FramebufferGL: Fix blit workaround corner case

src/libANGLE/renderer/gl/FramebufferGL.cpp

@@ -283,12 +283,13 @@ Error FramebufferGL::blit(ContextImpl *context,
     const Framebuffer *sourceFramebuffer     = context->getGLState().getReadFramebuffer();
     const Framebuffer *destFramebuffer       = context->getGLState().getDrawFramebuffer();
 
+    const FramebufferAttachment *colorReadAttachment = sourceFramebuffer->getReadColorbuffer();
+    GLsizei readAttachmentSamples                    = colorReadAttachment->getSamples();
+
     bool needManualColorBlit = false;
 
-    // The manual SRGB blit is only needed to perform correct linear interpolation. We don't
-    // need to make sure there is SRGB conversion for NEAREST as the values will be copied.
-    if (filter != GL_NEAREST)
-    {
+    // TODO(cwallez) when the filter is LINEAR and both source and destination are SRGB, we
+    // could avoid doing a manual blit.
 
     // Prior to OpenGL 4.4 BlitFramebuffer (section 18.3.1 of GL 4.3 core profile) reads:
     //      When values are taken from the read buffer, no linearization is performed, even
@@ -299,9 +300,8 @@ Error FramebufferGL::blit(ContextImpl *context,
     //      corresponding to the read buffer is SRGB, the red, green, and blue components are
     //      converted from the non-linear sRGB color space according [...].
     {
-            const FramebufferAttachment *readAttachment = sourceFramebuffer->getReadColorbuffer();
-            bool sourceSRGB =
-                readAttachment != nullptr && readAttachment->getColorEncoding() == GL_SRGB;
+        bool sourceSRGB = colorReadAttachment != nullptr &&
+                          colorReadAttachment->getColorEncoding() == GL_SRGB;
         needManualColorBlit =
             needManualColorBlit || (sourceSRGB && mFunctions->isAtMostGL(gl::Version(4, 3)));
     }
@@ -329,13 +329,12 @@ Error FramebufferGL::blit(ContextImpl *context,
         needManualColorBlit =
             needManualColorBlit || (destSRGB && mFunctions->isAtMostGL(gl::Version(4, 1)));
     }
-    }
 
     // Enable FRAMEBUFFER_SRGB if needed
     mStateManager->setFramebufferSRGBEnabledForFramebuffer(true, this);
 
     GLenum blitMask = mask;
-    if (needManualColorBlit && (mask & GL_COLOR_BUFFER_BIT))
+    if (needManualColorBlit && (mask & GL_COLOR_BUFFER_BIT) && readAttachmentSamples <= 1)
     {
         ANGLE_TRY(mBlitter->blitColorBufferWithShader(sourceFramebuffer, destFramebuffer,
                                                       sourceArea, destArea, filter));