gpu, cmaa: add glApplyScreenSpaceAntialiasingCHROMIUM unittests

gpu/command_buffer/service/gles2_cmd_decoder.cc

 // Copyright (c) 2012 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "gpu/command_buffer/service/gles2_cmd_decoder.h"
 
 #include <limits.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
@@ skipping 16700 matching lines @@
     LOCAL_SET_GL_ERROR(
         GL_INVALID_OPERATION,
         "glCreateAndConsumeTextureCHROMIUM", "invalid target");
     return;
   }
 
   texture_ref = texture_manager()->Consume(client_id, texture);
 }
 
 void GLES2DecoderImpl::DoApplyScreenSpaceAntialiasingCHROMIUM() {
+  Framebuffer* bound_framebuffer =
+      GetFramebufferInfoForTarget(GL_DRAW_FRAMEBUFFER);
+  if (!bound_framebuffer) {
+    LOCAL_SET_GL_ERROR(GL_INVALID_OPERATION,
+                       "glApplyScreenSpaceAntialiasingCHROMIUM",
+                       "no bound framebuffer object");
+    return;
+  }

[piman, 2016/10/20 18:36:17]

Can you update
gpu/GLES2/extensions/CHROMIUM/CHROMIUM_screen_space_antialiasing.txt to document
this new restriction?

What would be required to support it on the main framebuffer? In the future we
may want to do direct-to-main-framebuffer rendering for skia.

[dshwang, 2016/10/20 19:12:18]

good question.

https://cs.chromium.org/chromium/src/gpu/GLES2/extensions/CHROMIUM/CHROMIUM_s...

CHROMIUM_screen_space_antialiasing.txt already implies the extensions doesn't
work after glBindFramebuffer(0).

In fact, chromium implementation can work even after calling
glBindFramebuffer(0), because offscreen GLES2 decoder has FBO as default
framebuffer, rather than EGLSurface or something.

In summary, I add this restriction so that
CHROMIUM_screen_space_antialiasing.txt has simple explanation.

As far as I know, skia ganesh creates its own default FBO, rather than using
glBindFramebuffer(0), because it makes it efficient to do
canvas.draw(another_canvas).
When we support cmaa in skia and skia really need glBindFramebuffer(0), I will
change hear to support default FBO of offscreen GLES2 decoder, while it doesn't
support default FBO of onscreen GLES2 decoder tho.

+
   // Apply CMAA(Conservative Morphological Anti-Aliasing) algorithm to the
   // color attachments of currently bound draw framebuffer.
   // Reference GL_INTEL_framebuffer_CMAA for details.
   // Use platform version if available.
   if (!feature_info_->feature_flags()
            .use_chromium_screen_space_antialiasing_via_shaders) {
     glApplyFramebufferAttachmentCMAAINTEL();
   } else {
     // Defer initializing the CopyTextureCHROMIUMResourceManager until it is
     // needed because it takes ??s of milliseconds to initialize.
     if (!apply_framebuffer_attachment_cmaa_intel_.get()) {
       LOCAL_COPY_REAL_GL_ERRORS_TO_WRAPPER(
           "glApplyFramebufferAttachmentCMAAINTEL");
       apply_framebuffer_attachment_cmaa_intel_.reset(
           new ApplyFramebufferAttachmentCMAAINTELResourceManager());
       apply_framebuffer_attachment_cmaa_intel_->Initialize(this);
       RestoreCurrentFramebufferBindings();
       if (LOCAL_PEEK_GL_ERROR("glApplyFramebufferAttachmentCMAAINTEL") !=
           GL_NO_ERROR)
         return;
     }
     apply_framebuffer_attachment_cmaa_intel_
-        ->ApplyFramebufferAttachmentCMAAINTEL(
-            this, GetFramebufferInfoForTarget(GL_DRAW_FRAMEBUFFER));
+        ->ApplyFramebufferAttachmentCMAAINTEL(this, bound_framebuffer);
   }
 }
 
 void GLES2DecoderImpl::DoInsertEventMarkerEXT(
     GLsizei length, const GLchar* marker) {
   if (!marker) {
     marker = "";
   }
   debug_marker_manager_.SetMarker(
       length ? std::string(marker, length) : std::string(marker));
@@ skipping 1852 matching lines @@
 }
 
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.
 #include "base/macros.h"
 #include "gpu/command_buffer/service/gles2_cmd_decoder_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu