DrawingBuffer: Clean up GL state restoration

third_party/WebKit/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 41 matching lines @@
 #include "wtf/typed_arrays/ArrayBufferContents.h"
 #include <algorithm>
 #include <memory>
 
 namespace blink {
 
 namespace {
 
 const float s_resourceAdjustedRatio = 0.5;
 
-class ScopedTextureUnit0BindingRestorer {
-  STACK_ALLOCATED();
-  WTF_MAKE_NONCOPYABLE(ScopedTextureUnit0BindingRestorer);
-
- public:
-  ScopedTextureUnit0BindingRestorer(gpu::gles2::GLES2Interface* gl,
-                                    GLenum activeTextureUnit,
-                                    GLuint textureUnitZeroId)
-      : m_gl(gl),
-        m_oldActiveTextureUnit(activeTextureUnit),
-        m_oldTextureUnitZeroId(textureUnitZeroId) {
-    m_gl->ActiveTexture(GL_TEXTURE0);
-  }
-  ~ScopedTextureUnit0BindingRestorer() {
-    m_gl->BindTexture(GL_TEXTURE_2D, m_oldTextureUnitZeroId);
-    m_gl->ActiveTexture(m_oldActiveTextureUnit);
-  }
-
- private:
-  gpu::gles2::GLES2Interface* m_gl;
-  GLenum m_oldActiveTextureUnit;
-  GLuint m_oldTextureUnitZeroId;
-};
-
 static bool shouldFailDrawingBufferCreationForTesting = false;
 
 }  // namespace
 
 PassRefPtr<DrawingBuffer> DrawingBuffer::create(
     std::unique_ptr<WebGraphicsContext3DProvider> contextProvider,
+    Client* client,
     const IntSize& size,
     bool premultipliedAlpha,
     bool wantAlphaChannel,
     bool wantDepthBuffer,
     bool wantStencilBuffer,
     bool wantAntialiasing,
     PreserveDrawingBuffer preserve,
     WebGLVersion webGLVersion,
     ChromiumImageUsage chromiumImageUsage) {
   ASSERT(contextProvider);
@@ skipping 26 matching lines @@
     else
       extensionsUtil->ensureExtensionEnabled(
           "GL_EXT_multisampled_render_to_texture");
   }
   bool discardFramebufferSupported =
       extensionsUtil->supportsExtension("GL_EXT_discard_framebuffer");
   if (discardFramebufferSupported)
     extensionsUtil->ensureExtensionEnabled("GL_EXT_discard_framebuffer");
 
   RefPtr<DrawingBuffer> drawingBuffer = adoptRef(new DrawingBuffer(
-      std::move(contextProvider), std::move(extensionsUtil),
+      std::move(contextProvider), std::move(extensionsUtil), client,
       discardFramebufferSupported, wantAlphaChannel, premultipliedAlpha,
       preserve, webGLVersion, wantDepthBuffer, wantStencilBuffer,
       chromiumImageUsage));
   if (!drawingBuffer->initialize(size, multisampleSupported)) {
     drawingBuffer->beginDestruction();
     return PassRefPtr<DrawingBuffer>();
   }
   return drawingBuffer.release();
 }
 
 void DrawingBuffer::forceNextDrawingBufferCreationToFail() {
   shouldFailDrawingBufferCreationForTesting = true;
 }
 
 DrawingBuffer::DrawingBuffer(
     std::unique_ptr<WebGraphicsContext3DProvider> contextProvider,
     std::unique_ptr<Extensions3DUtil> extensionsUtil,
+    Client* client,
     bool discardFramebufferSupported,
     bool wantAlphaChannel,
     bool premultipliedAlpha,
     PreserveDrawingBuffer preserve,
     WebGLVersion webGLVersion,
     bool wantDepth,
     bool wantStencil,
     ChromiumImageUsage chromiumImageUsage)
-    : m_preserveDrawingBuffer(preserve),
+    : m_client(client),
+      m_preserveDrawingBuffer(preserve),
       m_webGLVersion(webGLVersion),
       m_contextProvider(std::move(contextProvider)),
       m_gl(m_contextProvider->contextGL()),
       m_extensionsUtil(std::move(extensionsUtil)),
       m_discardFramebufferSupported(discardFramebufferSupported),
       m_wantAlphaChannel(wantAlphaChannel),
       m_premultipliedAlpha(premultipliedAlpha),
       m_softwareRendering(m_contextProvider->isSoftwareRendering()),
       m_wantDepth(wantDepth),
       m_wantStencil(wantStencil),
       m_chromiumImageUsage(chromiumImageUsage) {
-  memset(m_colorMask, 0, 4 * sizeof(GLboolean));
-  memset(m_clearColor, 0, 4 * sizeof(GLfloat));
   // Used by browser tests to detect the use of a DrawingBuffer.
   TRACE_EVENT_INSTANT0("test_gpu", "DrawingBufferCreation",
                        TRACE_EVENT_SCOPE_GLOBAL);
 }
 
