Add GL_CHROMIUM_screen_space_antialiasing to support alternative AA

Source/platform/graphics/gpu/DrawingBuffer.cpp

 /*
  * Copyright (c) 2010, Google Inc. All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
  * modification, are permitted provided that the following conditions are
  * met:
  *
  *     * Redistributions of source code must retain the above copyright
  * notice, this list of conditions and the following disclaimer.
  *     * Redistributions in binary form must reproduce the above
@@ skipping 416 matching lines @@
         m_internalRenderbufferFormat = GL_RGB8_OES;
     }
 
     m_context->getIntegerv(GL_MAX_TEXTURE_SIZE, &m_maxTextureSize);
 
     int maxSampleCount = 0;
     m_multisampleMode = None;
     if (m_requestedAttributes.antialias && m_multisampleExtensionSupported) {
         m_context->getIntegerv(GL_MAX_SAMPLES_ANGLE, &maxSampleCount);
         m_multisampleMode = ExplicitResolve;
-        if (m_extensionsUtil->supportsExtension("GL_EXT_multisampled_render_to_texture"))
+        if (m_extensionsUtil->supportsExtension("GL_EXT_multisampled_render_to_texture")) {
             m_multisampleMode = ImplicitResolve;
+        }
+        if (m_extensionsUtil->supportsExtension("GL_INTEL_framebuffer_CMAA")) {

[bajones, 2015/08/19 16:26:44]

Nit: This should be an `else if`

[Ken Russell (switch to Gerrit), 2015/08/19 17:56:18]

Or does the Intel hardware supporting INTEL_framebuffer_CMAA support both
extensions? Is CMAA preferred by Intel?

+            m_multisampleMode = INTELCMAAResolve;

[piman, 2015/08/19 16:36:51]

drive-by nit: CMAA is not multisampling, maybe rename m_multisampleMode into
m_antiAliasingMode, and then ImplicitResolve/ExplicitResolve into
MSAAImplicitResolve/MSAAExplicitResolve ?

[Ken Russell (switch to Gerrit), 2015/08/19 17:56:18]

I like Antoine's suggestion. Could you please make that change?

+        }
     }
     m_sampleCount = std::min(4, maxSampleCount);
 
     m_fbo = m_context->createFramebuffer();
 
     m_context->bindFramebuffer(GL_FRAMEBUFFER, m_fbo);
     m_colorBuffer.textureId = createColorTexture();
     if (m_multisampleMode == ImplicitResolve)
         m_context->framebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_colorBuffer.textureId, 0, m_sampleCount);
     else
@@ skipping 359 matching lines @@
         int width = m_size.width();
         int height = m_size.height();
         // Use NEAREST, because there is no scale performed during the blit.
         m_context->blitFramebufferCHROMIUM(0, 0, width, height, 0, 0, width, height, GL_COLOR_BUFFER_BIT, GL_NEAREST);
 
         if (m_scissorEnabled)
             m_context->enable(GL_SCISSOR_TEST);
     }
 
     m_context->bindFramebuffer(GL_FRAMEBUFFER, m_fbo);
+    if (m_multisampleMode == INTELCMAAResolve) {
+        // Apply CMAA(Conservative Morphological Anti-Aliasing) algorithm to the color buffer of m_fbo.
+        // Reference: https://software.intel.com/en-us/articles/conservative-morphological-anti-aliasing-cmaa
+        m_context->applyFramebufferAttachmentCMAAINTEL();
+    }
     m_contentsChangeCommitted = true;
 }
 
 void DrawingBuffer::restoreFramebufferBindings()
 {
     if (m_drawFramebufferBinding && m_readFramebufferBinding) {
         if (m_drawFramebufferBinding == m_readFramebufferBinding) {
             m_context->bindFramebuffer(GL_FRAMEBUFFER, m_readFramebufferBinding);
         } else {
             m_context->bindFramebuffer(GL_READ_FRAMEBUFFER, m_readFramebufferBinding);
@@ skipping 183 matching lines @@
 void DrawingBuffer::deleteChromiumImageForTexture(TextureInfo* info)
 {
     if (info->imageId) {
         m_context->releaseTexImage2DCHROMIUM(GL_TEXTURE_2D, info->imageId);
         m_context->destroyImageCHROMIUM(info->imageId);
         info->imageId = 0;
     }
 }
 
 } // namespace blink