5 files changed, 65 insertions, 13 deletions
diff --git a/backends/graphics/opengl/context.cpp b/backends/graphics/opengl/context.cpp
index c4869c2ae6..d1776f851d 100644
--- a/backends/graphics/opengl/context.cpp
+++ b/backends/graphics/opengl/context.cpp
@@ -28,15 +28,23 @@
 namespace OpenGL {
 
 void Context::reset() {
+	ready = false;
+	type = kContextGL;
 	NPOTSupported = false;
 }
 
 Context g_context;
 
-void OpenGLGraphicsManager::initializeGLContext() {
+void OpenGLGraphicsManager::initializeGLContext(ContextType type) {
 	// Initialize default state.
 	g_context.reset();
 
+#if USE_FORCED_GL
+	type = kContextGL;
+#elif USE_FORCED_GLES
+	type = kContextGLES;
+#endif
+
 	// Load all functions.
 	// We use horrible trickery to silence C++ compilers.
 	// See backends/plugins/sdl/sdl-provider.cpp for more information.
@@ -64,6 +72,9 @@ void OpenGLGraphicsManager::initializeGLContext() {
 			g_context.NPOTSupported = true;
 		}
 	}
+
+	g_context.ready = true;
+	g_context.type = type;
 }
 
 } // End of namespace OpenGL
diff --git a/backends/graphics/opengl/opengl-func.h b/backends/graphics/opengl/opengl-func.h
index 75bc0b4e81..0ff39c845a 100644
--- a/backends/graphics/opengl/opengl-func.h
+++ b/backends/graphics/opengl/opengl-func.h
@@ -70,9 +70,10 @@ GL_FUNC_DEF(void, glColor4f, (GLfloat red, GLfloat green, GLfloat blue, GLfloat
 GL_FUNC_DEF(void, glViewport, (GLint x, GLint y, GLsizei width, GLsizei height));
 GL_FUNC_DEF(void, glMatrixMode, (GLenum mode));
 GL_FUNC_DEF(void, glLoadIdentity, ());
-#ifdef USE_GLES
+#if !USE_FORCED_GL
 GL_FUNC_DEF(void, glOrthof, (GLfloat left, GLfloat right, GLfloat bottom, GLfloat top, GLfloat zNear, GLfloat zFar));
-#else
+#endif
+#if !USE_FORCED_GLES
 GL_FUNC_DEF(void, glOrtho, (GLdouble left, GLdouble right, GLdouble bottom, GLdouble top, GLdouble near_val, GLdouble far_val));
 #endif
 GL_FUNC_DEF(void, glShadeModel, (GLenum mode));
diff --git a/backends/graphics/opengl/opengl-graphics.cpp b/backends/graphics/opengl/opengl-graphics.cpp
index 1024ee546e..78ae27d8a6 100644
--- a/backends/graphics/opengl/opengl-graphics.cpp
+++ b/backends/graphics/opengl/opengl-graphics.cpp
@@ -759,10 +759,16 @@ void OpenGLGraphicsManager::setActualScreenSize(uint width, uint height) {
 
 	GL_CALL(glMatrixMode(GL_PROJECTION));
 	GL_CALL(glLoadIdentity());
-#ifdef USE_GLES
+#if   USE_FORCED_GLES
 	GL_CALL(glOrthof(0, _outputScreenWidth, _outputScreenHeight, 0, -1, 1));
-#else
+#elif USE_FORCED_GL
 	GL_CALL(glOrtho(0, _outputScreenWidth, _outputScreenHeight, 0, -1, 1));
+#else
+	if (isGLESContext()) {
+		GL_CALL(glOrthof(0, _outputScreenWidth, _outputScreenHeight, 0, -1, 1));
+	} else {
+		GL_CALL(glOrtho(0, _outputScreenWidth, _outputScreenHeight, 0, -1, 1));
+	}
 #endif
 	GL_CALL(glMatrixMode(GL_MODELVIEW));
 	GL_CALL(glLoadIdentity());
@@ -834,9 +840,9 @@ void OpenGLGraphicsManager::setActualScreenSize(uint width, uint height) {
 	++_screenChangeID;
 }
 
-void OpenGLGraphicsManager::notifyContextCreate(const Graphics::PixelFormat &defaultFormat, const Graphics::PixelFormat &defaultFormatAlpha) {
+void OpenGLGraphicsManager::notifyContextCreate(const Graphics::PixelFormat &defaultFormat, const Graphics::PixelFormat &defaultFormatAlpha, ContextType type) {
 	// Initialize context for use.
-	initializeGLContext();
+	initializeGLContext(type);
 