 DrawingBuffer::~DrawingBuffer() {
   DCHECK(m_destructionInProgress);
   m_layer.reset();
   m_contextProvider.reset();
 }
@@ skipping 33 matching lines @@
 
 void DrawingBuffer::setFilterQuality(SkFilterQuality filterQuality) {
   if (m_filterQuality != filterQuality) {
     m_filterQuality = filterQuality;
     if (m_layer)
       m_layer->setNearestNeighbor(filterQuality == kNone_SkFilterQuality);
   }
 }
 
 bool DrawingBuffer::requiresAlphaChannelToBePreserved() {
-  return !m_drawFramebufferBinding &&
+  return m_client->DrawingBufferClientIsBoundForDraw() &&
          defaultBufferRequiresAlphaChannelToBePreserved();
 }
 
 bool DrawingBuffer::defaultBufferRequiresAlphaChannelToBePreserved() {
   if (wantExplicitResolve()) {
     return !m_wantAlphaChannel &&
            getMultisampledRenderbufferFormat() == GL_RGBA8_OES;
   }
 
   bool rgbEmulation =
@@ skipping 15 matching lines @@
     DCHECK(recycled.size == m_size);
     return std::move(recycled.bitmap);
   }
 
   return Platform::current()->allocateSharedBitmap(m_size);
 }
 
 bool DrawingBuffer::PrepareTextureMailbox(
     cc::TextureMailbox* outMailbox,
     std::unique_ptr<cc::SingleReleaseCallback>* outReleaseCallback) {
+  ScopedStateRestorer scopedStateRestorer(this);
   bool forceGpuResult = false;
   return prepareTextureMailboxInternal(outMailbox, outReleaseCallback,
                                        forceGpuResult);
 }
 
 bool DrawingBuffer::prepareTextureMailboxInternal(
     cc::TextureMailbox* outMailbox,
     std::unique_ptr<cc::SingleReleaseCallback>* outReleaseCallback,
     bool forceGpuResult) {
   if (m_destructionInProgress) {
@@ skipping 14 matching lines @@
   if (m_gl->GetGraphicsResetStatusKHR() != GL_NO_ERROR)
     return false;
 
   TRACE_EVENT0("blink,rail", "DrawingBuffer::prepareMailbox");
 
   if (m_newMailboxCallback)
     (*m_newMailboxCallback)();
 
   // Resolve the multisampled buffer into m_backColorBuffer texture.
   if (m_antiAliasingMode != None)
-    commit();
+    resolveMultisampleFramebufferInternal();
 
   if (m_softwareRendering && !forceGpuResult) {
     return finishPrepareTextureMailboxSoftware(outMailbox, outReleaseCallback);
   } else {
     return finishPrepareTextureMailboxGpu(outMailbox, outReleaseCallback);
   }
 }
 
 bool DrawingBuffer::finishPrepareTextureMailboxSoftware(
     cc::TextureMailbox* outMailbox,
@@ skipping 24 matching lines @@
                         WTF::passed(std::move(bitmap)), m_size);
   *outReleaseCallback =
       cc::SingleReleaseCallback::Create(convertToBaseCallback(std::move(func)));
   return true;
 }
 
 bool DrawingBuffer::finishPrepareTextureMailboxGpu(
     cc::TextureMailbox* outMailbox,
     std::unique_ptr<cc::SingleReleaseCallback>* outReleaseCallback) {
   if (m_webGLVersion > WebGL1) {
+    m_stateRestorer->setPixelUnpackBufferBindingDirty();
     m_gl->BindBuffer(GL_PIXEL_UNPACK_BUFFER, 0);
   }
 
-  // We must restore the texture binding since creating new textures,
-  // consuming and producing mailboxes changes it.
-  ScopedTextureUnit0BindingRestorer restorer(m_gl, m_activeTextureUnit,
-                                             m_texture2DBinding);
-
   // Specify the buffer that we will put in the mailbox.
   RefPtr<ColorBuffer> colorBufferForMailbox;
   if (m_preserveDrawingBuffer == Discard) {
     // If we can discard the backbuffer, send the old backbuffer directly
     // into the mailbox, and allocate (or recycle) a new backbuffer.
     colorBufferForMailbox = m_backColorBuffer;
     m_backColorBuffer = createOrRecycleColorBuffer();
     attachColorBufferToReadFramebuffer();
 
