OPENGL: Add support for shaders with GL contexts.

9 files changed, 358 insertions, 54 deletions

diff --git a/backends/graphics/opengl/context.cpp b/backends/graphics/opengl/context.cpp
index 764cabcbde..618be07a57 100644
--- a/backends/graphics/opengl/context.cpp
+++ b/backends/graphics/opengl/context.cpp
@@ -74,14 +74,35 @@ void OpenGLGraphicsManager::initializeGLContext() {
 
 	const char *extString = (const char *)g_context.glGetString(GL_EXTENSIONS);
 
+#if !USE_FORCED_GLES && !USE_FORCED_GLES2
+	bool ARBShaderObjects = false;
+	bool ARBShadingLanguage100 = false;
+	bool ARBVertexShader = false;
+	bool ARBFragmentShader = false;
+#endif
+
 	Common::StringTokenizer tokenizer(extString, " ");
 	while (!tokenizer.empty()) {
 		Common::String token = tokenizer.nextToken();
 
 		if (token == "GL_ARB_texture_non_power_of_two") {
 			g_context.NPOTSupported = true;
+#if !USE_FORCED_GLES && !USE_FORCED_GLES2
+		} else if (token == "GL_ARB_shader_objects") {
+			ARBShaderObjects = true;
+		} else if (token == "GL_ARB_shading_language_100") {
+			ARBShadingLanguage100 = true;
+		} else if (token == "GL_ARB_vertex_shader") {
+			ARBVertexShader = true;
+		} else if (token == "GL_ARB_fragment_shader") {
+			ARBFragmentShader = true;
+#endif
 		}
 	}
+
+#if !USE_FORCED_GLES && !USE_FORCED_GLES2
+	g_context.shadersSupported = ARBShaderObjects & ARBShadingLanguage100 & ARBVertexShader & ARBFragmentShader;
+#endif
 }
 
 } // End of namespace OpenGL
diff --git a/backends/graphics/opengl/opengl-defs.h b/backends/graphics/opengl/opengl-defs.h
index fe79caadd4..edcf334a0b 100644
--- a/backends/graphics/opengl/opengl-defs.h
+++ b/backends/graphics/opengl/opengl-defs.h
@@ -76,6 +76,12 @@ typedef float  GLclampf; /* single precision float in [0,1] */
 typedef double GLdouble; /* double precision float */
 typedef double GLclampd; /* double precision float in [0,1] */
 typedef char   GLchar;
+typedef GLchar GLcharARB;
+#if defined(__APPLE__) || defined(MACOSX)
+typedef void  *GLhandleARB;
+#else
+typedef uint   GLhandleARB;
+#endif
 
 /*
  * Constants
@@ -223,13 +229,20 @@ typedef char   GLchar;
 
 /* Shaders */
 #define GL_FRAGMENT_SHADER                0x8B30
+#define GL_FRAGMENT_SHADER_ARB            0x8B30
+
 #define GL_VERTEX_SHADER                  0x8B31
+#define GL_VERTEX_SHADER_ARB              0x8B31
 
 /* Programs */
 #define GL_COMPILE_STATUS                 0x8B81
 #define GL_LINK_STATUS                    0x8B82
 #define GL_INFO_LOG_LENGTH                0x8B84
 
+#define GL_OBJECT_COMPILE_STATUS_ARB      0x8B81
+#define GL_OBJECT_LINK_STATUS_ARB         0x8B82
+#define GL_OBJECT_INFO_LOG_LENGTH_ARB     0x8B84
+
 /* Textures */
 #define GL_TEXTURE0                       0x84C0
 