 	// Disable 3D properties.
 	GL_CALL(glDisable(GL_CULL_FACE));
@@ -1014,7 +1020,11 @@ bool OpenGLGraphicsManager::getGLPixelFormat(const Graphics::PixelFormat &pixelF
 		glFormat = GL_RGBA;
 		glType = GL_UNSIGNED_SHORT_4_4_4_4;
 		return true;
-#ifndef USE_GLES
+#if !USE_FORCED_GLES
+	// The formats below are not supported by every GLES implementation.
+	// Thus, we do not mark them as supported when a GLES context is setup.
+	} else if (isGLESContext()) {
+		return false;
 #ifdef SCUMM_LITTLE_ENDIAN
 	} else if (pixelFormat == Graphics::PixelFormat(4, 8, 8, 8, 8, 24, 16, 8, 0)) { // RGBA8888
 		glIntFormat = GL_RGBA;
@@ -1023,8 +1033,6 @@ bool OpenGLGraphicsManager::getGLPixelFormat(const Graphics::PixelFormat &pixelF
 		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.
 		glIntFormat = GL_RGB;
 		glFormat = GL_BGRA;
 		glType = GL_UNSIGNED_SHORT_1_5_5_5_REV;
@@ -1066,7 +1074,7 @@ bool OpenGLGraphicsManager::getGLPixelFormat(const Graphics::PixelFormat &pixelF
 		glFormat = GL_BGRA;
 		glType = GL_UNSIGNED_SHORT_4_4_4_4;
 		return true;
-#endif
+#endif // !USE_FORCED_GLES
 	} else {
 		return false;
 	}
diff --git a/backends/graphics/opengl/opengl-graphics.h b/backends/graphics/opengl/opengl-graphics.h
index 3d5f74b387..5f0436c0b5 100644
--- a/backends/graphics/opengl/opengl-graphics.h
+++ b/backends/graphics/opengl/opengl-graphics.h
@@ -117,6 +117,16 @@ public:
 
 protected:
 	/**
+	 * Whether an OpenGL (context) is active.
+	 */
+	bool isInitialized() const { return g_context.ready; }
+
+	/**
+	 * Whether an GLES context is active.
+	 */
+	bool isGLESContext() const { return g_context.type == kContextGLES; }
+
+	/**
 	 * Set up the actual screen size available for the OpenGL code to do any
 	 * drawing.
 	 *
@@ -133,8 +143,9 @@ protected:
 	 *                           (this is used for the CLUT8 game screens).
 	 * @param defaultFormatAlpha The new default format with an alpha channel
 	 *                           (this is used for the overlay and cursor).
+	 * @param type               Type of the created context.
 	 */
-	void notifyContextCreate(const Graphics::PixelFormat &defaultFormat, const Graphics::PixelFormat &defaultFormatAlpha);
+	void notifyContextCreate(const Graphics::PixelFormat &defaultFormat, const Graphics::PixelFormat &defaultFormatAlpha, ContextType type);
 
 	/**
 	 * Notify the manager that the OpenGL context is about to be destroyed.
@@ -282,8 +293,10 @@ private:
 
 	/**
 	 * Initialize the active context for use.
+	 *
+	 * @param type Type of the context to initialize.
 	 */
-	void initializeGLContext();
+	void initializeGLContext(ContextType type);
 
 protected:
 	/**
diff --git a/backends/graphics/opengl/opengl-sys.h b/backends/graphics/opengl/opengl-sys.h
index f78b3377b3..550dbb44c5 100644
--- a/backends/graphics/opengl/opengl-sys.h
+++ b/backends/graphics/opengl/opengl-sys.h
@@ -30,6 +30,14 @@
 #include "backends/platform/sdl/sdl-sys.h"
 #endif
 
+// We allow to force GL or GLES modes on compile time.
+// For this the USE_GLES_MODE define is used. The following values represent
+// the given selection choices:
+//  0 - Force OpenGL context
+//  1 - Force OpenGL ES context
+#define USE_FORCED_GL   (defined(USE_GLES_MODE) && USE_GLES_MODE == 0)
+#define USE_FORCED_GLES (defined(USE_GLES_MODE) && USE_GLES_MODE == 1)
+
 // On Tizen we include the toolchain's OpenGL file. This is something we
 // actually want to avoid. However, since Tizen uses eglGetProcAddress which
 // is not required to return valid function pointers to non OpenGL extension
@@ -59,10 +67,21 @@
 
 namespace OpenGL {
 
+enum ContextType {
+	kContextGL,
+	kContextGLES
+};
+
 /**
  * Description structure of the OpenGL (ES) context.
  */
 struct Context {
+	/** Whether the context is properly initalized or not. */
+	bool ready;
+
+	/** The type of the active context. */
+	ContextType type;
+
 	/**
 	 * Reset context.
 	 *