     // Explicitly specify that m_fbo (which is now bound to the just-allocated
     // m_backColorBuffer) is not initialized, to save GPU memory bandwidth for
     // tile-based GPU architectures.
     if (m_discardFramebufferSupported) {
       const GLenum attachments[3] = {GL_COLOR_ATTACHMENT0, GL_DEPTH_ATTACHMENT,
                                      GL_STENCIL_ATTACHMENT};
+      m_stateRestorer->setFramebufferBindingDirty();
       m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
       m_gl->DiscardFramebufferEXT(GL_FRAMEBUFFER, 3, attachments);
     }
   } else {
     // If we can't discard the backbuffer, create (or recycle) a buffer to put
     // in the mailbox, and copy backbuffer's contents there.
     colorBufferForMailbox = createOrRecycleColorBuffer();
     m_gl->CopySubTextureCHROMIUM(
         m_backColorBuffer->textureId, colorBufferForMailbox->textureId, 0, 0, 0,
         0, m_size.width(), m_size.height(), GL_FALSE, GL_FALSE, GL_FALSE);
@@ skipping 27 matching lines @@
     // mailbox is released (and while the release callback is running).
     auto func = WTF::bind(&DrawingBuffer::mailboxReleasedGpu,
                           RefPtr<DrawingBuffer>(this), colorBufferForMailbox);
     *outReleaseCallback = cc::SingleReleaseCallback::Create(
         convertToBaseCallback(std::move(func)));
   }
 
   // Point |m_frontColorBuffer| to the buffer that we are now presenting.
   m_frontColorBuffer = colorBufferForMailbox;
 
-  // Restore any state that we may have dirtied, and update dirty bits.
-  restoreFramebufferBindings();
-  restorePixelUnpackBufferBindings();
   m_contentsChanged = false;
   setBufferClearNeeded(true);
   return true;
 }
 
 void DrawingBuffer::mailboxReleasedGpu(RefPtr<ColorBuffer> colorBuffer,
                                        const gpu::SyncToken& syncToken,
                                        bool lostResource) {
   // If the mailbox has been returned by the compositor then it is no
   // longer being presented, and so is no longer the front buffer.
@@ skipping 28 matching lines @@
     bool lostResource) {
   DCHECK(!syncToken.HasData());  // No sync tokens for software resources.
   if (m_destructionInProgress || lostResource || m_isHidden || size != m_size)
     return;  // Just delete the bitmap.
 
   RecycledBitmap recycled = {std::move(bitmap), m_size};
   m_recycledBitmaps.append(std::move(recycled));
 }
 
 PassRefPtr<StaticBitmapImage> DrawingBuffer::transferToStaticBitmapImage() {
+  ScopedStateRestorer scopedStateRestorer(this);
+
   // This can be null if the context is lost before the first call to
   // grContext().
   GrContext* grContext = m_contextProvider->grContext();
 
   cc::TextureMailbox textureMailbox;
   std::unique_ptr<cc::SingleReleaseCallback> releaseCallback;
   bool success = false;
   if (grContext) {
     bool forceGpuResult = true;
     success = prepareTextureMailboxInternal(&textureMailbox, &releaseCallback,
@@ skipping 133 matching lines @@
                                         GLuint imageId)
     : drawingBuffer(drawingBuffer),
       parameters(parameters),
       size(size),
       textureId(textureId),
       imageId(imageId) {
   drawingBuffer->contextGL()->GenMailboxCHROMIUM(mailbox.name);
 }
 
 DrawingBuffer::ColorBuffer::~ColorBuffer() {
-  gpu::gles2::GLES2Interface* gl = drawingBuffer->contextGL();
+  gpu::gles2::GLES2Interface* gl = drawingBuffer->m_gl;
   if (receiveSyncToken.HasData())
     gl->WaitSyncTokenCHROMIUM(receiveSyncToken.GetConstData());
   if (imageId) {
     gl->BindTexture(parameters.target, textureId);
     gl->ReleaseTexImage2DCHROMIUM(parameters.target, imageId);
     gl->DestroyImageCHROMIUM(imageId);
+    switch (parameters.target) {
+      case GL_TEXTURE_2D:
+        // Restore the texture binding for GL_TEXTURE_2D, since the client will
+        // expect the previous state.
+        if (drawingBuffer->m_client)
+          drawingBuffer->m_client->DrawingBufferClientRestoreTexture2DBinding();
+        break;
+      case GC3D_TEXTURE_RECTANGLE_ARB:
+        // Rectangle textures aren't exposed to WebGL, so don't bother
+        // restoring this state (there is no meaningful way to restore it).
+        break;
+      default:
+        NOTREACHED();
+        break;
+    }
   }
   gl->DeleteTextures(1, &textureId);
 }
 
 bool DrawingBuffer::initialize(const IntSize& size, bool useMultisampling) {
+  ScopedStateRestorer scopedStateRestorer(this);
+
   if (m_gl->GetGraphicsResetStatusKHR() != GL_NO_ERROR) {
     // Need to try to restore the context again later.
     return false;
   }
 
   m_gl->GetIntegerv(GL_MAX_TEXTURE_SIZE, &m_maxTextureSize);
 
   int maxSampleCount = 0;
   m_antiAliasingMode = None;
   if (useMultisampling) {
@@ skipping 11 matching lines @@
   // The Linux ATI bot fails
   // WebglConformance.conformance_textures_misc_tex_image_webgl, so use storage
   // textures only if ScreenSpaceAntialiasing is enabled, because
   // ScreenSpaceAntialiasing is much faster with storage textures.
   m_storageTextureSupported =
       (m_webGLVersion > WebGL1 ||
        m_extensionsUtil->supportsExtension("GL_EXT_texture_storage")) &&
       m_antiAliasingMode == ScreenSpaceAntialiasing;
   m_sampleCount = std::min(4, maxSampleCount);
 
+  m_stateRestorer->setFramebufferBindingDirty();
   m_gl->GenFramebuffers(1, &m_fbo);
   m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
   if (wantExplicitResolve()) {
     m_gl->GenFramebuffers(1, &m_multisampleFBO);
     m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_multisampleFBO);
     m_gl->GenRenderbuffers(1, &m_multisampleRenderbuffer);
   }
-  if (!reset(size))
+  if (!resizeFramebufferInternal(size))
     return false;
 
   if (m_depthStencilBuffer) {
     DCHECK(wantDepthOrStencil());
     m_hasImplicitStencilBuffer = !m_wantStencil;
   }
 
   if (m_gl->GetGraphicsResetStatusKHR() != GL_NO_ERROR) {
     // It's possible that the drawing buffer allocation provokes a context loss,
     // so check again just in case. http://crbug.com/512302
     return false;
   }
 
   return true;
 }
 
 bool DrawingBuffer::copyToPlatformTexture(gpu::gles2::GLES2Interface* gl,
                                           GLuint texture,
                                           GLenum internalFormat,
                                           GLenum destType,
                                           GLint level,
                                           bool premultiplyAlpha,
                                           bool flipY,
                                           SourceDrawingBuffer sourceBuffer) {
+  ScopedStateRestorer scopedStateRestorer(this);
+
   if (m_contentsChanged) {
-    if (m_antiAliasingMode != None) {
-      commit();
-      restoreFramebufferBindings();
-    }
+    if (m_antiAliasingMode != None)
+      resolveMultisampleFramebufferInternal();
     m_gl->Flush();
   }
 
   // Assume that the destination target is GL_TEXTURE_2D.
   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 35 matching lines @@
   const GLuint64 fenceSync = gl->InsertFenceSyncCHROMIUM();
 
   gl->Flush();
   gpu::SyncToken syncToken;
   gl->GenSyncTokenCHROMIUM(fenceSync, syncToken.GetData());
   m_gl->WaitSyncTokenCHROMIUM(syncToken.GetData());
 
   return true;
 }
 
-GLuint DrawingBuffer::framebuffer() const {
-  return m_fbo;
-}
-
 WebLayer* DrawingBuffer::platformLayer() {
   if (!m_layer) {
     m_layer =
         Platform::current()->compositorSupport()->createExternalTextureLayer(
             this);
 
     m_layer->setOpaque(!m_wantAlphaChannel);
     m_layer->setBlendBackgroundColor(m_wantAlphaChannel);
     m_layer->setPremultipliedAlpha(m_premultipliedAlpha);
     m_layer->setNearestNeighbor(m_filterQuality == kNone_SkFilterQuality);
@@ skipping 33 matching lines @@
 
   m_backColorBuffer = nullptr;
   m_frontColorBuffer = nullptr;
   m_multisampleRenderbuffer = 0;
   m_depthStencilBuffer = 0;
   m_multisampleFBO = 0;
   m_fbo = 0;
 
   if (m_layer)
     GraphicsLayer::unregisterContentsLayer(m_layer->layer());
+
+  m_client = nullptr;
 }
 
 bool DrawingBuffer::resizeDefaultFramebuffer(const IntSize& size) {
   // Recreate m_backColorBuffer.
   m_backColorBuffer = createColorBuffer(size);
 
   attachColorBufferToReadFramebuffer();
 
   if (wantExplicitResolve()) {
+    m_stateRestorer->setFramebufferBindingDirty();
+    m_stateRestorer->setRenderbufferBindingDirty();
     m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_multisampleFBO);
     m_gl->BindRenderbuffer(GL_RENDERBUFFER, m_multisampleRenderbuffer);
     m_gl->RenderbufferStorageMultisampleCHROMIUM(
         GL_RENDERBUFFER, m_sampleCount, getMultisampledRenderbufferFormat(),
         size.width(), size.height());
 
     if (m_gl->GetError() == GL_OUT_OF_MEMORY)
       return false;
 
     m_gl->FramebufferRenderbuffer(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
                                   GL_RENDERBUFFER, m_multisampleRenderbuffer);
   }
 
