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 136 matching lines @@
     , m_discardFramebufferSupported(discardFramebufferSupported)
     , m_fbo(0)
     , m_depthStencilBuffer(0)
     , m_depthBuffer(0)
     , m_stencilBuffer(0)
     , m_multisampleFBO(0)
     , m_multisampleColorBuffer(0)
     , m_contentsChanged(true)
     , m_contentsChangeCommitted(false)
     , m_bufferClearNeeded(false)
-    , m_multisampleMode(None)
+    , m_antiAliasingMode(None)
     , m_internalColorFormat(0)
     , m_colorFormat(0)
     , m_internalRenderbufferFormat(0)
     , m_maxTextureSize(0)
     , m_sampleCount(0)
     , m_packAlignment(4)
     , m_destructionInProgress(false)
     , m_isHidden(false)
     , m_filterQuality(kLow_SkFilterQuality)
 {
@@ skipping 74 matching lines @@
         // 2. The compositor begins the frame.
         // 3. Javascript makes a context lost using WEBGL_lose_context extension.
         // 4. Here.
         return false;
     }
     ASSERT(!m_isHidden);
     if (!m_contentsChanged)
         return false;
 
     // Resolve the multisampled buffer into m_colorBuffer texture.
-    if (m_multisampleMode != None)
+    if (m_antiAliasingMode != None)
         commit();
 
     if (bitmap) {
         bitmap->setSize(size());
 
         unsigned char* pixels = bitmap->pixels();
         bool needPremultiply = m_actualAttributes.alpha && !m_actualAttributes.premultipliedAlpha;
         WebGLImageConversion::AlphaOp op = needPremultiply ? WebGLImageConversion::AlphaDoPremultiply : WebGLImageConversion::AlphaDoNothing;
         if (pixels)
             readBackFramebuffer(pixels, size().width(), size().height(), ReadbackSkia, op);
@@ skipping 18 matching lines @@
         frontColorBufferMailbox = createNewMailbox(newTexture);
     }
 
     if (m_preserveDrawingBuffer == Discard) {
         std::swap(frontColorBufferMailbox->textureInfo, m_colorBuffer);
         // It appears safe to overwrite the context's framebuffer binding in the Discard case since there will always be a
         // WebGLRenderingContext::clearIfComposited() call made before the next draw call which restores the framebuffer binding.
         // If this stops being true at some point, we should track the current framebuffer binding in the DrawingBuffer and restore
         // it after attaching the new back buffer here.
         m_context->bindFramebuffer(GL_FRAMEBUFFER, m_fbo);
-        if (m_multisampleMode == ImplicitResolve)
+        if (m_antiAliasingMode == MSAAImplicitResolve)
             m_context->framebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_colorBuffer.textureId, 0, m_sampleCount);
         else
             m_context->framebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_colorBuffer.textureId, 0);
 
         if (m_discardFramebufferSupported) {
             // Explicitly discard framebuffer to save GPU memory bandwidth for tile-based GPU arch.
             const WGC3Denum attachments[3] = { GL_COLOR_ATTACHMENT0, GL_DEPTH_ATTACHMENT, GL_STENCIL_ATTACHMENT};
             m_context->discardFramebufferEXT(GL_FRAMEBUFFER, 3, attachments);
         }
     } else {
@@ skipping 121 matching lines @@
         m_internalRenderbufferFormat = GL_RGBA8_OES;
     } else {
         m_internalColorFormat = GL_RGB;
         m_colorFormat = GL_RGB;
         m_internalRenderbufferFormat = GL_RGB8_OES;
     }
 
     m_context->getIntegerv(GL_MAX_TEXTURE_SIZE, &m_maxTextureSize);
 
     int maxSampleCount = 0;
-    m_multisampleMode = None;
+    m_antiAliasingMode = 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"))
-            m_multisampleMode = ImplicitResolve;
+        m_antiAliasingMode = MSAAExplicitResolve;
+        if (m_extensionsUtil->supportsExtension("GL_EXT_multisampled_render_to_texture")) {
+            m_antiAliasingMode = MSAAImplicitResolve;
+        } else if (m_extensionsUtil->supportsExtension("GL_CHROMIUM_screen_space_antialiasing")) {
+            m_antiAliasingMode = ScreenSpaceAntialiasing;
+        }
     }
     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)
+    if (m_antiAliasingMode == MSAAImplicitResolve)
         m_context->framebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_colorBuffer.textureId, 0, m_sampleCount);
     else
         m_context->framebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_colorBuffer.textureId, 0);
     createSecondaryBuffers();
     // We first try to initialize everything with the requested attributes.
     if (!reset(size))
         return false;
     // If that succeeds, we then see what we actually got and update our actual attributes to reflect that.
     m_actualAttributes = m_requestedAttributes;
     if (m_requestedAttributes.alpha) {
@@ skipping 18 matching lines @@
         return false;
     }
 