diff --git a/backends/graphics/opengl/opengl-func.h b/backends/graphics/opengl/opengl-func.h
index 633385a4d0..d022d00b30 100644
--- a/backends/graphics/opengl/opengl-func.h
+++ b/backends/graphics/opengl/opengl-func.h
@@ -116,3 +116,24 @@ GL_FUNC_DEF(void, glGetShaderInfoLog, (GLuint shader, GLsizei bufSize, GLsizei *
 GL_FUNC_DEF(void, glEnableVertexAttribArray, (GLuint index));
 GL_FUNC_DEF(void, glActiveTexture, (GLenum texture));
 #endif
+
+#if !USE_FORCED_GLES && !USE_FORCED_GLES2
+GL_EXT_FUNC_DEF(void, glDeleteObjectARB, (GLhandleARB obj));
+GL_EXT_FUNC_DEF(GLhandleARB, glCreateProgramObjectARB, ());
+GL_EXT_FUNC_DEF(void, glAttachObjectARB, (GLhandleARB containerObj, GLhandleARB obj));
+GL_EXT_FUNC_DEF(void, glBindAttribLocationARB, (GLhandleARB programObj, GLuint index, const GLcharARB *name));
+GL_EXT_FUNC_DEF(void, glLinkProgramARB, (GLhandleARB programObj));
+GL_EXT_FUNC_DEF(void, glDetachObjectARB, (GLhandleARB containerObj, GLhandleARB attachedObj));
+GL_EXT_FUNC_DEF(void, glGetObjectParameterivARB, (GLhandleARB obj, GLenum pname, GLint *params));
+GL_EXT_FUNC_DEF(GLint, glGetUniformLocationARB, (GLhandleARB programObj, const GLcharARB *name));
+GL_EXT_FUNC_DEF(void, glGetInfoLogARB, (GLhandleARB obj, GLsizei maxLength, GLsizei *length, GLcharARB *infoLog));
+GL_EXT_FUNC_DEF(void, glUseProgramObjectARB, (GLhandleARB programObj));
+GL_EXT_FUNC_DEF(void, glUniformMatrix4fvARB, (GLint location, GLsizei count, GLboolean transpose, const GLfloat *value));
+GL_EXT_FUNC_DEF(void, glUniform1iARB, (GLint location, GLint v0));
+GL_EXT_FUNC_DEF(GLhandleARB, glCreateShaderObjectARB, (GLenum shaderType));
+GL_EXT_FUNC_DEF(void, glShaderSourceARB, (GLhandleARB shaderObj, GLsizei count, const GLcharARB **string, const GLint *length));
+GL_EXT_FUNC_DEF(void, glCompileShaderARB, (GLhandleARB shaderObj));
+GL_EXT_FUNC_DEF(void, glVertexAttribPointerARB, (GLuint index, GLint size, GLenum type, GLboolean normalized, GLsizei stride, const void *pointer));
+GL_EXT_FUNC_DEF(void, glVertexAttrib4fARB, (GLuint index, GLfloat x, GLfloat y, GLfloat z, GLfloat w));
+GL_EXT_FUNC_DEF(void, glEnableVertexAttribArrayARB, (GLuint index));
+#endif
diff --git a/backends/graphics/opengl/opengl-graphics.cpp b/backends/graphics/opengl/opengl-graphics.cpp
index 7078aa896f..9203390489 100644
--- a/backends/graphics/opengl/opengl-graphics.cpp
+++ b/backends/graphics/opengl/opengl-graphics.cpp
@@ -55,7 +55,7 @@ OpenGLGraphicsManager::OpenGLGraphicsManager()
 #ifdef USE_OSD
       , _osdAlpha(0), _osdFadeStartTime(0), _osd(nullptr)
 #endif
-#if !USE_FORCED_GL && !USE_FORCED_GLES
+#if !USE_FORCED_GLES
       , _shader(nullptr), _projectionMatrix()
 #endif
     {
@@ -70,7 +70,7 @@ OpenGLGraphicsManager::~OpenGLGraphicsManager() {
 #ifdef USE_OSD
 	delete _osd;
 #endif
-#if !USE_FORCED_GL && !USE_FORCED_GLES
+#if !USE_FORCED_GLES
 	delete _shader;
 #endif
 }
@@ -773,7 +773,8 @@ void OpenGLGraphicsManager::setActualScreenSize(uint width, uint height) {
 	};
 
