OPENGL: Allow engines to detect OpenGL info without switching

For now only OpenGL type and shaders support are available

backends/platform/android/android.cpp

@@ -509,6 +509,8 @@ bool OSystem_Android::hasFeature(Feature f) {
 	/* Even if we are using the 2D graphics manager,
 	 * we are at one initGraphics3d call of supporting GLES2 */
 	if (f == kFeatureOpenGLForGame) return true;
+	/* GLES2 always supports shaders */
+	if (f == kFeatureShadersForGame) return true;
 	return ModularGraphicsBackend::hasFeature(f);
 }
 

backends/platform/android/android.h

@@ -192,6 +192,8 @@ public:
 	bool setGraphicsMode(int mode, uint flags) override;
 	int getGraphicsMode() const override;
 
+	OpenGL::ContextOGLType getOpenGLType() const override { return OpenGL::kOGLContextGLES2; }
+
 #ifdef ANDROID_DEBUG_GL_CALLS
 	bool isRunningInMainThread() { return pthread_self() == _main_thread; }
 #endif

backends/platform/sdl/sdl.cpp

@@ -184,6 +184,7 @@ bool OSystem_SDL::hasFeature(Feature f) {
 	/* Even if we are using the 2D graphics manager,
 	 * we are at one initGraphics3d call of supporting OpenGL */
 	if (f == kFeatureOpenGLForGame) return true;
+	if (f == kFeatureShadersForGame) return _supportsShaders;
 #endif
 	return ModularGraphicsBackend::hasFeature(f);
 }
@@ -221,7 +222,7 @@ void OSystem_SDL::initBackend() {
 	debug(1, "Using SDL Video Driver \"%s\"", sdlDriverName);
 
 #if defined(USE_OPENGL_GAME) || defined(USE_OPENGL_SHADERS)
-	detectFramebufferSupport();
+	detectOpenGLFeaturesSupport();
 	detectAntiAliasingSupport();
 #endif
 
@@ -318,11 +319,15 @@ void OSystem_SDL::initBackend() {
 }
 
 #if defined(USE_OPENGL_GAME) || defined(USE_OPENGL_SHADERS)
-void OSystem_SDL::detectFramebufferSupport() {
+void OSystem_SDL::detectOpenGLFeaturesSupport() {
+	_oglType = OpenGL::kOGLContextNone;
 	_supportsFrameBuffer = false;
+	_supportsShaders = false;
 #if USE_FORCED_GLES2
-	// Framebuffers are always available with GLES2
+	// Framebuffers and shaders are always available with GLES2
+	_oglType = kOGLContextGLES2;
 	_supportsFrameBuffer = true;
+	_supportsShaders = true;
 #elif !defined(AMIGAOS) && !defined(__MORPHOS__)
 	// Spawn a 32x32 window off-screen with a GL context to test if framebuffers are supported
 #if SDL_VERSION_ATLEAST(2, 0, 0)
@@ -332,7 +337,6 @@ void OSystem_SDL::detectFramebufferSupport() {
 	}
 
 	int glContextProfileMask, glContextMajor;
-	OpenGL::ContextOGLType glContextType;
 	if (SDL_GL_GetAttribute(SDL_GL_CONTEXT_PROFILE_MASK, &glContextProfileMask) != 0) {
 		SDL_DestroyWindow(window);
 		return;
@@ -343,13 +347,13 @@ void OSystem_SDL::detectFramebufferSupport() {
 			return;
 		}
 		if (glContextMajor == 2) {
-			glContextType = OpenGL::kOGLContextGLES2;
+			_oglType = OpenGL::kOGLContextGLES2;
 		} else {
 			SDL_DestroyWindow(window);
 			return;
 		}
 	} else {
-		glContextType = OpenGL::kOGLContextGL;
+		_oglType = OpenGL::kOGLContextGL;
 	}
 	SDL_GLContext glContext = SDL_GL_CreateContext(window);
 	if (!glContext) {
@@ -357,8 +361,9 @@ void OSystem_SDL::detectFramebufferSupport() {
 		return;
 	}
 