   if (wantDepthOrStencil()) {
+    m_stateRestorer->setFramebufferBindingDirty();
+    m_stateRestorer->setRenderbufferBindingDirty();
     m_gl->BindFramebuffer(GL_FRAMEBUFFER,
                           m_multisampleFBO ? m_multisampleFBO : m_fbo);
     if (!m_depthStencilBuffer)
       m_gl->GenRenderbuffers(1, &m_depthStencilBuffer);
     m_gl->BindRenderbuffer(GL_RENDERBUFFER, m_depthStencilBuffer);
     if (m_antiAliasingMode == MSAAImplicitResolve) {
       m_gl->RenderbufferStorageMultisampleEXT(GL_RENDERBUFFER, m_sampleCount,
                                               GL_DEPTH24_STENCIL8_OES,
                                               size.width(), size.height());
     } else if (m_antiAliasingMode == MSAAExplicitResolve) {
       m_gl->RenderbufferStorageMultisampleCHROMIUM(
           GL_RENDERBUFFER, m_sampleCount, GL_DEPTH24_STENCIL8_OES, size.width(),
           size.height());
     } else {
       m_gl->RenderbufferStorage(GL_RENDERBUFFER, GL_DEPTH24_STENCIL8_OES,
                                 size.width(), size.height());
     }
     // For ES 2.0 contexts DEPTH_STENCIL is not available natively, so we
     // emulate
     // it at the command buffer level for WebGL contexts.
     m_gl->FramebufferRenderbuffer(GL_FRAMEBUFFER, GL_DEPTH_STENCIL_ATTACHMENT,
                                   GL_RENDERBUFFER, m_depthStencilBuffer);
     m_gl->BindRenderbuffer(GL_RENDERBUFFER, 0);
   }
 
   if (wantExplicitResolve()) {
+    m_stateRestorer->setFramebufferBindingDirty();
     m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_multisampleFBO);
     if (m_gl->CheckFramebufferStatus(GL_FRAMEBUFFER) != GL_FRAMEBUFFER_COMPLETE)
       return false;
   }
 
+  m_stateRestorer->setFramebufferBindingDirty();
   m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
   return m_gl->CheckFramebufferStatus(GL_FRAMEBUFFER) ==
          GL_FRAMEBUFFER_COMPLETE;
 }
 
 void DrawingBuffer::clearFramebuffers(GLbitfield clearMask) {
+  ScopedStateRestorer scopedStateRestorer(this);
+  clearFramebuffersInternal(clearMask);
+}
+
+void DrawingBuffer::clearFramebuffersInternal(GLbitfield clearMask) {
+  m_stateRestorer->setFramebufferBindingDirty();
   // We will clear the multisample FBO, but we also need to clear the
   // non-multisampled buffer.
   if (m_multisampleFBO) {
     m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
     m_gl->Clear(GL_COLOR_BUFFER_BIT);
   }
 
   m_gl->BindFramebuffer(GL_FRAMEBUFFER,
                         m_multisampleFBO ? m_multisampleFBO : m_fbo);
   m_gl->Clear(clearMask);
 }
 
 IntSize DrawingBuffer::adjustSize(const IntSize& desiredSize,
                                   const IntSize& curSize,
                                   int maxTextureSize) {
   IntSize adjustedSize = desiredSize;
 
   // Clamp if the desired size is greater than the maximum texture size for the
   // device.
   if (adjustedSize.height() > maxTextureSize)
     adjustedSize.setHeight(maxTextureSize);
 
   if (adjustedSize.width() > maxTextureSize)
     adjustedSize.setWidth(maxTextureSize);
 
   return adjustedSize;
 }
 
-bool DrawingBuffer::reset(const IntSize& newSize) {
+bool DrawingBuffer::resize(const IntSize& newSize) {
+  ScopedStateRestorer scopedStateRestorer(this);
+  return resizeFramebufferInternal(newSize);
+}
+
+bool DrawingBuffer::resizeFramebufferInternal(const IntSize& newSize) {
   CHECK(!newSize.isEmpty());
   IntSize adjustedSize = adjustSize(newSize, m_size, m_maxTextureSize);
   if (adjustedSize.isEmpty())
     return false;
 
   if (adjustedSize != m_size) {
     do {
       if (!resizeDefaultFramebuffer(adjustedSize)) {
         adjustedSize.scale(s_resourceAdjustedRatio);
         continue;
       }
       break;
     } while (!adjustedSize.isEmpty());
 
     m_size = adjustedSize;
     // Free all mailboxes, because they are now of the wrong size. Only the
     // first call in this loop has any effect.
     m_recycledColorBufferQueue.clear();
     m_recycledBitmaps.clear();
 
     if (adjustedSize.isEmpty())
       return false;
   }
 
+  m_stateRestorer->setClearStateDirty();
   m_gl->Disable(GL_SCISSOR_TEST);
   m_gl->ClearColor(0, 0, 0,
                    defaultBufferRequiresAlphaChannelToBePreserved() ? 1 : 0);
   m_gl->ColorMask(true, true, true, true);
 
   GLbitfield clearMask = GL_COLOR_BUFFER_BIT;
   if (!!m_depthStencilBuffer) {
     m_gl->ClearDepthf(1.0f);
     clearMask |= GL_DEPTH_BUFFER_BIT;
     m_gl->DepthMask(true);
   }
   if (!!m_depthStencilBuffer) {
     m_gl->ClearStencil(0);
     clearMask |= GL_STENCIL_BUFFER_BIT;
     m_gl->StencilMaskSeparate(GL_FRONT, 0xFFFFFFFF);
   }
 
