runtime caps for opengl

src/base.err

@@ -19,4 +19,6 @@ ECODE(ERR_ENGINESTART,
 ECODE(ERR_INVRASTER,
       "Invalid raster format"),
 ECODE(ERR_NOTEXTURE,
-      "Could not create texture")
+      "Could not create texture"),
+ECODE(ERR_FORMAT_UNSUPPORTED,
+      "Unsupported raster format")

src/gl/gl3device.cpp

@@ -59,6 +59,8 @@ struct GlGlobals
 	const char *winTitle;
 } glGlobals;
 
+Gl3Caps gl3Caps;
+
 int32   alphaFunc;
 float32 alphaRef;
 
@@ -1498,6 +1500,18 @@ stopGLFW(void)
 static int
 initOpenGL(void)
 {
+	memset(&gl3Caps, 0, sizeof(gl3Caps));
+	int numExt;
+	glGetIntegerv(GL_NUM_EXTENSIONS, &numExt);
+	for(int i = 0; i < numExt; i++){
+		const char *ext = (const char*)glGetStringi(GL_EXTENSIONS, i);
+		if(strcmp(ext, "GL_EXT_texture_compression_s3tc") == 0)
+			gl3Caps.dxtSupported = true;
+		else if(strcmp(ext, "GL_KHR_texture_compression_astc_ldr") == 0)
+			gl3Caps.astcSupported = true;
+//		printf("%d %s\n", i, ext);
+	}
+
 #ifndef RW_GL_USE_UBOS
 	u_alphaRef = registerUniform("u_alphaRef");
 	u_fogData = registerUniform("u_fogData");

src/gl/gl3raster.cpp

@@ -769,6 +769,11 @@ readNativeTexture(Stream *stream)
 	Raster *raster;
 	Gl3Raster *natras;
 	if(flags & 2){
+		if(!gl3Caps.dxtSupported){
+			tex->destroy();
+			RWERROR((ERR_FORMAT_UNSUPPORTED));
+			return nil;
+		}
 		raster = Raster::create(width, height, depth, format | Raster::TEXTURE | Raster::DONTALLOCATE, PLATFORM_GL3);
 		allocateDXT(raster, compression, numLevels, flags & 1);
 	}else{

src/gl/rwgl3.h

@@ -246,6 +246,14 @@ struct Gl3Raster
 	Raster *fboMate;	// color or zbuffer raster mate of this one
 };
 
+struct Gl3Caps
+{
+	// TODO: put more stuff into this
+	bool dxtSupported;
+	bool astcSupported;	// not used yet
+};
+extern Gl3Caps gl3Caps;
+
 void allocateDXT(Raster *raster, int32 dxt, int32 numLevels, bool32 hasAlpha);
 
 Texture *readNativeTexture(Stream *stream);

src/raster.cpp

@@ -419,6 +419,9 @@ d3d_to_gl3(rw::Raster *ras)
 #ifdef RW_GL3
 	using namespace rw;
 
+	if(!gl3::gl3Caps.dxtSupported)
+		return nil;
+
 	int dxt = 0;
 	d3d::D3dRaster *d3dras = GETD3DRASTEREXT(ras);
 	if(d3dras->customFormat){