 #if !USE_FORCED_GL && !USE_FORCED_GLES && !USE_FORCED_GLES2
-	if (g_context.type != kContextGLES2) {
+	if (g_context.type == kContextGLES
+	    || (g_context.type == kContextGL && !g_context.shadersSupported)) {
 #endif
 #if !USE_FORCED_GLES2
 		GL_CALL(glMatrixMode(GL_PROJECTION));
@@ -785,7 +786,7 @@ void OpenGLGraphicsManager::setActualScreenSize(uint width, uint height) {
 #if !USE_FORCED_GL && !USE_FORCED_GLES && !USE_FORCED_GLES2
 	} else {
 #endif
-#if !USE_FORCED_GL && !USE_FORCED_GLES
+#if !USE_FORCED_GLES
 		assert(sizeof(_projectionMatrix) == sizeof(orthoProjection));
 		memcpy(_projectionMatrix, orthoProjection, sizeof(_projectionMatrix));
 		if (_shader) {
@@ -894,23 +895,32 @@ void OpenGLGraphicsManager::notifyContextCreate(const Graphics::PixelFormat &def
 	GL_CALL(glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA));
 
 #if !USE_FORCED_GL && !USE_FORCED_GLES && !USE_FORCED_GLES2
-	if (g_context.type != kContextGLES2) {
+	if (g_context.type == kContextGLES2) {
 #endif
-#if !USE_FORCED_GLES2
-		// Enable rendering with vertex and coord arrays.
-		GL_CALL(glEnableClientState(GL_VERTEX_ARRAY));
-		GL_CALL(glEnableClientState(GL_TEXTURE_COORD_ARRAY));
+#if !USE_FORCED_GL && !USE_FORCED_GLES
+		GL_CALL(glEnableVertexAttribArray(kPositionAttribLocation));
+		GL_CALL(glEnableVertexAttribArray(kTexCoordAttribLocation));
 
-		GL_CALL(glEnable(GL_TEXTURE_2D));
+		GL_CALL(glActiveTexture(GL_TEXTURE0));
 #endif
 #if !USE_FORCED_GL && !USE_FORCED_GLES && !USE_FORCED_GLES2
 	} else {
 #endif
-#if !USE_FORCED_GL && !USE_FORCED_GLES
-		GL_CALL(glEnableVertexAttribArray(kPositionAttribLocation));
-		GL_CALL(glEnableVertexAttribArray(kTexCoordAttribLocation));
+#if !USE_FORCED_GLES2
+#if !USE_FORCED_GLES
+		if (g_context.shadersSupported) {
+			GL_CALL(glEnableVertexAttribArrayARB(kPositionAttribLocation));
+			GL_CALL(glEnableVertexAttribArrayARB(kTexCoordAttribLocation));
+		} else {
+#endif
+			// Enable rendering with vertex and coord arrays.
+			GL_CALL(glEnableClientState(GL_VERTEX_ARRAY));
+			GL_CALL(glEnableClientState(GL_TEXTURE_COORD_ARRAY));
+#if !USE_FORCED_GLES
+		}
+#endif
 
-		GL_CALL(glActiveTexture(GL_TEXTURE0));
+		GL_CALL(glEnable(GL_TEXTURE_2D));
 #endif
 #if !USE_FORCED_GL && !USE_FORCED_GLES && !USE_FORCED_GLES2
 	}
@@ -934,19 +944,33 @@ void OpenGLGraphicsManager::notifyContextCreate(const Graphics::PixelFormat &def
 	// Query information needed by textures.
 	Texture::queryTextureInformation();
 
