Implement EXT_discard_framebuffer for the GL backend.

src/libANGLE/renderer/gl/FramebufferGL.cpp

@@ -127,20 +127,25 @@ static void BindFramebufferAttachment(const FunctionsGL *functions,
 
 Error FramebufferGL::discard(size_t count, const GLenum *attachments)
 {
-    UNIMPLEMENTED();
-    return Error(GL_INVALID_OPERATION);
+    // glInvalidateFramebuffer accepts the same enums as glDiscardFramebufferEXT
+    return invalidate(count, attachments);
 }
 
 Error FramebufferGL::invalidate(size_t count, const GLenum *attachments)
 {
-    // Since this function is just a hint and not available until OpenGL 4.3, only call it if it is available.
+    // Since this function is just a hint, only call a native function if it exists.
     if (mFunctions->invalidateFramebuffer)
     {
         mStateManager->bindFramebuffer(GL_FRAMEBUFFER, mFramebufferID);
         mFunctions->invalidateFramebuffer(GL_FRAMEBUFFER, static_cast<GLsizei>(count), attachments);
     }
+    else if (mFunctions->discardFramebuffer)
+    {
+        mStateManager->bindFramebuffer(GL_FRAMEBUFFER, mFramebufferID);
+        mFunctions->discardFramebuffer(GL_FRAMEBUFFER, static_cast<GLsizei>(count), attachments);
+    }
 
-    return Error(GL_NO_ERROR);
+    return gl::NoError();
 }
 
 Error FramebufferGL::invalidateSub(size_t count,

src/libANGLE/renderer/gl/FunctionsGL.cpp

@@ -788,7 +788,8 @@ FunctionsGL::FunctionsGL()
       blendBarrier(nullptr),
       primitiveBoundingBox(nullptr),
       eglImageTargetRenderbufferStorageOES(nullptr),
-      eglImageTargetTexture2DOES(nullptr)
+      eglImageTargetTexture2DOES(nullptr),
+      discardFramebuffer(nullptr)
 {
 }
 
@@ -1029,6 +1030,14 @@ void FunctionsGL::initializeProcsDesktopGL()
     // GL_KHR_robustness
     AssignGLExtensionEntryPoint(extensions, "GL_KHR_robustness", loadProcAddress("glGetGraphicsResetStatus"), &getGraphicsResetStatus);
 
+    // GL_ARB_invalidate_subdata
+    AssignGLExtensionEntryPoint(extensions, "GL_ARB_invalidate_subdata", loadProcAddress("glInvalidateTexSubImage"), &invalidateTexSubImage);
+    AssignGLExtensionEntryPoint(extensions, "GL_ARB_invalidate_subdata", loadProcAddress("glInvalidateTexImage"), &invalidateTexImage);
+    AssignGLExtensionEntryPoint(extensions, "GL_ARB_invalidate_subdata", loadProcAddress("glInvalidateBufferSubData"), &invalidateBufferSubData);
+    AssignGLExtensionEntryPoint(extensions, "GL_ARB_invalidate_subdata", loadProcAddress("glInvalidateBufferData"), &invalidateBufferData);
+    AssignGLExtensionEntryPoint(extensions, "GL_ARB_invalidate_subdata", loadProcAddress("glInvalidateFramebuffer"), &invalidateFramebuffer);
+    AssignGLExtensionEntryPoint(extensions, "GL_ARB_invalidate_subdata", loadProcAddress("glInvalidateSubFramebuffer"), &invalidateSubFramebuffer);
+
     // 1.0
     if (isAtLeastGL(gl::Version(1, 0)))
     {
@@ -1897,6 +1906,9 @@ void FunctionsGL::initializeProcsGLES()
     // GL_KHR_robustness
     AssignGLExtensionEntryPoint(extensions, "GL_KHR_robustness", loadProcAddress("glGetGraphicsResetStatusKHR"), &getGraphicsResetStatus);
 
+    // GL_EXT_discard_framebuffer
+    AssignGLExtensionEntryPoint(extensions, "GL_EXT_discard_framebuffer", loadProcAddress("glDiscardFramebufferEXT"), &discardFramebuffer);
+
     // 2.0
     if (isAtLeastGLES(gl::Version(2, 0)))
     {

src/libANGLE/renderer/gl/FunctionsGL.h

@@ -775,10 +775,13 @@ class FunctionsGL
     PFNGLBLENDBARRIERPROC blendBarrier;
     PFNGLPRIMITIVEBOUNDINGBOXPROC primitiveBoundingBox;
 
-    // ES extensions
+    // GL_OES_EGL_image
     PFNGLEGLIMAGETARGETRENDERBUFFERSTORAGEOESPROC eglImageTargetRenderbufferStorageOES;
     PFNGLEGLIMAGETARGETTEXTURE2DOESPROC eglImageTargetTexture2DOES;
 
+    // GL_EXT_discard_framebuffer
+    PFNGLDISCARDFRAMEBUFFEREXTPROC discardFramebuffer;
+
   private:
     void initializeProcsDesktopGL();
     void initializeProcsGLES();

src/libANGLE/renderer/gl/renderergl_utils.cpp

@@ -899,6 +899,14 @@ void GenerateCaps(const FunctionsGL *functions, gl::Caps *caps, gl::TextureCapsM
     // Disabling GL_FRAMEBUFFER_SRGB will then convert in the wrong direction.
     extensions->sRGBWriteControl = false;
 #endif
+
+    // EXT_discard_framebuffer can be implemented as long as glDiscardFramebufferEXT or
+    // glInvalidateFramebuffer is available
+    extensions->discardFramebuffer = functions->isAtLeastGL(gl::Version(4, 3)) ||
+                                     functions->hasGLExtension("GL_ARB_invalidate_subdata") ||
+                                     functions->isAtLeastGLES(gl::Version(3, 0)) ||
+                                     functions->hasGLESExtension("GL_EXT_discard_framebuffer") ||
+                                     functions->hasGLESExtension("GL_ARB_invalidate_subdata");
 }
 
 void GenerateWorkarounds(const FunctionsGL *functions, WorkaroundsGL *workarounds)

src/tests/gl_tests/DiscardFramebufferEXTTest.cpp

@@ -24,21 +24,6 @@ protected:
     }
 };
 
-TEST_P(DiscardFramebufferEXTTest, ExtensionEnabled)
-{
-    EGLPlatformParameters platform = GetParam().eglParameters;
-
-    if (platform.renderer == EGL_PLATFORM_ANGLE_TYPE_D3D11_ANGLE)
-    {
-        EXPECT_TRUE(extensionEnabled("EXT_discard_framebuffer"));
-    }
-    else
-    {
-        // Other platforms don't currently implement this extension
-        EXPECT_FALSE(extensionEnabled("EXT_discard_framebuffer"));
-    }
-}
-
 TEST_P(DiscardFramebufferEXTTest, DefaultFramebuffer)
 {
     if (!extensionEnabled("EXT_discard_framebuffer"))