Fixes issues when switching between software and compositing.

content/renderer/browser_plugin/browser_plugin_compositing_helper.cc

 // Copyright (c) 2013 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 "content/renderer/browser_plugin/browser_plugin_compositing_helper.h"
 
 #include "cc/texture_layer.h"
 #include "content/common/browser_plugin_messages.h"
+#include "content/renderer/browser_plugin/browser_plugin_manager.h"
 #include "content/renderer/render_thread_impl.h"
+#include "third_party/khronos/GLES2/gl2.h"
+#include "third_party/WebKit/Source/Platform/chromium/public/WebGraphicsContext3D.h"
+#include "third_party/WebKit/Source/Platform/chromium/public/WebSharedGraphicsContext3D.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebPluginContainer.h"
 #include "webkit/compositor_bindings/web_layer_impl.h"
 
 namespace content {
 
-static void SendACK(const std::string& mailbox_name,
-                    int host_route_id,
-                    int gpu_route_id,
-                    int gpu_host_id,
-                    unsigned sync_point) {
-  RenderThread::Get()->Send(
-      new BrowserPluginHostMsg_BuffersSwappedACK(
-          host_route_id,
-          gpu_route_id,
-          gpu_host_id,
-          mailbox_name,
-          sync_point));
-}
-
 BrowserPluginCompositingHelper::BrowserPluginCompositingHelper(
     WebKit::WebPluginContainer* container,
+    BrowserPluginManager* manager,
     int host_routing_id)
     : host_routing_id_(host_routing_id),
       last_mailbox_valid_(false),
-      container_(container) {
+      ack_pending_(true),
+      container_(container),
+      browser_plugin_manager_(manager) {
 }
 
 BrowserPluginCompositingHelper::~BrowserPluginCompositingHelper() {
-  container_->setWebLayer(NULL);
 }
 
 void BrowserPluginCompositingHelper::EnableCompositing(bool enable) {
   if (enable && !texture_layer_) {
     texture_layer_ = cc::TextureLayer::createForMailbox();
     web_layer_.reset(new WebKit::WebLayerImpl(texture_layer_));
   }
 
   container_->setWebLayer(enable ? web_layer_.get() : NULL);
 }
 
+// If we have a mailbox that was freed up from the compositor,
+// but we are not expected to return it to the guest renderer
+// via an ACK, we should free it because we now own it.
+// To free the mailbox memory, we need a context to consume it
+// into a texture ID and then delete this texture ID.
+// We use a shared graphics context accessible from the main
+// thread to do it.
+void BrowserPluginCompositingHelper::FreeMailboxMemory(
+    const std::string& mailbox_name,
+    unsigned sync_point) {
+  if (mailbox_name.empty())
+    return;
+
+  WebKit::WebGraphicsContext3D *context =
+     WebKit::WebSharedGraphicsContext3D::mainThreadContext();
+  DCHECK(context);
+  // When a buffer is released from the compositor, we also get a
+  // sync point that specifies when in the command buffer
+  // it's safe to use it again.
+  // If the sync point is non-zero, we need to tell our context
+  // to wait until this sync point is reached before we can safely
+  // delete the buffer.
+  if (sync_point)
+    context->waitSyncPoint(sync_point);
+
+  unsigned texture_id = context->createTexture();
+  context->bindTexture(GL_TEXTURE_2D, texture_id);
+  context->consumeTextureCHROMIUM(
+      GL_TEXTURE_2D,
+      reinterpret_cast<const int8*>(mailbox_name.data()));
+  context->deleteTexture(texture_id);
+}
+
+void BrowserPluginCompositingHelper::MailboxReleased(
+    const std::string& mailbox_name,
+    int gpu_route_id,
+    int gpu_host_id,
+    unsigned sync_point) {
+  // We need to send an ACK to TextureImageTransportSurface
+  // for every buffer it sends us. However, if a buffer is freed up from
+  // the compositor in cases like switching back to SW mode without a new
+  // buffer arriving, no ACK is needed and we destroy this buffer.
+  if (!ack_pending_) {
+    FreeMailboxMemory(mailbox_name, sync_point);
+    last_mailbox_valid_ = false;
+    return;
+  }
+  ack_pending_ = false;
+  browser_plugin_manager_->Send(
+      new BrowserPluginHostMsg_BuffersSwappedACK(
+          host_routing_id_,
+          gpu_route_id,
+          gpu_host_id,
+          mailbox_name,
+          sync_point));
+}
+
+void BrowserPluginCompositingHelper::OnContainerDestroy() {
+  if (container_)
+    container_->setWebLayer(NULL);
+  container_ = NULL;
+
+  texture_layer_ = NULL;
+  web_layer_.reset();
+}
+
 void BrowserPluginCompositingHelper::OnBuffersSwapped(
     const gfx::Size& size,
     const std::string& mailbox_name,
     int gpu_route_id,
     int gpu_host_id) {
+  ack_pending_ = true;
+  // Browser plugin getting destroyed, do a fast ACK.
+  if (!texture_layer_) {
+    MailboxReleased(mailbox_name, gpu_route_id, gpu_host_id, 0);
+    return;
+  }
+
+  // The size of browser plugin container is not always equal to the size
+  // of the buffer that arrives here. This could be for a number of reasons,
+  // including autosize and a resize in process.