-#if !USE_FORCED_GL && !USE_FORCED_GLES && !USE_FORCED_GLES2
-	if (g_context.type == kContextGLES2) {
+#if !USE_FORCED_GLES
+	if (!_shader) {
+#if !USE_FORCED_GL && !USE_FORCED_GLES2
+		if (g_context.type == kContextGLES2) {
 #endif
-#if !USE_FORCED_GL && !USE_FORCED_GLES
-		if (!_shader) {
-			_shader = new Shader(g_defaultVertexShader, g_defaultFragmentShader);
+#if !USE_FORCED_GL
+			_shader = new ShaderGLES2(g_defaultVertexShader, g_defaultFragmentShaderGLES2);
+#endif
+#if !USE_FORCED_GL && !USE_FORCED_GLES2
+		} else {
+#endif
+#if !USE_FORCED_GLES2
+			if (g_context.shadersSupported) {
+				_shader = new ShaderARB(g_defaultVertexShader, g_defaultFragmentShaderGL);
+			}
+#endif
+#if !USE_FORCED_GL && !USE_FORCED_GLES2
 		}
+#endif
+	}
+#endif
 
+#if !USE_FORCED_GLES
+	if (_shader) {
 		// TODO: What do we do on failure?
 		_shader->recreate();
 		_shader->activate(_projectionMatrix);
-#endif
-#if !USE_FORCED_GL && !USE_FORCED_GLES && !USE_FORCED_GLES2
 	}
 #endif
 
@@ -999,7 +1023,7 @@ void OpenGLGraphicsManager::notifyContextDestroy() {
 	}
 #endif
 
-#if !USE_FORCED_GL && !USE_FORCED_GLES
+#if !USE_FORCED_GLES
 	if (_shader) {
 		_shader->destroy();
 	}
@@ -1080,16 +1104,24 @@ Texture *OpenGLGraphicsManager::createTexture(const Graphics::PixelFormat &forma
 
 void OpenGLGraphicsManager::setColor(GLfloat r, GLfloat g, GLfloat b, GLfloat a) {
 #if !USE_FORCED_GL && !USE_FORCED_GLES && !USE_FORCED_GLES2
-	if (g_context.type != kContextGLES2) {
+	if (g_context.type == kContextGLES2) {
 #endif
-#if !USE_FORCED_GLES2
-		GL_CALL(glColor4f(r, g, b, a));
+#if !USE_FORCED_GL && !USE_FORCED_GLES
+		GL_CALL(glVertexAttrib4f(kColorAttribLocation, r, g, b, a));
 #endif
 #if !USE_FORCED_GL && !USE_FORCED_GLES && !USE_FORCED_GLES2
 	} else {
 #endif
-#if !USE_FORCED_GL && !USE_FORCED_GLES
-		GL_CALL(glVertexAttrib4f(kColorAttribLocation, r, g, b, a));
+#if !USE_FORCED_GLES2
+#if !USE_FORCED_GLES
+		if (g_context.shadersSupported) {
+			GL_CALL(glVertexAttrib4fARB(kColorAttribLocation, r, g, b, a));
+		} else {
+#endif
+			GL_CALL(glColor4f(r, g, b, a));
+#if !USE_FORCED_GLES
+		}
+#endif
 #endif
 #if !USE_FORCED_GL && !USE_FORCED_GLES && !USE_FORCED_GLES2
 	}
diff --git a/backends/graphics/opengl/opengl-graphics.h b/backends/graphics/opengl/opengl-graphics.h
index 37ab1f8591..55e18cf7f0 100644
--- a/backends/graphics/opengl/opengl-graphics.h
+++ b/backends/graphics/opengl/opengl-graphics.h
@@ -41,7 +41,7 @@ namespace OpenGL {
 #define USE_OSD 1
 
 class Texture;
-#if !USE_FORCED_GL && !USE_FORCED_GLES
+#if !USE_FORCED_GLES
 class Shader;
 #endif
 
@@ -529,7 +529,7 @@ private:
 	 */
 	uint _scissorOverride;
 
-#if !USE_FORCED_GL && !USE_FORCED_GLES
+#if !USE_FORCED_GLES
 	//
 	// Shaders
 	//
diff --git a/backends/graphics/opengl/opengl-sys.h b/backends/graphics/opengl/opengl-sys.h
index ad36226a57..f8acb9302c 100644
--- a/backends/graphics/opengl/opengl-sys.h
+++ b/backends/graphics/opengl/opengl-sys.h
@@ -92,6 +92,11 @@ struct Context {
 	/** Whether GL_ARB_texture_non_power_of_two is available or not. */
 	bool NPOTSupported;
 
