Generate INVALID_OPERATION if feedback loops exist in CopyTex{Sub}Image2D.

gpu/command_buffer/service/gles2_cmd_decoder.cc

Index: gpu/command_buffer/service/gles2_cmd_decoder.cc
diff --git a/gpu/command_buffer/service/gles2_cmd_decoder.cc b/gpu/command_buffer/service/gles2_cmd_decoder.cc
index 1213e616f2e1638adbfe653b2200607b04e69860..edf835ff0cac292c74b45f39adc682ef1f2e30e2 100644
--- a/gpu/command_buffer/service/gles2_cmd_decoder.cc
+++ b/gpu/command_buffer/service/gles2_cmd_decoder.cc
@@ -1181,6 +1181,10 @@ class GLES2DecoderImpl : public GLES2Decoder,
   // attached. Generates GL error if not.
   bool CheckBoundReadFramebufferColorAttachment(const char* func_name);
 
+  // Check that the currently bound read framebuffer's color image
+  // isn't the target texture of the glCopyTex{Sub}Image2D.
+  bool FormsTextureCopyingFeedbackLoop(TextureRef* texture, GLint level);
+
   // Check if a framebuffer meets our requirements.
   bool CheckFramebufferValid(
       Framebuffer* framebuffer,
@@ -3232,6 +3236,20 @@ bool GLES2DecoderImpl::CheckBoundReadFramebufferColorAttachment(
   return true;
 }
 
+bool GLES2DecoderImpl::FormsTextureCopyingFeedbackLoop(
+    TextureRef* texture, GLint level) {
+  Framebuffer* framebuffer = features().chromium_framebuffer_multisample ?
+      framebuffer_state_.bound_read_framebuffer.get() :
+      framebuffer_state_.bound_draw_framebuffer.get();
+  if (!framebuffer)
+    return false;
+  const Framebuffer::Attachment* attachment = framebuffer->GetAttachment(
+      GL_COLOR_ATTACHMENT0);
+  if (!attachment)
+    return false;
+  return attachment->FormsFeedbackLoop(texture, level);
+}
+
 gfx::Size GLES2DecoderImpl::GetBoundReadFrameBufferSize() {
   Framebuffer* framebuffer =
       GetFramebufferInfoForTarget(GL_READ_FRAMEBUFFER_EXT);
@@ -8595,6 +8613,12 @@ void GLES2DecoderImpl::DoCopyTexImage2D(
     return;
   }
 
+  if (FormsTextureCopyingFeedbackLoop(texture_ref, level)) {
+    LOCAL_SET_GL_ERROR(
+        GL_INVALID_OPERATION, "glCopyTexImage2D", "feedback loops");

[bajones, 2014/10/13 22:22:09]

I feel like the error message here and below could be a little more explicit to
help confused developers. Maybe something like "Source and destination texture
are the same"? 

[Zhenyao Mo, 2014/10/13 22:31:40]

Done.

+    return;
+  }
+
   if (!CheckBoundFramebuffersValid("glCopyTexImage2D")) {
     return;
   }
@@ -8713,6 +8737,12 @@ void GLES2DecoderImpl::DoCopyTexSubImage2D(
     return;
   }
 
+  if (FormsTextureCopyingFeedbackLoop(texture_ref, level)) {
+    LOCAL_SET_GL_ERROR(
+        GL_INVALID_OPERATION, "glCopyTexSubImage2D", "feedback loops");
+    return;
+  }
+
   if (!CheckBoundFramebuffersValid("glCopyTexSubImage2D")) {
     return;
   }