GS/GL: Check if function pointers are actually supported for extensions.

On older mesa versions GLAD_GL_ARB_draw_buffers_blend flag is set enabled as supported, however glBlendFuncSeparatei is null which results in a crash so what we can do is also check if the pointers are working.

Also check for GLAD_GL_ARB_viewport_array , GLAD_GL_ARB_texture_barrier , GLAD_GL_ARB_direct_state_access.

We want to make sure they are supported, otherwise it will result in a crash.

Author: lightningterror

pcsx2/GS/Renderers/OpenGL/GSDeviceOGL.cpp

@@ -43,8 +43,29 @@ namespace ReplaceGL
 		glViewport(GLint(x), GLint(y), GLsizei(w), GLsizei(h));
 	}
 
+	static void GLAPIENTRY BlendEquationSeparatei(GLuint index, GLenum op, GLenum op_alpha)
+	{
+		glBlendEquationSeparate(op, op_alpha);
+	}
+
+	static void GLAPIENTRY BlendFuncSeparatei(GLuint index, GLenum src_factor, GLenum dst_factor, GLenum src_factor_alpha, GLenum dst_factor_alpha)
+	{
+		glBlendFuncSeparate(src_factor, dst_factor, src_factor_alpha, dst_factor_alpha);
+	}
+
+	static void GLAPIENTRY Enablei(GLenum target, GLuint index)
+	{
+		glEnable(target);
+	}
+
+	static void GLAPIENTRY Disablei(GLenum target, GLuint index)
+	{
+		glDisable(target);
+	}
+
 	static void GLAPIENTRY TextureBarrier()
 	{
+
 	}
 
 } // namespace ReplaceGL
@@ -742,21 +763,49 @@ bool GSDeviceOGL::CheckFeatures()
 		return false;
 	}
 
-	if (!GLAD_GL_ARB_viewport_array)
+	// GLAD_GL_ARB_viewport_array
+	const bool viewport_array_function_pointers = glScissorIndexed &&
+	                                              glViewportIndexedf;
+	if (!GLAD_GL_ARB_viewport_array || !viewport_array_function_pointers)
 	{
 		glScissorIndexed = ReplaceGL::ScissorIndexed;
 		glViewportIndexedf = ReplaceGL::ViewportIndexedf;
 		Console.Warning("GL_ARB_viewport_array is not supported! Function pointer will be replaced.");
 	}
 
-	if (!GLAD_GL_ARB_texture_barrier)
+	// GLAD_GL_ARB_draw_buffers_blend
+	const bool draw_buffers_blend_function_pointers = glEnablei &&
+	                                                  glDisablei &&
+	                                                  glBlendEquationSeparatei &&
+	                                                  glBlendFuncSeparatei;
+	if (!GLAD_GL_ARB_draw_buffers_blend || !draw_buffers_blend_function_pointers)
+	{
+		glEnablei = ReplaceGL::Enablei;
+		glDisablei = ReplaceGL::Disablei;
+		glBlendEquationSeparatei = ReplaceGL::BlendEquationSeparatei;
+		glBlendFuncSeparatei = ReplaceGL::BlendFuncSeparatei;
+		Console.Warning("GL_ARB_draw_buffers_blend is not supported! Function pointer will be replaced.");
+	}
+
+	// GLAD_GL_ARB_texture_barrier
+	if (!GLAD_GL_ARB_texture_barrier || !glTextureBarrier)
 	{
 		glTextureBarrier = ReplaceGL::TextureBarrier;
 		Host::AddOSDMessage(
 			"GL_ARB_texture_barrier is not supported, blending will not be accurate.", Host::OSD_ERROR_DURATION);
 	}
 
-	if (!GLAD_GL_ARB_direct_state_access)
+	// GLAD_GL_ARB_direct_state_access
+	const bool direct_state_access_init_function_pointers = glBindTextureUnit &&
+	                                                        glCreateTextures &&
+	                                                        glTextureStorage2D &&
+	                                                        glTextureSubImage2D &&
+	                                                        glCompressedTextureSubImage2D &&
+	                                                        glGetTextureImage &&
+	                                                        glTextureParameteri &&
+	                                                        glGenerateTextureMipmap &&
+	                                                        glCreateSamplers;
+	if (!GLAD_GL_ARB_direct_state_access || !direct_state_access_init_function_pointers)
 	{
 		Console.Warning("GL_ARB_direct_state_access is not supported, this will reduce performance.");
 		Emulate_DSA::Init();