+#if !USE_FORCED_GLES && !USE_FORCED_GLES2
+	/** Whether shader support is available or not. */
+	bool shadersSupported;
+#endif
+
 #define GL_FUNC_DEF(ret, name, param) ret (GL_CALL_CONV *name)param
 #define GL_EXT_FUNC_DEF GL_FUNC_DEF
 #include "backends/graphics/opengl/opengl-func.h"
diff --git a/backends/graphics/opengl/shader.cpp b/backends/graphics/opengl/shader.cpp
index 6e36307860..c28036cb4e 100644
--- a/backends/graphics/opengl/shader.cpp
+++ b/backends/graphics/opengl/shader.cpp
@@ -22,7 +22,7 @@
 
 #include "backends/graphics/opengl/shader.h"
 
-#if !USE_FORCED_GL && !USE_FORCED_GLES
+#if !USE_FORCED_GLES
 
 #include "common/textconsole.h"
 
@@ -44,7 +44,20 @@ const char *const g_defaultVertexShader =
 	"\tgl_Position = projection * position;\n"
 	"}\n";
 
-const char *const g_defaultFragmentShader =
+#if !USE_FORCED_GLES2
+const char *const g_defaultFragmentShaderGL =
+	"varying vec2 texCoord;\n"
+	"varying vec4 blendColor;\n"
+	"\n"
+	"uniform sampler2D texture;\n"
+	"\n"
+	"void main(void) {\n"
+	"\tgl_FragColor = blendColor * texture2D(texture, texCoord);\n"
+	"}\n";
+#endif
+
+#if !USE_FORCED_GL
+const char *const g_defaultFragmentShaderGLES2 =
 	"varying lowp vec2 texCoord;\n"
 	"varying lowp vec4 blendColor;\n"
 	"\n"
@@ -53,17 +66,146 @@ const char *const g_defaultFragmentShader =
 	"void main(void) {\n"
 	"\tgl_FragColor = blendColor * texture2D(texture, texCoord);\n"
 	"}\n";
+#endif
+
+#if !USE_FORCED_GLES2
+
+ShaderARB::ShaderARB(const Common::String &vertex, const Common::String &fragment)
+    : Shader(vertex, fragment), _program(0), _projectionLocation(-1), _textureLocation(-1) {
+}
 
-Shader::Shader(const Common::String &vertex, const Common::String &fragment)
-    : _vertex(vertex), _fragment(fragment), _program(0), _projectionLocation(-1), _textureLocation(-1) {
+void ShaderARB::destroy() {
+	// According to extension specification glDeleteObjectARB silently ignores
+	// 0. However, with nVidia drivers this can cause GL_INVALID_VALUE, thus
+	// we do not call it with 0 as parameter to avoid warnings.
+	if (_program) {
+		GL_CALL(glDeleteObjectARB(_program));
+	}
+	_program = 0;
 }
 