[Fady Samuel, 2013/01/18 20:07:47]

..in progress.

+  // During resize, the container size changes first and then some time
+  // later, a new buffer with updated size will arrive. During this process

[Fady Samuel, 2013/01/18 20:07:47]

During this process,

+  // we need to make sure that things are still displayed pixel perfect.
+  // We accoplish this by modifying texture coordinates in the layer,

[Fady Samuel, 2013/01/18 20:07:47]

We accomplish

+  // and either buffer size or container size change triggers the need
+  // to also update texture coordinates.

[Fady Samuel, 2013/01/18 20:07:47]

What does this do visually? This is for gutter right? Could you please explain
that?

   if (buffer_size_ != size) {
     buffer_size_ = size;
     UpdateUVRect();
   }
-  if (!last_mailbox_valid_)
-    SendACK(std::string(), host_routing_id_, gpu_route_id, gpu_host_id, 0);
 
   bool current_mailbox_valid = !mailbox_name.empty();
-  if (!current_mailbox_valid && !last_mailbox_valid_)
-    return;
+  if (!last_mailbox_valid_) {
+    MailboxReleased(std::string(), gpu_route_id, gpu_host_id, 0);
+    if (!current_mailbox_valid)
+      return;
+  }
 
   cc::TextureLayer::MailboxCallback callback;
   if (current_mailbox_valid) {
-    callback = base::Bind(&SendACK,
+    callback = base::Bind(&BrowserPluginCompositingHelper::MailboxReleased,
+                          scoped_refptr<BrowserPluginCompositingHelper>(this),
                           mailbox_name,
-                          host_routing_id_,
                           gpu_route_id,
                           gpu_host_id);
   }
+
   texture_layer_->setTextureMailbox(mailbox_name, callback);
   last_mailbox_valid_ = current_mailbox_valid;
 }
 
 void BrowserPluginCompositingHelper::SetContainerSize(const gfx::Size& size) {
   if (container_size_ == size)
     return;
 
   container_size_ = size;
   UpdateUVRect();
 }
 
 void BrowserPluginCompositingHelper::UpdateUVRect() {
   if (!texture_layer_)
     return;
 
   gfx::RectF uv_rect(0, 0, 1, 1);
   if (!buffer_size_.IsEmpty() && !container_size_.IsEmpty()) {
     uv_rect.set_width(static_cast<float>(container_size_.width()) /
                       static_cast<float>(buffer_size_.width()));
     uv_rect.set_height(static_cast<float>(container_size_.height()) /
                        static_cast<float>(buffer_size_.height()));
   }
   texture_layer_->setUVRect(uv_rect);
 }
 
 }  // namespace content