensions(uint width, uint height) {
+	// Set viewport dimensions.
+	_viewport[0] = 0;
+	_viewport[1] = 0;
+	_viewport[2] = width;
+	_viewport[3] = height;
+
+	// Setup orthogonal projection matrix.
+	_projectionMatrix[ 0] =  2.0f / width;
+	_projectionMatrix[ 1] =  0.0f;
+	_projectionMatrix[ 2] =  0.0f;
+	_projectionMatrix[ 3] =  0.0f;
+
+	_projectionMatrix[ 4] =  0.0f;
+	_projectionMatrix[ 5] = -2.0f / height;
+	_projectionMatrix[ 6] =  0.0f;
+	_projectionMatrix[ 7] =  0.0f;
+
+	_projectionMatrix[ 8] =  0.0f;
+	_projectionMatrix[ 9] =  0.0f;
+	_projectionMatrix[10] =  0.0f;
+	_projectionMatrix[11] =  0.0f;
+
+	_projectionMatrix[12] = -1.0f;
+	_projectionMatrix[13] =  1.0f;
+	_projectionMatrix[14] =  0.0f;
+	_projectionMatrix[15] =  1.0f;
+
+	// Directly apply changes when we are active.
+	if (isActive()) {
+		applyViewport();
+	}
+}
+
+//
+// Render to texture target implementation
+//
+
+#if !USE_FORCED_GLES
+TextureTarget::TextureTarget()
+    : _texture(new GLTexture(GL_RGBA, GL_RGBA, GL_UNSIGNED_BYTE)), _glFBO(0), _needUpdate(true) {
+}
+
+TextureTarget::~TextureTarget() {
+	delete _texture;
+	GL_CALL_SAFE(glDeleteFramebuffers, (1, &_glFBO));
+}
+
+void TextureTarget::activate() {
+	Framebuffer::activate();
+
+	// Allocate framebuffer object if necessary.
+	if (!_glFBO) {
+		GL_CALL(glGenFramebuffers(1, &_glFBO));
+		_needUpdate = true;
+	}
+
+	// Attach destination texture to FBO.
+	GL_CALL(glBindFramebuffer(GL_FRAMEBUFFER, _glFBO));
+
+	// If required attach texture to FBO.
+	if (_needUpdate) {
+		GL_CALL(glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, _texture->getGLTexture(), 0));
+		_needUpdate = false;
+	}
+}
+
+void TextureTarget::destroy() {
+	GL_CALL(glDeleteFramebuffers(1, &_glFBO));
+	_glFBO = 0;
+
+	_texture->destroy();
+}
+
+void TextureTarget::create() {
+	_texture->create();
+
+	_needUpdate = true;
+}
+
+void TextureTarget::setSize(uint width, uint height) {
+	_texture->setSize(width, height);
+
+	const uint texWidth  = _texture->getWidth();
+	const uint texHeight = _texture->getHeight();
+
+	// Set viewport dimensions.
+	_viewport[0] = 0;
+	_viewport[1] = 0;
+	_viewport[2] = texWidth;
+	_viewport[3] = texHeight;
+
+	// Setup orthogonal projection matrix.
+	_projectionMatrix[ 0] =  2.0f / texWidth;
+	_projectionMatrix[ 1] =  0.0f;
+	_projectionMatrix[ 2] =  0.0f;
+	_projectionMatrix[ 3] =  0.0f;
+
+	_projectionMatrix[ 4] =  0.0f;
+	_projectionMatrix[ 5] =  2.0f / texHeight;
+	_projectionMatrix[ 6] =  0.0f;
+	_projectionMatrix[ 7] =  0.0f;
+
+	_projectionMatrix[ 8] =  0.0f;
+	_projectionMatrix[ 9] =  0.0f;
+	_projectionMatrix[10] =  0.0f;
+	_projectionMatrix[11] =  0.0f;
+
+	_projectionMatrix[12] = -1.0f;
+	_projectionMatrix[13] = -1.0f;
+	_projectionMatrix[14] =  0.0f;
+	_projectionMatrix[15] =  1.0f;
+
+	// Directly apply changes when we are active.
+	if (isActive()) {
+		applyViewport();
+	}
+}
+#endif // !USE_FORCED_GLES
+
+} // End of namespace OpenGL
diff --git a/backends/graphics/opengl/framebuffer.h b/backends/graphics/opengl/framebuffer.h
new file mode 100644
index 0000000000..be829de3d2
--- /dev/null
+++ b/backends/graphics/opengl/framebuffer.h
@@ -0,0 +1,157 @@
+/* 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_FRAMEBUFFER_H
+#define BACKENDS_GRAPHICS_OPENGL_FRAMEBUFFER_H
+
+#include "backends/graphics/opengl/opengl-sys.h"
+
+namespace OpenGL {
+
+/**
+ * Object describing a framebuffer OpenGL can render to.