-void Shader::destroy() {
+bool ShaderARB::recreate() {
+	// Make sure any old programs are destroyed properly.
+	destroy();
+
+	GLhandleARB vertexShader = compileShader(_vertex.c_str(), GL_VERTEX_SHADER_ARB);
+	if (!vertexShader) {
+		return false;
+	}
+
+	GLhandleARB fragmentShader = compileShader(_fragment.c_str(), GL_FRAGMENT_SHADER_ARB);
+	if (!fragmentShader) {
+		GL_CALL(glDeleteObjectARB(vertexShader));
+		return false;
+	}
+
+	GL_ASSIGN(_program, glCreateProgramObjectARB());
+	if (!_program) {
+		GL_CALL(glDeleteObjectARB(vertexShader));
+		GL_CALL(glDeleteObjectARB(fragmentShader));
+		return false;
+	}
+
+	GL_CALL(glAttachObjectARB(_program, vertexShader));
+	GL_CALL(glAttachObjectARB(_program, fragmentShader));
+
+	GL_CALL(glBindAttribLocationARB(_program, kPositionAttribLocation, "position"));
+	GL_CALL(glBindAttribLocationARB(_program, kTexCoordAttribLocation, "texCoordIn"));
+	GL_CALL(glBindAttribLocationARB(_program, kColorAttribLocation,    "blendColorIn"));
+
+	GL_CALL(glLinkProgramARB(_program));
+
+	GL_CALL(glDetachObjectARB(_program, fragmentShader));
+	GL_CALL(glDeleteObjectARB(fragmentShader));
+
+	GL_CALL(glDetachObjectARB(_program, vertexShader));
+	GL_CALL(glDeleteObjectARB(vertexShader));
+
+	GLint result;
+	GL_CALL(glGetObjectParameterivARB(_program, GL_OBJECT_LINK_STATUS_ARB, &result));
+	if (result == GL_FALSE) {
+		GLint logSize;
+		GL_CALL(glGetObjectParameterivARB(_program, GL_OBJECT_INFO_LOG_LENGTH_ARB, &logSize));
+
+		GLchar *log = new GLchar[logSize];
+		GL_CALL(glGetInfoLogARB(_program, logSize, nullptr, log));
+		warning("Could not link shader: \"%s\"", log);
+		delete[] log;
+
+		destroy();
+		return false;
+	}
+
+	GL_ASSIGN(_projectionLocation, glGetUniformLocationARB(_program, "projection"));
+	if (_projectionLocation == -1) {
+		warning("Shader misses \"projection\" uniform.");
+		destroy();
+		return false;
+	}
+
+	GL_ASSIGN(_textureLocation, glGetUniformLocationARB(_program, "texture"));
+	if (_textureLocation == -1) {
+		warning("Shader misses \"texture\" uniform.");
+		destroy();
+		return false;
+	}
+
+	return true;
+}
+
+void ShaderARB::activate(const GLfloat *projectionMatrix) {
+	// Activate program.
+	GL_CALL(glUseProgramObjectARB(_program));
+
+	// Set projection matrix.
+	GL_CALL(glUniformMatrix4fvARB(_projectionLocation, 1, GL_FALSE, projectionMatrix));
+
+	// We always use texture unit 0.
+	GL_CALL(glUniform1iARB(_textureLocation, 0));
+}
+
+GLhandleARB ShaderARB::compileShader(const char *source, GLenum shaderType) {
+	GLuint handle;
+	GL_ASSIGN(handle, glCreateShaderObjectARB(shaderType));
+	if (!handle) {
+		return 0;
+	}
+
+	GL_CALL(glShaderSourceARB(handle, 1, &source, nullptr));
+	GL_CALL(glCompileShaderARB(handle));
+
+	GLint result;
+	GL_CALL(glGetObjectParameterivARB(handle, GL_OBJECT_COMPILE_STATUS_ARB, &result));
+	if (result == GL_FALSE) {
+		GLint logSize;
+		GL_CALL(glGetObjectParameterivARB(handle, GL_OBJECT_INFO_LOG_LENGTH_ARB, &logSize));
+
+		GLchar *log = new GLchar[logSize];
+		GL_CALL(glGetInfoLogARB(handle, logSize, nullptr, log));
+		warning("Could not compile shader \"%s\": \"%s\"", source, log);
+		delete[] log;
+
+		GL_CALL(glDeleteObjectARB(handle));
+		return 0;
+	}
+
+	return handle;
+}
+
+#endif // !USE_FORCED_GLES2
+
+#if !USE_FORCED_GL
+
+ShaderGLES2::ShaderGLES2(const Common::String &vertex, const Common::String &fragment)
+    : Shader(vertex, fragment), _program(0), _projectionLocation(-1), _textureLocation(-1) {
+}
+
+void ShaderGLES2::destroy() {
 	GL_CALL(glDeleteProgram(_program));
 	_program = 0;
 }
 