-  clearFramebuffers(clearMask);
+  clearFramebuffersInternal(clearMask);
   return true;
 }
 
-void DrawingBuffer::commit() {
+void DrawingBuffer::resolveAndBindForReadAndDraw() {
+  {
+    ScopedStateRestorer scopedStateRestorer(this);
+    resolveMultisampleFramebufferInternal();
+  }
+  m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
+}
+
+void DrawingBuffer::resolveMultisampleFramebufferInternal() {
+  m_stateRestorer->setFramebufferBindingDirty();
   if (wantExplicitResolve() && !m_contentsChangeCommitted) {
+    m_stateRestorer->setClearStateDirty();
     m_gl->BindFramebuffer(GL_READ_FRAMEBUFFER_ANGLE, m_multisampleFBO);
     m_gl->BindFramebuffer(GL_DRAW_FRAMEBUFFER_ANGLE, m_fbo);
-
-    if (m_scissorEnabled)
-      m_gl->Disable(GL_SCISSOR_TEST);
+    m_gl->Disable(GL_SCISSOR_TEST);
 
     int width = m_size.width();
     int height = m_size.height();
     // Use NEAREST, because there is no scale performed during the blit.
     GLuint filter = GL_NEAREST;
 
     m_gl->BlitFramebufferCHROMIUM(0, 0, width, height, 0, 0, width, height,
                                   GL_COLOR_BUFFER_BIT, filter);
 
     // On old AMD GPUs on OS X, glColorMask doesn't work correctly for
     // multisampled renderbuffers and the alpha channel can be overwritten.
     // Clear the alpha channel of |m_fbo|.
     if (defaultBufferRequiresAlphaChannelToBePreserved() &&
         contextProvider()
             ->getCapabilities()
             .disable_multisampling_color_mask_usage) {
       m_gl->ClearColor(0, 0, 0, 1);
       m_gl->ColorMask(false, false, false, true);
-      m_gl->Clear(GL_COLOR_BUFFER_BIT);
-
-      m_gl->ClearColor(m_clearColor[0], m_clearColor[1], m_clearColor[2],
-                       m_clearColor[3]);
-      m_gl->ColorMask(m_colorMask[0], m_colorMask[1], m_colorMask[2],
-                      m_colorMask[3]);
     }
-
-    if (m_scissorEnabled)
-      m_gl->Enable(GL_SCISSOR_TEST);
   }
 
   m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
-  if (m_antiAliasingMode == ScreenSpaceAntialiasing) {
+  if (m_antiAliasingMode == ScreenSpaceAntialiasing)
     m_gl->ApplyScreenSpaceAntialiasingCHROMIUM();
-  }
   m_contentsChangeCommitted = true;
 }
 
-void DrawingBuffer::restorePixelUnpackBufferBindings() {
-  if (m_webGLVersion > WebGL1) {
-    m_gl->BindBuffer(GL_PIXEL_UNPACK_BUFFER, m_pixelUnpackBufferBinding);
-  }
+void DrawingBuffer::restoreFramebufferBindings() {
+  m_client->DrawingBufferClientRestoreFramebufferBinding();
 }
 
-void DrawingBuffer::restoreFramebufferBindings() {
-  if (m_drawFramebufferBinding && m_readFramebufferBinding) {
-    if (m_drawFramebufferBinding == m_readFramebufferBinding) {
-      m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_readFramebufferBinding);
-    } else {
-      m_gl->BindFramebuffer(GL_READ_FRAMEBUFFER, m_readFramebufferBinding);
-      m_gl->BindFramebuffer(GL_DRAW_FRAMEBUFFER, m_drawFramebufferBinding);
-    }
-    return;
-  }
-  if (!m_drawFramebufferBinding && !m_readFramebufferBinding) {
-    bind(GL_FRAMEBUFFER);
-    return;
-  }
-  if (!m_drawFramebufferBinding) {
-    bind(GL_DRAW_FRAMEBUFFER);
-    m_gl->BindFramebuffer(GL_READ_FRAMEBUFFER, m_readFramebufferBinding);
-  } else {
-    bind(GL_READ_FRAMEBUFFER);
-    m_gl->BindFramebuffer(GL_DRAW_FRAMEBUFFER, m_drawFramebufferBinding);
-  }
+void DrawingBuffer::restoreAllState() {
+  m_client->DrawingBufferClientRestoreScissorTest();
+  m_client->DrawingBufferClientRestoreMaskAndClearValues();
+  m_client->DrawingBufferClientRestorePixelPackAlignment();
+  m_client->DrawingBufferClientRestoreTexture2DBinding();
+  m_client->DrawingBufferClientRestoreRenderbufferBinding();
+  m_client->DrawingBufferClientRestoreFramebufferBinding();
+  m_client->DrawingBufferClientRestorePixelUnpackBufferBinding();
 }
 
 bool DrawingBuffer::multisample() const {
   return m_antiAliasingMode != None;
 }
 
 void DrawingBuffer::bind(GLenum target) {
   m_gl->BindFramebuffer(target,
                         wantExplicitResolve() ? m_multisampleFBO : m_fbo);
 }
 
