Pepper takes ownership of a mailbox before passing it to the texture layer.

gpu/command_buffer/service/gles2_cmd_decoder.cc

 // Copyright (c) 2012 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 "gpu/command_buffer/service/gles2_cmd_decoder.h"
 
 #include <limits.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <stdio.h>
@@ skipping 576 matching lines @@
 
   // Overridden from GLES2Decoder.
   bool Initialize(const scoped_refptr<gfx::GLSurface>& surface,
                   const scoped_refptr<gfx::GLContext>& context,
                   bool offscreen,
                   const gfx::Size& offscreen_size,
                   const DisallowedFeatures& disallowed_features,
                   const std::vector<int32_t>& attribs) override;
   void Destroy(bool have_context) override;
   void SetSurface(const scoped_refptr<gfx::GLSurface>& surface) override;
+  void ReleaseSurface() override;
   void ProduceFrontBuffer(const Mailbox& mailbox) override;
+  void TakeFrontBuffer(const Mailbox& mailbox) override;
+  void ReturnFrontBuffer(const Mailbox& mailbox,
+                         bool is_lost) override;
   bool ResizeOffscreenFrameBuffer(const gfx::Size& size) override;
   void UpdateParentTextureInfo();
   bool MakeCurrent() override;
   GLES2Util* GetGLES2Util() override { return &util_; }
   gfx::GLContext* GetGLContext() override { return context_.get(); }
   ContextGroup* GetContextGroup() override { return group_.get(); }
   Capabilities GetCapabilities() override;
   void RestoreState(const ContextState* prev_state) override;
 
   void RestoreActiveTexture() const override { state_.RestoreActiveTexture(); }
@@ skipping 1411 matching lines @@
 
   // The buffer used to simulate GL_FIXED attribs.
   GLuint fixed_attrib_buffer_id_;
 
   // The size of fiixed attrib buffer.
   GLsizei fixed_attrib_buffer_size_;
 
   // The offscreen frame buffer that the client renders to. With EGL, the
   // depth and stencil buffers are separate. With regular GL there is a single
   // packed depth stencil buffer in offscreen_target_depth_render_buffer_.
   // offscreen_target_stencil_render_buffer_ is unused.

[ccameron, 2016/04/22 18:25:55]

<idle complaining>
GLES2CmdDecoder is far too large a struct, and all of these backbuffer
management things would be good candidates for moving to a separate file.
</idle complaining>

   std::unique_ptr<BackFramebuffer> offscreen_target_frame_buffer_;
   std::unique_ptr<BackTexture> offscreen_target_color_texture_;
   std::unique_ptr<BackRenderbuffer> offscreen_target_color_render_buffer_;
   std::unique_ptr<BackRenderbuffer> offscreen_target_depth_render_buffer_;
   std::unique_ptr<BackRenderbuffer> offscreen_target_stencil_render_buffer_;
   GLenum offscreen_target_color_format_;
   GLenum offscreen_target_depth_format_;
   GLenum offscreen_target_stencil_format_;
   GLsizei offscreen_target_samples_;
   GLboolean offscreen_target_buffer_preserved_;
 
   // The copy that is saved when SwapBuffers is called.
   std::unique_ptr<BackFramebuffer> offscreen_saved_frame_buffer_;
   std::unique_ptr<BackTexture> offscreen_saved_color_texture_;
   scoped_refptr<TextureRef>
       offscreen_saved_color_texture_info_;
 
+  // When a client requests ownership of the swapped front buffer, all
+  // information is saved in this structure, and |in_use| is set to true. When a
+  // client releases ownership, |in_use| is set to false.
+  //
+  // An instance of this struct, with |in_use| = false may be reused instead of
+  // making a new BackTexture.
+  struct SavedBackTexture {
+    std::unique_ptr<BackTexture> back_texture;
+    scoped_refptr<TextureRef> texture_ref;
+    bool in_use;
+  };
+  std::vector<SavedBackTexture> saved_back_textures_;
+
+  // If there's a SavedBackTexture that's not in use, takes that. Otherwise,
+  // generates a new back texture.
+  void CreateBackTexture();
+  size_t create_back_texture_count_for_test_ = 0;
+
+  // Releases all saved BackTextures that are not in use by a client.
+  void ReleaseNotInUseBackTextures();
+
+  // Releases all saved BackTextures.
+  void ReleaseAllBackTextures();
+
+  size_t GetSavedBackTextureCountForTest() override;
+  size_t GetCreatedBackTextureCountForTest() override;
+
   // The copy that is used as the destination for multi-sample resolves.
   std::unique_ptr<BackFramebuffer> offscreen_resolved_frame_buffer_;
   std::unique_ptr<BackTexture> offscreen_resolved_color_texture_;
   GLenum offscreen_saved_color_format_;
 
   std::unique_ptr<QueryManager> query_manager_;
 
   std::unique_ptr<VertexArrayManager> vertex_array_manager_;
 
   std::unique_ptr<ImageManager> image_manager_;
@@ skipping 2082 matching lines @@
   state_.bound_renderbuffer = NULL;
   state_.bound_valuebuffer = NULL;
 
   if (offscreen_saved_color_texture_info_.get()) {
     DCHECK(offscreen_target_color_texture_);
     DCHECK_EQ(offscreen_saved_color_texture_info_->service_id(),
               offscreen_saved_color_texture_->id());
     offscreen_saved_color_texture_->Invalidate();
     offscreen_saved_color_texture_info_ = NULL;
   }
+  ReleaseAllBackTextures();
   if (have_context) {
     if (copy_texture_CHROMIUM_.get()) {
       copy_texture_CHROMIUM_->Destroy();
       copy_texture_CHROMIUM_.reset();
     }
 
     clear_framebuffer_blit_.reset();
 
     if (state_.current_program.get()) {
       program_manager()->UnuseProgram(shader_manager(),
@@ skipping 118 matching lines @@
 }
 
 void GLES2DecoderImpl::SetSurface(
     const scoped_refptr<gfx::GLSurface>& surface) {
   DCHECK(context_->IsCurrent(NULL));
   DCHECK(surface_.get());
   surface_ = surface;
   RestoreCurrentFramebufferBindings();
 }
 