+ */
+class Framebuffer {
+public:
+	Framebuffer();
+	virtual ~Framebuffer() {};
+
+	/**
+	 * Activate framebuffer.
+	 *
+	 * This is supposed to set all state associated with the framebuffer.
+	 */
+	virtual void activate() = 0;
+
+	/**
+	 * Deactivate framebuffer.
+	 *
+	 * This is supposed to make any cleanup required when unbinding the
+	 * framebuffer.
+	 */
+	virtual void deactivate();
+
+	/**
+	 * Set the clear color of the framebuffer.
+	 */
+	void setClearColor(GLfloat r, GLfloat g, GLfloat b, GLfloat a);
+
+	/**
+	 * Enable/disable GL_BLEND.
+	 */
+	void enableBlend(bool enable);
+
+	/**
+	 * Enable/disable GL_SCISSOR_TEST.
+	 */
+	void enableScissorTest(bool enable);
+
+	/**
+	 * Set scissor box dimensions.
+	 */
+	void setScissorBox(GLint x, GLint y, GLsizei w, GLsizei h);
+
+	/**
+	 * Obtain projection matrix of the framebuffer.
+	 */
+	const GLfloat *getProjectionMatrix() const { return _projectionMatrix; }
+protected:
+	bool isActive() const { return _isActive; }
+
+	GLint _viewport[4];
+	void applyViewport();
+
+	GLfloat _projectionMatrix[4*4];
+private:
+	bool _isActive;
+
+	GLfloat _clearColor[4];
+	void applyClearColor();
+
+	bool _blendState;
+	void applyBlendState();
+
+	bool _scissorTestState;
+	void applyScissorTestState();
+
+	GLint _scissorBox[4];
+	void applyScissorBox();
+};
+
+/**
+ * Default back buffer implementation.
+ */
+class Backbuffer : public Framebuffer {
+public:
+	virtual void activate();
+
+	/**
+	 * Set the dimensions (a.k.a. size) of the back buffer.
+	 */
+	void setDimensions(uint width, uint height);
+};
+
+#if !USE_FORCED_GLES
+class GLTexture;
+
+/**
+ * Render to texture framebuffer implementation.
+ *
+ * This target allows to render to a texture, which can then be used for
+ * further rendering.
+ */
+class TextureTarget : public Framebuffer {
+public:
+	TextureTarget();
+	virtual ~TextureTarget();
+
+	virtual void activate();
+
+	/**
+	 * Notify that the GL context is about to be destroyed.
+	 */
+	void destroy();
+
+	/**
+	 * Notify that the GL context has been created.
+	 */
+	void create();
+
+	/**
+	 * Set size of the texture target.
+	 */
+	void setSize(uint width, uint height);
+
+	/**
+	 * Query pointer to underlying GL texture.
+	 */
+	GLTexture *getTexture() const { return _texture; }
+private:
+	GLTexture *_texture;
+	GLuint _glFBO;
+	bool _needUpdate;
+};
+#endif
+
+} // End of namespace OpenGL
+
+#endif
diff --git a/backends/graphics/opengl/opengl-graphics.cpp b/backends/graphics/opengl/opengl-graphics.cpp
index a8301482d3..36fc7b88aa 100644
--- a/backends/graphics/opengl/opengl-graphics.cpp
+++ b/backends/graphics/opengl/opengl-graphics.cpp
@@ -57,9 +57,6 @@ OpenGLGraphicsManager::OpenGLGraphicsManager()
 #ifdef USE_OSD
       , _osdAlpha(0), _osdFadeStartTime(0), _osd(nullptr)
 #endif
-#if !USE_FORCED_GLES
-      , _projectionMatrix()
-#endif
     {
 	memset(_gamePalette, 0, sizeof(_gamePalette));
 	g_context.reset();
@@ -379,9 +376,9 @@ void OpenGLGraphicsManager::updateScreen() {
 		// cleared. For example, when switching from overlay visible to
 		// invisible, we need to assure that all contents are cleared to
 		// properly remove all overlay contents.
-		GL_CALL(glDisable(GL_SCISSOR_TEST));
+		_backBuffer.enableScissorTest(false);
 		GL_CALL(glClear(GL_COLOR_BUFFER_BIT));
-		GL_CALL(glEnable(GL_SCISSOR_TEST));
+		_backBuffer.enableScissorTest(true);
 