-void DrawingBuffer::setPackAlignment(GLint param) {
-  m_packAlignment = param;
-}
-
 bool DrawingBuffer::paintRenderingResultsToImageData(
     int& width,
     int& height,
     SourceDrawingBuffer sourceBuffer,
     WTF::ArrayBufferContents& contents) {
+  ScopedStateRestorer scopedStateRestorer(this);
+
   ASSERT(!m_premultipliedAlpha);
   width = size().width();
   height = size().height();
 
   CheckedNumeric<int> dataSize = 4;
   dataSize *= width;
   dataSize *= height;
   if (!dataSize.IsValid())
     return false;
 
   WTF::ArrayBufferContents pixels(width * height, 4,
                                   WTF::ArrayBufferContents::NotShared,
                                   WTF::ArrayBufferContents::DontInitialize);
 
   GLuint fbo = 0;
+  m_stateRestorer->setFramebufferBindingDirty();
   if (sourceBuffer == FrontBuffer && m_frontColorBuffer) {
     m_gl->GenFramebuffers(1, &fbo);
     m_gl->BindFramebuffer(GL_FRAMEBUFFER, fbo);
     m_gl->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
                                m_frontColorBuffer->parameters.target,
                                m_frontColorBuffer->textureId, 0);
   } else {
-    m_gl->BindFramebuffer(GL_FRAMEBUFFER, framebuffer());
+    m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
   }
 
   readBackFramebuffer(static_cast<unsigned char*>(pixels.data()), width, height,
                       ReadbackRGBA, WebGLImageConversion::AlphaDoNothing);
   flipVertically(static_cast<uint8_t*>(pixels.data()), width, height);
 
   if (fbo) {
     m_gl->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
                                m_frontColorBuffer->parameters.target, 0, 0);
     m_gl->DeleteFramebuffers(1, &fbo);
   }
 
-  restoreFramebufferBindings();
-
   pixels.transfer(contents);
   return true;
 }
 
 void DrawingBuffer::readBackFramebuffer(unsigned char* pixels,
                                         int width,
                                         int height,
                                         ReadbackOrder readbackOrder,
                                         WebGLImageConversion::AlphaOp op) {
-  if (m_packAlignment > 4)
-    m_gl->PixelStorei(GL_PACK_ALIGNMENT, 1);
+  m_stateRestorer->setPixelPackAlignmentDirty();
+  m_gl->PixelStorei(GL_PACK_ALIGNMENT, 1);
   m_gl->ReadPixels(0, 0, width, height, GL_RGBA, GL_UNSIGNED_BYTE, pixels);
-  if (m_packAlignment > 4)
-    m_gl->PixelStorei(GL_PACK_ALIGNMENT, m_packAlignment);
 
   size_t bufferSize = 4 * width * height;
 
   if (readbackOrder == ReadbackSkia) {
 #if (SK_R32_SHIFT == 16) && !SK_B32_SHIFT
     // Swizzle red and blue channels to match SkBitmap's byte ordering.
     // TODO(kbr): expose GL_BGRA as extension.
     for (size_t i = 0; i < bufferSize; i += 4) {
       std::swap(pixels[i], pixels[i + 2]);
     }
@@ skipping 21 matching lines @@
     uint8_t* rowA = framebuffer + i * rowBytes;
     uint8_t* rowB = framebuffer + (height - i - 1) * rowBytes;
     memcpy(scanline.data(), rowB, rowBytes);
     memcpy(rowB, rowA, rowBytes);
     memcpy(rowA, scanline.data(), rowBytes);
   }
 }
 
 RefPtr<DrawingBuffer::ColorBuffer> DrawingBuffer::createColorBuffer(
     const IntSize& size) {
+  m_stateRestorer->setFramebufferBindingDirty();
+  m_stateRestorer->setTextureBindingDirty();
+
   // Select the Parameters for the texture object. Allocate the backing
   // GpuMemoryBuffer and GLImage, if one is going to be used.
   ColorBufferParameters parameters;
   GLuint imageId = 0;
   if (shouldUseChromiumImage()) {
     parameters = gpuMemoryBufferColorBufferParameters();
     imageId = m_gl->CreateGpuMemoryBufferImageCHROMIUM(
         size.width(), size.height(), parameters.creationInternalColorFormat,
         GC3D_SCANOUT_CHROMIUM);
   } else {
@@ skipping 32 matching lines @@
                        parameters.creationInternalColorFormat, size.width(),
                        size.height(), 0, parameters.colorFormat,
                        GL_UNSIGNED_BYTE, 0);
     }
   }
 