-bool Shader::recreate() {
+bool ShaderGLES2::recreate() {
 	// Make sure any old programs are destroyed properly.
 	destroy();
 
@@ -132,7 +274,7 @@ bool Shader::recreate() {
 	return true;
 }
 
-void Shader::activate(const GLfloat *projectionMatrix) {
+void ShaderGLES2::activate(const GLfloat *projectionMatrix) {
 	// Activate program.
 	GL_CALL(glUseProgram(_program));
 
@@ -143,7 +285,7 @@ void Shader::activate(const GLfloat *projectionMatrix) {
 	GL_CALL(glUniform1i(_textureLocation, 0));
 }
 
-GLuint Shader::compileShader(const char *source, GLenum shaderType) {
+GLuint ShaderGLES2::compileShader(const char *source, GLenum shaderType) {
 	GLuint handle;
 	GL_ASSIGN(handle, glCreateShader(shaderType));
 	if (!handle) {
@@ -171,6 +313,8 @@ GLuint Shader::compileShader(const char *source, GLenum shaderType) {
 	return handle;
 }
 
+#endif // !!USE_FORCED_GL
+
 } // End of namespace OpenGL
 
-#endif // !USE_FORCED_GL && !USE_FORCED_GLES
+#endif // !USE_FORCED_GLES
diff --git a/backends/graphics/opengl/shader.h b/backends/graphics/opengl/shader.h
index e8535e0225..8c457f8f91 100644
--- a/backends/graphics/opengl/shader.h
+++ b/backends/graphics/opengl/shader.h
@@ -25,7 +25,7 @@
 
 #include "backends/graphics/opengl/opengl-sys.h"
 
-#if !USE_FORCED_GL && !USE_FORCED_GLES
+#if !USE_FORCED_GLES
 
 #include "common/str.h"
 
@@ -38,12 +38,18 @@ enum {
 };
 
 extern const char *const g_defaultVertexShader;
-extern const char *const g_defaultFragmentShader;
+#if !USE_FORCED_GLES2
+extern const char *const g_defaultFragmentShaderGL;
+#endif
+#if !USE_FORCED_GL
+extern const char *const g_defaultFragmentShaderGLES2;
+#endif
 
 class Shader {
 public:
-	Shader(const Common::String &vertex, const Common::String &fragment);
-	~Shader() { destroy(); }
+	Shader(const Common::String &vertex, const Common::String &fragment)
+	    : _vertex(vertex), _fragment(fragment) {}
+	virtual ~Shader() {}
 
 	/**
 	 * Destroy the shader program.
@@ -51,22 +57,22 @@ public:
 	 * This keeps the vertex and fragment shader sources around and thus
 	 * allows for recreating the shader on context recreation.
 	 */
-	void destroy();
+	virtual void destroy() = 0;
 
 	/**
 	 * Recreate shader program.
 	 *
 	 * @return true on success, false on failure.
 	 */
-	bool recreate();
+	virtual bool recreate() = 0;
 
 	/**
 	 * Make shader active.
 	 *
 	 * @param projectionMatrix Projection matrix to use.
 	 */
-	void activate(const GLfloat *projectionMatrix);
-private:
+	virtual void activate(const GLfloat *projectionMatrix) = 0;
+protected:
 	/**
 	 * Vertex shader sources.
 	 */
@@ -76,7 +82,59 @@ private:
 	 * Fragment shader sources.
 	 */
 	const Common::String _fragment;
+};
+
+#if !USE_FORCED_GLES2
+class ShaderARB : public Shader {
+public:
+	ShaderARB(const Common::String &vertex, const Common::String &fragment);
+	virtual ~ShaderARB() { destroy(); }
+
+	virtual void destroy();
+
+	virtual bool recreate();
 