     return true;
 }
 
 bool DrawingBuffer::copyToPlatformTexture(WebGraphicsContext3D* context, Platform3DObject texture, GLenum internalFormat,
     GLenum destType, GLint level, bool premultiplyAlpha, bool flipY, SourceDrawingBuffer sourceBuffer)
 {
     if (m_contentsChanged) {
-        if (m_multisampleMode != None) {
+        if (m_antiAliasingMode != None) {
             commit();
             restoreFramebufferBindings();
         }
         m_context->flush();
     }
 
     if (!Extensions3DUtil::canUseCopyTextureCHROMIUM(GL_TEXTURE_2D, internalFormat, destType, level))
         return false;
 
     // Contexts may be in a different share group. We must transfer the texture through a mailbox first
@@ skipping 117 matching lines @@
     m_context->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_MIN_FILTER, GL_LINEAR);
     m_context->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_S, GL_CLAMP_TO_EDGE);
     m_context->texParameteri(GL_TEXTURE_2D, GL_TEXTURE_WRAP_T, GL_CLAMP_TO_EDGE);
 
     return offscreenColorTexture;
 }
 
 void DrawingBuffer::createSecondaryBuffers()
 {
     // create a multisample FBO
-    if (m_multisampleMode == ExplicitResolve) {
+    if (m_antiAliasingMode == MSAAExplicitResolve) {
         m_multisampleFBO = m_context->createFramebuffer();
         m_context->bindFramebuffer(GL_FRAMEBUFFER, m_multisampleFBO);
         m_multisampleColorBuffer = m_context->createRenderbuffer();
     }
 }
 
 bool DrawingBuffer::resizeFramebuffer(const IntSize& size)
 {
     // resize regular FBO
     m_context->bindFramebuffer(GL_FRAMEBUFFER, m_fbo);
 
     m_context->bindTexture(GL_TEXTURE_2D, m_colorBuffer.textureId);
 
     allocateTextureMemory(&m_colorBuffer, size);
 
-    if (m_multisampleMode == ImplicitResolve)
+    if (m_antiAliasingMode == MSAAImplicitResolve)
         m_context->framebufferTexture2DMultisampleEXT(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_colorBuffer.textureId, 0, m_sampleCount);
     else
         m_context->framebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_TEXTURE_2D, m_colorBuffer.textureId, 0);
 
     m_context->bindTexture(GL_TEXTURE_2D, 0);
 
-    if (m_multisampleMode != ExplicitResolve)
+    if (m_antiAliasingMode != MSAAExplicitResolve)
         resizeDepthStencil(size);
     if (m_context->checkFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
         return false;
 
     return true;
 }
 
 bool DrawingBuffer::resizeMultisampleFramebuffer(const IntSize& size)
 {
-    if (m_multisampleMode == ExplicitResolve) {
+    if (m_antiAliasingMode == MSAAExplicitResolve) {
         m_context->bindFramebuffer(GL_FRAMEBUFFER, m_multisampleFBO);
 
         m_context->bindRenderbuffer(GL_RENDERBUFFER, m_multisampleColorBuffer);
         m_context->renderbufferStorageMultisampleCHROMIUM(GL_RENDERBUFFER, m_sampleCount, m_internalRenderbufferFormat, size.width(), size.height());
 
         if (m_context->getError() == GL_OUT_OF_MEMORY)
             return false;
 
         m_context->framebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, GL_RENDERBUFFER, m_multisampleColorBuffer);
         resizeDepthStencil(size);
         if (m_context->checkFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
             return false;
     }
 
     return true;
 }
 
 void DrawingBuffer::resizeDepthStencil(const IntSize& size)
 {
     if (!m_requestedAttributes.depth && !m_requestedAttributes.stencil)
         return;
 