   // Clear the alpha channel if this is RGB emulated.
   if (imageId && !m_wantAlphaChannel &&
       contextProvider()->getCapabilities().chromium_image_rgb_emulation) {
     GLuint fbo = 0;
+
+    m_stateRestorer->setClearStateDirty();
     m_gl->GenFramebuffers(1, &fbo);
     m_gl->BindFramebuffer(GL_FRAMEBUFFER, fbo);
     m_gl->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
                                parameters.target, textureId, 0);
     m_gl->ClearColor(0, 0, 0, 1);
     m_gl->ColorMask(false, false, false, true);
     m_gl->Clear(GL_COLOR_BUFFER_BIT);
     m_gl->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0,
                                parameters.target, 0, 0);
     m_gl->DeleteFramebuffers(1, &fbo);
-    restoreFramebufferBindings();
-    m_gl->ClearColor(m_clearColor[0], m_clearColor[1], m_clearColor[2],
-                     m_clearColor[3]);
-    m_gl->ColorMask(m_colorMask[0], m_colorMask[1], m_colorMask[2],
-                    m_colorMask[3]);
   }
 
   return adoptRef(new ColorBuffer(this, parameters, size, textureId, imageId));
 }
 
 void DrawingBuffer::attachColorBufferToReadFramebuffer() {
+  m_stateRestorer->setFramebufferBindingDirty();
+  m_stateRestorer->setTextureBindingDirty();
+
   m_gl->BindFramebuffer(GL_FRAMEBUFFER, m_fbo);
 
   GLenum target = m_backColorBuffer->parameters.target;
   GLenum id = m_backColorBuffer->textureId;
 
   m_gl->BindTexture(target, id);
 
   if (m_antiAliasingMode == MSAAImplicitResolve)
     m_gl->FramebufferTexture2DMultisampleEXT(
         GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, target, id, 0, m_sampleCount);
   else
     m_gl->FramebufferTexture2D(GL_FRAMEBUFFER, GL_COLOR_ATTACHMENT0, target, id,
                                0);
-
-  restoreTextureBindings();
-  restoreFramebufferBindings();
 }
 
 bool DrawingBuffer::wantExplicitResolve() {
   return m_antiAliasingMode == MSAAExplicitResolve;
 }
 
 bool DrawingBuffer::wantDepthOrStencil() {
   return m_wantDepth || m_wantStencil;
 }
 
 GLenum DrawingBuffer::getMultisampledRenderbufferFormat() {
   DCHECK(wantExplicitResolve());
   if (m_wantAlphaChannel)
     return GL_RGBA8_OES;
   if (shouldUseChromiumImage() &&
       contextProvider()->getCapabilities().chromium_image_rgb_emulation)
     return GL_RGBA8_OES;
   if (contextProvider()
           ->getCapabilities()
           .disable_webgl_rgb_multisampling_usage)
     return GL_RGBA8_OES;
   return GL_RGB8_OES;
 }
 
-void DrawingBuffer::restoreTextureBindings() {
-  // This class potentially modifies the bindings for GL_TEXTURE_2D and
-  // GL_TEXTURE_RECTANGLE. Only GL_TEXTURE_2D needs to be restored since
-  // the public interface for WebGL does not support GL_TEXTURE_RECTANGLE.
-  m_gl->BindTexture(GL_TEXTURE_2D, m_texture2DBinding);
+DrawingBuffer::ScopedStateRestorer::ScopedStateRestorer(
+    DrawingBuffer* drawingBuffer)
+    : m_drawingBuffer(drawingBuffer) {
+  DCHECK(!m_drawingBuffer->m_stateRestorer);
+  m_drawingBuffer->m_stateRestorer = this;
+}
+
+DrawingBuffer::ScopedStateRestorer::~ScopedStateRestorer() {
+  m_drawingBuffer->m_stateRestorer = nullptr;
+  Client* client = m_drawingBuffer->m_client;
+  if (!client)
+    return;
+
+  if (m_clearStateDirty) {
+    client->DrawingBufferClientRestoreScissorTest();
+    client->DrawingBufferClientRestoreMaskAndClearValues();
+  }
+  if (m_pixelPackAlignmentDirty)
+    client->DrawingBufferClientRestorePixelPackAlignment();
+  if (m_textureBindingDirty)
+    client->DrawingBufferClientRestoreTexture2DBinding();
+  if (m_renderbufferBindingDirty)
+    client->DrawingBufferClientRestoreRenderbufferBinding();
+  if (m_framebufferBindingDirty)
+    client->DrawingBufferClientRestoreFramebufferBinding();
+  if (m_pixelUnpackBufferBindingDirty)
+    client->DrawingBufferClientRestorePixelUnpackBufferBinding();
 }
 
 bool DrawingBuffer::shouldUseChromiumImage() {
   return RuntimeEnabledFeatures::webGLImageChromiumEnabled() &&
          m_chromiumImageUsage == AllowChromiumImage;
 }
 
 }  // namespace blink