 		--_scissorOverride;
 	} else {
@@ -475,7 +472,7 @@ void OpenGLGraphicsManager::showOverlay() {
 	_forceRedraw = true;
 
 	// Allow drawing inside full screen area.
-	GL_CALL(glDisable(GL_SCISSOR_TEST));
+	_backBuffer.enableScissorTest(false);
 
 	// Update cursor position.
 	setMousePosition(_cursorX, _cursorY);
@@ -486,7 +483,7 @@ void OpenGLGraphicsManager::hideOverlay() {
 	_forceRedraw = true;
 
 	// Limit drawing to screen area.
-	GL_CALL(glEnable(GL_SCISSOR_TEST));
+	_backBuffer.enableScissorTest(true);
 	_scissorOverride = 3;
 
 	// Update cursor position.
@@ -763,23 +760,15 @@ void OpenGLGraphicsManager::setActualScreenSize(uint width, uint height) {
 	_outputScreenWidth = width;
 	_outputScreenHeight = height;
 
-	// Setup coordinate system.
-	GL_CALL(glViewport(0, 0, _outputScreenWidth, _outputScreenHeight));
-
-	// Orthogonal projection matrix in column major order.
-	const GLfloat orthoProjection[4*4] = {
-		 2.0f / _outputScreenWidth,  0.0f                      ,  0.0f, 0.0f,
-		 0.0f                     , -2.0f / _outputScreenHeight,  0.0f, 0.0f,
-		 0.0f                     ,  0.0f                      , -1.0f, 0.0f,
-		-1.0f                     ,  1.0f                      ,  0.0f, 1.0f
-	};
+	// Setup backbuffer size.
+	_backBuffer.setDimensions(width, height);
 
 #if !USE_FORCED_GL && !USE_FORCED_GLES && !USE_FORCED_GLES2
 	if (!g_context.shadersSupported) {
 #endif
 #if !USE_FORCED_GLES2
 		GL_CALL(glMatrixMode(GL_PROJECTION));
-		GL_CALL(glLoadMatrixf(orthoProjection));
+		GL_CALL(glLoadMatrixf(_backBuffer.getProjectionMatrix()));
 
 		GL_CALL(glMatrixMode(GL_MODELVIEW));
 		GL_CALL(glLoadIdentity());
@@ -788,9 +777,7 @@ void OpenGLGraphicsManager::setActualScreenSize(uint width, uint height) {
 	} else {
 #endif
 #if !USE_FORCED_GLES
-		assert(sizeof(_projectionMatrix) == sizeof(orthoProjection));
-		memcpy(_projectionMatrix, orthoProjection, sizeof(_projectionMatrix));
-		ShaderMan.query(ShaderManager::kDefault)->activate(_projectionMatrix);
+		ShaderMan.query(ShaderManager::kDefault)->activate(_backBuffer.getProjectionMatrix());
 #endif
 #if !USE_FORCED_GL && !USE_FORCED_GLES && !USE_FORCED_GLES2
 	}
@@ -890,20 +877,21 @@ void OpenGLGraphicsManager::notifyContextCreate(const Graphics::PixelFormat &def
 	GL_CALL(glDisable(GL_DEPTH_TEST));
 	GL_CALL(glDisable(GL_DITHER));
 