+	virtual void activate(const GLfloat *projectionMatrix);
+private:
+	/**
+	 * Shader program handle.
+	 */
+	GLhandleARB _program;
+
+	/**
+	 * Location of the matrix uniform in the shader program.
+	 */
+	GLint _projectionLocation;
+
+	/**
+	 * Location of the texture sampler location in the shader program.
+	 */
+	GLint _textureLocation;
+
+	/**
+	 * Compile a vertex or fragment shader.
+	 *
+	 * @param source     Sources to the shader.
+	 * @param shaderType Type of shader to compile (GL_FRAGMENT_SHADER_ARB or
+	 *                   GL_VERTEX_SHADER_ARB)
+	 * @return The shader object or 0 on failure.
+	 */
+	static GLhandleARB compileShader(const char *source, GLenum shaderType);
+};
+#endif // !USE_FORCED_GLES2
+
+#if !USE_FORCED_GL
+class ShaderGLES2 : public Shader {
+public:
+	ShaderGLES2(const Common::String &vertex, const Common::String &fragment);
+	virtual ~ShaderGLES2() { destroy(); }
+
+	virtual void destroy();
+
+	virtual bool recreate();
+
+	virtual void activate(const GLfloat *projectionMatrix);
+private:
 	/**
 	 * Shader program handle.
 	 */
@@ -102,9 +160,10 @@ private:
 	 */
 	static GLuint compileShader(const char *source, GLenum shaderType);
 };
+#endif
 
 } // End of namespace OpenGL
 
-#endif // !USE_FORCED_GL && !USE_FORCED_GLES
+#endif // !USE_FORCED_GLES
 
 #endif
diff --git a/backends/graphics/opengl/texture.cpp b/backends/graphics/opengl/texture.cpp
index c8c38edbbd..0b01430728 100644
--- a/backends/graphics/opengl/texture.cpp
+++ b/backends/graphics/opengl/texture.cpp
@@ -196,18 +196,27 @@ void Texture::draw(GLfloat x, GLfloat y, GLfloat w, GLfloat h) {
 	};
 
 #if !USE_FORCED_GL && !USE_FORCED_GLES && !USE_FORCED_GLES2
-	if (g_context.type != kContextGLES2) {
+	if (g_context.type == kContextGLES2) {
 #endif
-#if !USE_FORCED_GLES2
-		GL_CALL(glTexCoordPointer(2, GL_FLOAT, 0, texcoords));
-		GL_CALL(glVertexPointer(2, GL_FLOAT, 0, vertices));
+#if !USE_FORCED_GL && !USE_FORCED_GLES
+		GL_CALL(glVertexAttribPointer(kTexCoordAttribLocation, 2, GL_FLOAT, GL_FALSE, 0, texcoords));
+		GL_CALL(glVertexAttribPointer(kPositionAttribLocation, 2, GL_FLOAT, GL_FALSE, 0, vertices));
 #endif
 #if !USE_FORCED_GL && !USE_FORCED_GLES && !USE_FORCED_GLES2
 	} else {
 #endif
-#if !USE_FORCED_GL && !USE_FORCED_GLES
-		GL_CALL(glVertexAttribPointer(kTexCoordAttribLocation, 2, GL_FLOAT, GL_FALSE, 0, texcoords));
-		GL_CALL(glVertexAttribPointer(kPositionAttribLocation, 2, GL_FLOAT, GL_FALSE, 0, vertices));
+#if !USE_FORCED_GLES2
+#if !USE_FORCED_GLES
+		if (g_context.shadersSupported) {
+			GL_CALL(glVertexAttribPointerARB(kTexCoordAttribLocation, 2, GL_FLOAT, GL_FALSE, 0, texcoords));
+			GL_CALL(glVertexAttribPointerARB(kPositionAttribLocation, 2, GL_FLOAT, GL_FALSE, 0, vertices));
+		} else {
+#endif
+			GL_CALL(glTexCoordPointer(2, GL_FLOAT, 0, texcoords));
+			GL_CALL(glVertexPointer(2, GL_FLOAT, 0, vertices));
+#if !USE_FORCED_GLES
+		}
+#endif
 #endif
 #if !USE_FORCED_GL && !USE_FORCED_GLES && !USE_FORCED_GLES2
 	}