     if (m_packedDepthStencilExtensionSupported) {
         if (!m_depthStencilBuffer)
             m_depthStencilBuffer = m_context->createRenderbuffer();
         m_context->bindRenderbuffer(GL_RENDERBUFFER, m_depthStencilBuffer);
-        if (m_multisampleMode == ImplicitResolve)
+        if (m_antiAliasingMode == MSAAImplicitResolve)
             m_context->renderbufferStorageMultisampleEXT(GL_RENDERBUFFER, m_sampleCount, GL_DEPTH24_STENCIL8_OES, size.width(), size.height());
-        else if (m_multisampleMode == ExplicitResolve)
+        else if (m_antiAliasingMode == MSAAExplicitResolve)
             m_context->renderbufferStorageMultisampleCHROMIUM(GL_RENDERBUFFER, m_sampleCount, GL_DEPTH24_STENCIL8_OES, size.width(), size.height());
         else
             m_context->renderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8_OES, size.width(), size.height());
         m_context->framebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, m_depthStencilBuffer);
         m_context->framebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, m_depthStencilBuffer);
     } else {
         if (m_requestedAttributes.depth) {
             if (!m_depthBuffer)
                 m_depthBuffer = m_context->createRenderbuffer();
             m_context->bindRenderbuffer(GL_RENDERBUFFER, m_depthBuffer);
-            if (m_multisampleMode == ImplicitResolve)
+            if (m_antiAliasingMode == MSAAImplicitResolve)
                 m_context->renderbufferStorageMultisampleEXT(GL_RENDERBUFFER, m_sampleCount, GL_DEPTH_COMPONENT16, size.width(), size.height());
-            else if (m_multisampleMode == ExplicitResolve)
+            else if (m_antiAliasingMode == MSAAExplicitResolve)
                 m_context->renderbufferStorageMultisampleCHROMIUM(GL_RENDERBUFFER, m_sampleCount, GL_DEPTH_COMPONENT16, size.width(), size.height());
             else
                 m_context->renderbufferStorage(GL_RENDERBUFFER, GL_DEPTH_COMPONENT16, size.width(), size.height());
             m_context->framebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_ATTACHMENT, GL_RENDERBUFFER, m_depthBuffer);
         }
         if (m_requestedAttributes.stencil) {
             if (!m_stencilBuffer)
                 m_stencilBuffer = m_context->createRenderbuffer();
             m_context->bindRenderbuffer(GL_RENDERBUFFER, m_stencilBuffer);
-            if (m_multisampleMode == ImplicitResolve)
+            if (m_antiAliasingMode == MSAAImplicitResolve)
                 m_context->renderbufferStorageMultisampleEXT(GL_RENDERBUFFER, m_sampleCount, GL_STENCIL_INDEX8, size.width(), size.height());
-            else if (m_multisampleMode == ExplicitResolve)
+            else if (m_antiAliasingMode == MSAAExplicitResolve)
                 m_context->renderbufferStorageMultisampleCHROMIUM(GL_RENDERBUFFER, m_sampleCount, GL_STENCIL_INDEX8, size.width(), size.height());
             else
                 m_context->renderbufferStorage(GL_RENDERBUFFER, GL_STENCIL_INDEX8, size.width(), size.height());
             m_context->framebufferRenderbuffer(GL_FRAMEBUFFER, GL_STENCIL_ATTACHMENT, GL_RENDERBUFFER, m_stencilBuffer);
         }
     }
     m_context->bindRenderbuffer(GL_RENDERBUFFER, 0);
 }
 
 
@@ skipping 87 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_antiAliasingMode == ScreenSpaceAntialiasing) {
+        m_context->applyScreenSpaceAntialiasingCHROMIUM();
+    }
     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);
             m_context->bindFramebuffer(GL_DRAW_FRAMEBUFFER, m_drawFramebufferBinding);
         }
         return;
     }
     if (!m_drawFramebufferBinding && !m_readFramebufferBinding) {
         bind(GL_FRAMEBUFFER);
         return;
     }
     if (!m_drawFramebufferBinding) {
         bind(GL_DRAW_FRAMEBUFFER);
         m_context->bindFramebuffer(GL_READ_FRAMEBUFFER, m_readFramebufferBinding);
     } else {
         bind(GL_READ_FRAMEBUFFER);
         m_context->bindFramebuffer(GL_DRAW_FRAMEBUFFER, m_drawFramebufferBinding);
     }
 }
 
 bool DrawingBuffer::multisample() const
 {
-    return m_multisampleMode != None;
+    return m_antiAliasingMode != None;
 }
 
 void DrawingBuffer::bind(GLenum target)
 {
     if (target != GL_READ_FRAMEBUFFER)
         m_context->bindFramebuffer(target, m_multisampleFBO ? m_multisampleFBO : m_fbo);
     else
         m_context->bindFramebuffer(target, m_fbo);
 }
 
@@ skipping 153 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