-	OpenGLContext.initialize(glContextType);
+	OpenGLContext.initialize(_oglType);
 	_supportsFrameBuffer = OpenGLContext.framebufferObjectSupported;
+	_supportsShaders = OpenGLContext.shadersSupported;
 	OpenGLContext.reset();
 	SDL_GL_DeleteContext(glContext);
 	SDL_DestroyWindow(window);
@@ -367,8 +372,10 @@ void OSystem_SDL::detectFramebufferSupport() {
 	SDL_SetVideoMode(32, 32, 0, SDL_OPENGL);
 	SDL_putenv(const_cast<char *>("SDL_VIDEO_WINDOW_POS=center"));
 	// SDL 1.2 only supports OpenGL
-	OpenGLContext.initialize(OpenGL::kOGLContextGL);
+	_oglType = OpenGL::kOGLContextGL;
+	OpenGLContext.initialize(_oglType);
 	_supportsFrameBuffer = OpenGLContext.framebufferObjectSupported;
+	_supportsShaders = OpenGLContext.shadersSupported;
 	OpenGLContext.reset();
 #endif
 #endif

backends/platform/sdl/sdl.h

@@ -95,6 +95,7 @@ public:
 
 #if defined(USE_OPENGL_GAME) || defined(USE_OPENGL_SHADERS)
 	Common::Array<uint> getSupportedAntiAliasingLevels() const override;
+	OpenGL::ContextOGLType getOpenGLType() const override { return _oglType; }
 #endif
 
 protected:
@@ -139,10 +140,12 @@ protected:
 
 #if defined(USE_OPENGL_GAME) || defined(USE_OPENGL_SHADERS)
 	// Graphics capabilities
-	void detectFramebufferSupport();
+	void detectOpenGLFeaturesSupport();
 	void detectAntiAliasingSupport();
 
+	OpenGL::ContextOGLType _oglType;
 	bool _supportsFrameBuffer;
+	bool _supportsShaders;
 	Common::Array<uint> _antiAliasLevels;
 #endif
 

common/system.h

@@ -29,6 +29,7 @@
 #include "common/ustr.h"
 #include "graphics/pixelformat.h"
 #include "graphics/mode.h"
+#include "graphics/opengl/context.h"
 
 namespace Audio {
 class Mixer;
@@ -406,6 +407,12 @@ public:
 		 */
 		kFeatureOpenGLForGame,
 
+		/**
+		 * This feature flag can be used to check if shaders are supported
+		 * and can be used for 3D game rendering.
+		 */
+		kFeatureShadersForGame,
+
 		/**
 		 * If supported, this feature flag can be used to check if
 		 * waiting for vertical sync before refreshing the screen to reduce
@@ -728,6 +735,20 @@ public:
 		return Common::Array<uint>();
 	}
 
+	/**
+	 * Return the chosen OpenGL type.
+	 *
+	 * This function works even when a 2D graphical manager is active and
+	 * let to select a proper renderer before changing mode.
+	 * Implementation having feature kFeatureOpenGLForGame are expected to
+	 * override this function.
+	 *
+	 * @return the OpenGL type of context which is supported.
+	 */
+	virtual OpenGL::ContextOGLType getOpenGLType() const {
+		return OpenGL::kOGLContextNone;
+	}
+
 	/**
 	 * Retrieve a list of all hardware shaders supported by this backend.
 	 *

graphics/opengl/context.cpp

@@ -71,6 +71,7 @@ ContextGL::ContextGL() {
 }
 
 void ContextGL::reset() {
+	type = kOGLContextNone;
 	maxTextureSize = 0;
 
 	NPOTSupported = false;
@@ -86,6 +87,9 @@ void ContextGL::reset() {
 void ContextGL::initialize(ContextOGLType contextType) {
 	// Initialize default state.
 	reset();
+	if (contextType == kOGLContextNone) {
+		return;
+	}
 
 	type = contextType;
 
@@ -178,6 +182,9 @@ void ContextGL::initialize(ContextOGLType contextType) {
 
 	// Log context type.
 	switch (type) {
+		case kOGLContextNone:
+			/* Shouldn't happen */
+			break;
 		case kOGLContextGL:
 			debug(5, "OpenGL: GL context initialized");
 			break;

graphics/opengl/context.h

@@ -27,6 +27,7 @@
 namespace OpenGL {
 
 enum ContextOGLType {
+	kOGLContextNone,
 	kOGLContextGL,
 	kOGLContextGLES2
 };