-	// Default to black as clear color.
-	GL_CALL(glClearColor(0.0f, 0.0f, 0.0f, 0.0f));
 	g_context.activePipeline->setColor(1.0f, 1.0f, 1.0f, 1.0f);
 
-	// Setup alpha blend (for overlay and cursor).
-	GL_CALL(glEnable(GL_BLEND));
 	GL_CALL(glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA));
 
+	// Setup backbuffer state.
+
+	// Default to black as clear color.
+	_backBuffer.setClearColor(0.0f, 0.0f, 0.0f, 0.0f);
+	// Setup alpha blend (for overlay and cursor).
+	_backBuffer.enableBlend(true);
 	// Setup scissor state accordingly.
-	if (_overlayVisible) {
-		GL_CALL(glDisable(GL_SCISSOR_TEST));
-	} else {
-		GL_CALL(glEnable(GL_SCISSOR_TEST));
-	}
+	_backBuffer.enableScissorTest(!_overlayVisible);
+
+	g_context.setFramebuffer(&_backBuffer);
+
 	// Clear the whole screen for the first three frames to assure any
 	// leftovers are cleared.
 	_scissorOverride = 3;
@@ -916,7 +904,7 @@ void OpenGLGraphicsManager::notifyContextCreate(const Graphics::PixelFormat &def
 #if !USE_FORCED_GLES
 	if (g_context.shadersSupported) {
 		ShaderMan.notifyCreate();
-		ShaderMan.query(ShaderManager::kDefault)->activate(_projectionMatrix);
+		ShaderMan.query(ShaderManager::kDefault)->activate(_backBuffer.getProjectionMatrix());
 	}
 #endif
 
@@ -975,6 +963,9 @@ void OpenGLGraphicsManager::notifyContextDestroy() {
 	}
 #endif
 
+	// Unset back buffer.
+	g_context.setFramebuffer(nullptr);
+
 	// Destroy rendering pipeline.
 	g_context.setPipeline(nullptr);
 	delete _pipeline;
@@ -1185,10 +1176,10 @@ void OpenGLGraphicsManager::recalculateDisplayArea() {
 	// Setup drawing limitation for game graphics.
 	// This invovles some trickery because OpenGL's viewport coordinate system
 	// is upside down compared to ours.
-	GL_CALL(glScissor(_displayX,
-	                 _outputScreenHeight - _displayHeight - _displayY,
-	                 _displayWidth,
-	                 _displayHeight));
+	_backBuffer.setScissorBox(_displayX,
+	                          _outputScreenHeight - _displayHeight - _displayY,
+	                          _displayWidth,
+	                          _displayHeight);
 	// Clear the whole screen for the first three frames to remove leftovers.
 	_scissorOverride = 3;
 
diff --git a/backends/graphics/opengl/opengl-graphics.h b/backends/graphics/opengl/opengl-graphics.h
index f3cd4c437f..35435c156e 100644
--- a/backends/graphics/opengl/opengl-graphics.h
+++ b/backends/graphics/opengl/opengl-graphics.h
@@ -24,6 +24,7 @@
 #define BACKENDS_GRAPHICS_OPENGL_OPENGL_GRAPHICS_H
 
 #include "backends/graphics/opengl/opengl-sys.h"
+#include "backends/graphics/opengl/framebuffer.h"
 #include "backends/graphics/graphics.h"
 
 #include "common/frac.h"
@@ -305,6 +306,11 @@ private:
 	void initializeGLContext();
 
