Allow DrawingBuffer to present to a bitmap.

Source/core/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 158 matching lines @@
     return textureId;
 }
 
 WebKit::WebGraphicsContext3D* DrawingBuffer::context()
 {
     if (!m_context)
         return 0;
     return m_context->webContext();
 }
 
-bool DrawingBuffer::prepareMailbox(WebKit::WebExternalTextureMailbox* outMailbox)
+bool DrawingBuffer::prepareMailbox(WebKit::WebExternalTextureMailbox* outMailbox, bool bitmap)
 {
     if (!m_context || !m_contentsChanged || !m_lastColorBuffer)
         return false;
 
     m_context->makeContextCurrent();
 
     // Resolve the multisampled buffer into the texture referenced by m_lastColorBuffer mailbox.
     if (multisample())
         commit();
 
+    if (bitmap) {
+        SkBitmap* bitmap = &m_lastColorBuffer->mailbox.bitmap;
+        m_context->bindFramebuffer(GraphicsContext3D::FRAMEBUFFER, m_fbo);
+        if (bitmap->width() != size().width()
+            || bitmap->height() != size().height()) {
+            bitmap->setConfig(SkBitmap::kARGB_8888_Config, size().width(), size().height(), 0);
+            bitmap->allocPixels();
+        }
+        m_lastColorBuffer->mailbox.size = size();
+
+        SkAutoLockPixels bitmapLock(*bitmap);
+
+        unsigned char* pixels = static_cast<unsigned char*>(bitmap->getPixels());
+        m_context->readPixels(0, 0, size().width(), size().height(), GraphicsContext3D::RGBA, GraphicsContext3D::UNSIGNED_BYTE, pixels);

[Ken Russell (switch to Gerrit), 2013/06/27 13:41:02]

We'd better be careful that the user hasn't set the unpack alignment to 8.

+        for (int i = 0; i < size().width() * size().height() * 4; i += 4)
+            swap(pixels[i + 0], pixels[i + 2]);

[Ken Russell (switch to Gerrit), 2013/06/27 13:41:02]

I'm pretty sure this needs to be conditional depending on the platform. See
GraphicsContext3D::paintRenderingResultsToImageData . If there's a possibility
for code reuse that would be better.

+
+        if (m_attributes.alpha && !m_attributes.premultipliedAlpha) {
+            for (int i = 0; i < size().width() * size().height() * 4; i += 4) {
+                pixels[i + 0] = std::min(255, pixels[i + 0] * pixels[i + 3] / 255);
+                pixels[i + 1] = std::min(255, pixels[i + 1] * pixels[i + 3] / 255);
+                pixels[i + 2] = std::min(255, pixels[i + 2] * pixels[i + 3] / 255);
+            }
+        }
+    }
+
     // We must restore the texture binding since creating new textures,
     // consuming and producing mailboxes changes it.
     ScopedTextureUnit0BindingRestorer restorer(m_context.get(), m_activeTextureUnit, m_texture2DBinding);
 
     // First try to recycle an old buffer.
     RefPtr<MailboxInfo> nextFrontColorBuffer = getRecycledMailbox();
 
     // No buffer available to recycle, create a new one.
     if (!nextFrontColorBuffer) {
         unsigned newColorBuffer = createColorTexture(m_size);
         // Bad things happened, abandon ship.
         if (!newColorBuffer)
             return false;
 
         nextFrontColorBuffer = createNewMailbox(newColorBuffer);
     }
 
     if (m_preserveDrawingBuffer == Discard) {
         m_colorBuffer = nextFrontColorBuffer->textureId;
         swap(nextFrontColorBuffer, m_lastColorBuffer);
         // 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(GraphicsContext3D::FRAMEBUFFER, m_fbo);
         m_context->framebufferTexture2D(GraphicsContext3D::FRAMEBUFFER, GraphicsContext3D::COLOR_ATTACHMENT0, GraphicsContext3D::TEXTURE_2D, m_colorBuffer, 0);
     } else {
         Extensions3D* extensions = m_context->getExtensions();
         extensions->copyTextureCHROMIUM(GraphicsContext3D::TEXTURE_2D, m_colorBuffer, nextFrontColorBuffer->textureId, 0, GraphicsContext3D::RGBA, GraphicsContext3D::UNSIGNED_BYTE);
+        SkBitmap nextBitmap = nextFrontColorBuffer->mailbox.bitmap;
+        nextFrontColorBuffer->mailbox.bitmap = m_lastColorBuffer->mailbox.bitmap;
+        nextFrontColorBuffer->mailbox.size = m_lastColorBuffer->mailbox.size;
+        m_lastColorBuffer->mailbox.bitmap = nextBitmap;
     }
 
     if (multisample() && !m_framebufferBinding)
         bind();
     else
         restoreFramebufferBinding();
 
     m_contentsChanged = false;
 
     context()->bindTexture(GraphicsContext3D::TEXTURE_2D, nextFrontColorBuffer->textureId);
     context()->produceTextureCHROMIUM(GraphicsContext3D::TEXTURE_2D, nextFrontColorBuffer->mailbox.name);
     context()->flush();
     m_context->markLayerComposited();
 
     *outMailbox = nextFrontColorBuffer->mailbox;
+
     m_frontColorBuffer = nextFrontColorBuffer->textureId;
     return true;
 }
 
 void DrawingBuffer::mailboxReleased(const WebKit::WebExternalTextureMailbox& mailbox)
 {
     for (size_t i = 0; i < m_textureMailboxes.size(); i++) {
-         RefPtr<MailboxInfo> mailboxInfo = m_textureMailboxes[i];
-         if (!memcmp(mailboxInfo->mailbox.name, mailbox.name, sizeof(mailbox.name))) {
-             mailboxInfo->mailbox.syncPoint = mailbox.syncPoint;
-             m_recycledMailboxes.append(mailboxInfo.release());
-             return;
-         }
+        RefPtr<MailboxInfo> mailboxInfo = m_textureMailboxes[i];
+        if (!memcmp(mailboxInfo->mailbox.name, mailbox.name, sizeof(mailbox.name))) {
+            mailboxInfo->mailbox.syncPoint = mailbox.syncPoint;
+            mailboxInfo->mailbox.bitmap = mailbox.bitmap;
+            m_recycledMailboxes.append(mailboxInfo.release());
+            return;
+        }
      }
      ASSERT_NOT_REACHED();
 }
 
 PassRefPtr<DrawingBuffer::MailboxInfo> DrawingBuffer::getRecycledMailbox()
 {
     if (!m_context || m_recycledMailboxes.isEmpty())
         return PassRefPtr<MailboxInfo>();
 
     RefPtr<MailboxInfo> mailboxInfo = m_recycledMailboxes.last().release();
@@ skipping 557 matching lines @@
 
 void DrawingBuffer::bind()
 {
     if (!m_context)
         return;
 
     m_context->bindFramebuffer(GraphicsContext3D::FRAMEBUFFER, m_multisampleFBO ? m_multisampleFBO : m_fbo);
 }
 
 } // namespace WebCore