 	/**
+	 * Render back buffer.
+	 */
+	Backbuffer _backBuffer;
+
+	/**
 	 * OpenGL pipeline used for rendering.
 	 */
 	Pipeline *_pipeline;
@@ -527,17 +533,6 @@ private:
 	 */
 	uint _scissorOverride;
 
-#if !USE_FORCED_GLES
-	//
-	// Shaders
-	//
-
-	/**
-	 * Projection matrix used.
-	 */
-	GLfloat _projectionMatrix[4*4];
-#endif
-
 #ifdef USE_OSD
 	//
 	// OSD
diff --git a/backends/graphics/opengl/opengl-sys.h b/backends/graphics/opengl/opengl-sys.h
index f68897ba58..ffc80a23dc 100644
--- a/backends/graphics/opengl/opengl-sys.h
+++ b/backends/graphics/opengl/opengl-sys.h
@@ -88,6 +88,7 @@ enum ContextType {
 };
 
 class Pipeline;
+class Framebuffer;
 
 /**
  * Description structure of the OpenGL (ES) context.
@@ -123,6 +124,19 @@ struct Context {
 #include "backends/graphics/opengl/opengl-func.h"
 #undef GL_FUNC_DEF
 
+	/** Currently active framebuffer. */
+	Framebuffer *activeFramebuffer;
+
+	/**
+	 * Set new framebuffer.
+	 *
+	 * Client is responsible for any memory management related to framebuffers.
+	 *
+	 * @param framebuffer Framebuffer to activate.
+	 * @return Formerly active framebuffer.
+	 */
+	Framebuffer *setFramebuffer(Framebuffer *framebuffer);
+
 	//
 	// Wrapper functionality to handle fixed-function pipelines and
 	// programmable pipelines in the same fashion.
diff --git a/backends/graphics/opengl/texture.cpp b/backends/graphics/opengl/texture.cpp
index 828dade0be..02e1b2c325 100644
--- a/backends/graphics/opengl/texture.cpp
+++ b/backends/graphics/opengl/texture.cpp
@@ -23,6 +23,7 @@
 #include "backends/graphics/opengl/texture.h"
 #include "backends/graphics/opengl/shader.h"
 #include "backends/graphics/opengl/pipeline.h"
+#include "backends/graphics/opengl/framebuffer.h"
 
 #include "common/rect.h"
 #include "common/textconsole.h"
@@ -515,38 +516,30 @@ void TextureRGB555::updateTexture() {
 TextureCLUT8GPU::TextureCLUT8GPU()
     : _clut8Texture(GL_ALPHA, GL_ALPHA, GL_UNSIGNED_BYTE),
       _paletteTexture(GL_RGBA, GL_RGBA, GL_UNSIGNED_BYTE),
-      _glTexture(GL_RGBA, GL_RGBA, GL_UNSIGNED_BYTE),
-      _glFBO(0), _clut8Vertices(), _projectionMatrix(),
-      _paletteLocation(-1),
+      _target(new TextureTarget()), _clut8Vertices(), _paletteLocation(-1),
       _clut8Data(), _userPixelData(), _palette(), _paletteDirty(false) {
 	// Allocate space for 256 colors.
 	_paletteTexture.setSize(256, 1);
 
 	_paletteLocation = ShaderMan.query(ShaderManager::kCLUT8LookUp)->getUniformLocation("palette");
-
-	setupFBO();
 }
 
 TextureCLUT8GPU::~TextureCLUT8GPU() {
-	GL_CALL_SAFE(glDeleteFramebuffers, (1, &_glFBO));
+	delete _target;
 	_clut8Data.free();
 }
 
 void TextureCLUT8GPU::destroy() {
 	_clut8Texture.destroy();
 	_paletteTexture.destroy();
-	_glTexture.destroy();
-
-	GL_CALL(glDeleteFramebuffers(1, &_glFBO));
-	_glFBO = 0;
+	_target->destroy();
 }
 
 void TextureCLUT8GPU::recreate() {
 	_clut8Texture.create();
 	_paletteTexture.create();
-	_glTexture.create();
 	_paletteLocation = ShaderMan.query(ShaderManager::kCLUT8LookUp)->getUniformLocation("palette");
-	setupFBO();
+	_target->create();
 
 	// In case image date exists assure it will be completely refreshed next
 	// time.
@@ -557,13 +550,13 @@ void TextureCLUT8GPU::recreate() {
 }
 
 void TextureCLUT8GPU::enableLinearFiltering(bool enable) {
-	_glTexture.enableLinearFiltering(enable);
+	_target->getTexture()->enableLinearFiltering(enable);
 }
 
 void TextureCLUT8GPU::allocate(uint width, uint height) {
 	// Assure the texture can contain our user data.
 	_clut8Texture.setSize(width, height);
-	_glTexture.setSize(width, height);
+	_target->setSize(width, height);
 
 	// In case the needed texture dimension changed we will reinitialize the
 	// texture data buffer.
@@ -587,26 +580,6 @@ void TextureCLUT8GPU::allocate(uint width, uint height) {
 
 	_clut8Vertices[6] = width;
 	_clut8Vertices[7] = height;
-
-	_projectionMatrix[ 0] =  2.0f / _glTexture.getWidth();
-	_projectionMatrix[ 1] =  0.0f;
-	_projectionMatrix[ 2] =  0.0f;
-	_projectionMatrix[ 3] =  0.0f;
-
-	_projectionMatrix[ 4] =  0.0f;
-	_projectionMatrix[ 5] =  2.0f / _glTexture.getHeight();
-	_projectionMatrix[ 6] =  0.0f;
-	_projectionMatrix[ 7] =  0.0f;
-
-	_projectionMatrix[ 8] =  0.0f;
-	_projectionMatrix[ 9] =  0.0f;
-	_projectionMatrix[10] =  0.0f;
-	_projectionMatrix[11] =  0.0f;
-
-	_projectionMatrix[12] = -1.0f;
-	_projectionMatrix[13] = -1.0f;
-	_projectionMatrix[14] =  0.0f;
-	_projectionMatrix[15] =  1.0f;
 }
 
 void TextureCLUT8GPU::draw(GLfloat x, GLfloat y, GLfloat w, GLfloat h) {
@@ -619,7 +592,7 @@ void TextureCLUT8GPU::draw(GLfloat x, GLfloat y, GLfloat w, GLfloat h) {
 	updateTextures();
 
 	// Set the texture.
-	_glTexture.bind();
+	_target->getTexture()->bind();
 
 	// Calculate the screen rect where the texture will be drawn.
 	const GLfloat vertices[4*2] = {
@@ -630,7 +603,7 @@ void TextureCLUT8GPU::draw(GLfloat x, GLfloat y, GLfloat w, GLfloat h) {
 	};
 
 	// Setup coordinates for drawing.
-	g_context.activePipeline->setDrawCoordinates(vertices, _glTexture.getTexCoords());
+	g_context.activePipeline->setDrawCoordinates(vertices, _target->getTexture()->getTexCoords());
 
 	// Draw the texture to the screen buffer.
 	GL_CALL(glDrawArrays(GL_TRIANGLE_STRIP, 0, 4));
@@ -695,24 +668,7 @@ void TextureCLUT8GPU::lookUpColors() {
 	GLint oldProgram = 0;
 	GL_CALL(glGetIntegerv(GL_CURRENT_PROGRAM, &oldProgram));
 
-	GLint viewport[4];
-	GL_CALL(glGetIntegerv(GL_VIEWPORT, viewport));
-
-	GLboolean scissorState;
-	GL_ASSIGN(scissorState, glIsEnabled(GL_SCISSOR_TEST));
-	GLboolean blendState;
-	GL_ASSIGN(blendState, glIsEnabled(GL_BLEND));
-
-	GLint oldFBO = 0;
-	GL_CALL(glGetIntegerv(GL_FRAMEBUFFER_BINDING, &oldFBO));
-
-	// Update state.
-	GL_CALL(glViewport(0, 0, _glTexture.getWidth(), _glTexture.getHeight()));
-	GL_CALL(glDisable(GL_SCISSOR_TEST));
-	GL_CALL(glDisable(GL_BLEND));
-
-	// Bind framebuffer.
-	GL_CALL(glBindFramebuffer(GL_FRAMEBUFFER, _glFBO));
+	Framebuffer *oldFramebuffer = g_context.setFramebuffer(_target);
 
 	// Set the palette texture.
 	GL_CALL(glActiveTexture(GL_TEXTURE1));
@@ -724,40 +680,15 @@ void TextureCLUT8GPU::lookUpColors() {
 
 	// Do color look up.
 	Shader *lookUpShader = ShaderMan.query(ShaderManager::kCLUT8LookUp);
-	lookUpShader->activate(_projectionMatrix);
+	lookUpShader->activate(_target->getProjectionMatrix());
 	lookUpShader->setUniformI(_paletteLocation, 1);
 	g_context.activePipeline->setDrawCoordinates(_clut8Vertices, _clut8Texture.getTexCoords());
 	GL_CALL(glDrawArrays(GL_TRIANGLE_STRIP, 0, 4));
 
 	// Restore old state.
-	GL_CALL(glUseProgram(oldProgram));
-	GL_CALL(glBindFramebuffer(GL_FRAMEBUFFER, oldFBO));
+	g_context.setFramebuffer(oldFramebuffer);
 
-	if (blendState) {
-		GL_CALL(glEnable(GL_BLEND));
-	}
-	if (scissorState) {
-		GL_CALL(glEnable(GL_SCISSOR_TEST));
-	}
-	GL_CALL(glViewport(viewport[0], viewport[1], viewport[2], viewport[3]));
-}
-
-void TextureCLUT8GPU::setupFBO() {
-	// Allocate framebuffer object if necessary.
-	if (!_glFBO) {
-		GL_CALL(glGenFramebuffers(1, &_glFBO));
-	}
-
-	// Save old FBO.
-	GLint oldFBO = 0;
-	GL_CALL(glGetIntegerv(GL_FRAMEBUFFER_BINDING, &oldFBO));
-
-	// Attach destination texture to FBO.
-	GL_CALL(glBindFramebuffer(GL_FRAMEBUFFER, _glFBO));
-	GL_CALL(glFramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, _glTexture.getGLTexture(), 0));
-
-	// Restore old FBO.
-	GL_CALL(glBindFramebuffer(GL_FRAMEBUFFER, oldFBO));
+	GL_CALL(glUseProgram(oldProgram));
 }
 #endif // !USE_FORCED_GLES
 
diff --git a/backends/graphics/opengl/texture.h b/backends/graphics/opengl/texture.h
index 5f586f6a2f..df9893fa70 100644
--- a/backends/graphics/opengl/texture.h
+++ b/backends/graphics/opengl/texture.h
@@ -318,6 +318,8 @@ private:
 #endif // !USE_FORCED_GL
 
 #if !USE_FORCED_GLES
+class TextureTarget;
+
 class TextureCLUT8GPU : public Surface {
 public:
 	TextureCLUT8GPU();
@@ -359,12 +361,10 @@ private:
 
 	GLTexture _clut8Texture;
 	GLTexture _paletteTexture;
-	GLTexture _glTexture;
 
-	void setupFBO();
-	GLuint _glFBO;
+	TextureTarget *_target;
+
 	GLfloat _clut8Vertices[4*2];
-	GLfloat _projectionMatrix[4*4];
 
 	GLint _paletteLocation;
 
diff --git a/backends/module.mk b/backends/module.mk
index 305942279a..f786933ade 100644
--- a/backends/module.mk
+++ b/backends/module.mk
@@ -54,6 +54,7 @@ ifdef USE_OPENGL
 MODULE_OBJS += \
 	graphics/opengl/context.o \
 	graphics/opengl/debug.o \
+	graphics/opengl/framebuffer.o \
 	graphics/opengl/opengl-graphics.o \
 	graphics/opengl/pipeline.o \
 	graphics/opengl/shader.o \