+void GLES2DecoderImpl::ReleaseSurface() {
+  if (!context_.get())
+    return;
+  if (WasContextLost()) {
+    DLOG(ERROR) << "  GLES2DecoderImpl: Trying to release lost context.";
+    return;
+  }
+  context_->ReleaseCurrent(surface_.get());
+  surface_ = nullptr;
+}
+
 void GLES2DecoderImpl::ProduceFrontBuffer(const Mailbox& mailbox) {
+  NOTREACHED();

[ccameron, 2016/04/22 18:25:55]

Should this be "TODO: delete me" as well?

   if (!offscreen_saved_color_texture_.get()) {
     LOG(ERROR) << "Called ProduceFrontBuffer on a non-offscreen context";
     return;
   }
   if (!offscreen_saved_color_texture_info_.get()) {
     GLuint service_id = offscreen_saved_color_texture_->id();
     offscreen_saved_color_texture_info_ = TextureRef::Create(
         texture_manager(), 0, service_id);
     texture_manager()->SetTarget(offscreen_saved_color_texture_info_.get(),
                                  GL_TEXTURE_2D);
     UpdateParentTextureInfo();
   }
   mailbox_manager()->ProduceTexture(
       mailbox, offscreen_saved_color_texture_info_->texture());
 }
 
+void GLES2DecoderImpl::TakeFrontBuffer(const Mailbox& mailbox) {
+  if (!offscreen_saved_color_texture_.get()) {
+    LOG(ERROR) << "Called TakeFrontBuffer on a non-offscreen context";
+    return;
+  }
+
+  if (!offscreen_saved_color_texture_info_.get()) {
+    GLuint service_id = offscreen_saved_color_texture_->id();
+    offscreen_saved_color_texture_info_ = TextureRef::Create(
+        texture_manager(), 0, service_id);
+    texture_manager()->SetTarget(offscreen_saved_color_texture_info_.get(),
+                                 GL_TEXTURE_2D);
+    UpdateParentTextureInfo();
+  }
+
+  mailbox_manager()->ProduceTexture(
+      mailbox, offscreen_saved_color_texture_info_->texture());
+
+  // Save the BackTexture and TextureRef.
+  SavedBackTexture save;
+  save.back_texture.swap(offscreen_saved_color_texture_);
+  save.texture_ref = offscreen_saved_color_texture_info_;
+  offscreen_saved_color_texture_info_ = nullptr;
+  save.in_use = true;
+  saved_back_textures_.push_back(std::move(save));
+
+  CreateBackTexture();
+}
+
+void GLES2DecoderImpl::ReturnFrontBuffer(const Mailbox& mailbox,
+                                         bool is_lost) {
+  for (auto it = saved_back_textures_.begin(); it != saved_back_textures_.end();
+       ++it) {
+    Texture* texture = mailbox_manager()->ConsumeTexture(mailbox);

[ccameron, 2016/04/22 18:25:55]

Pull the ConsumeTexture above the loop?

[erikchen, 2016/04/25 20:58:23]

Done.

+    if (texture != it->texture_ref->texture())
+      continue;
+
+    if (is_lost || it->back_texture->size() != offscreen_size_) {
+      it->back_texture->Invalidate();
+      saved_back_textures_.erase(it);
+      return;
+    }
+
+    it->in_use = false;

[ccameron, 2016/04/22 18:25:55]

Are there circumstances where we would be concerned about the growth of
non-in_use saved_back_textures_?

[erikchen, 2016/04/25 20:58:23]

If this becomes a problem, we can deal with it. I'd like to avoid premature
optimization.

[This is the same thing we do for WebGL].

+    return;
+  }
+
+  NOTREACHED();
+}
+
+void GLES2DecoderImpl::CreateBackTexture() {
+  for (auto it = saved_back_textures_.begin(); it != saved_back_textures_.end();
+       ++it) {
+    if (it->in_use)
+      continue;
+
+    if (it->back_texture->size() != offscreen_size_)
+      continue;
+    offscreen_saved_color_texture_ = std::move(it->back_texture);
+    offscreen_saved_color_texture_info_ = it->texture_ref;
+    saved_back_textures_.erase(it);
+    return;
+  }
+
+  ++create_back_texture_count_for_test_;
+  offscreen_saved_color_texture_.reset(
+      new BackTexture(memory_tracker(), &state_));
+  offscreen_saved_color_texture_->Create();
+  offscreen_saved_color_texture_->AllocateStorage(
+      offscreen_size_, offscreen_saved_color_format_, false);
+  offscreen_saved_frame_buffer_->AttachRenderTexture(
+      offscreen_saved_color_texture_.get());
+}
+
+void GLES2DecoderImpl::ReleaseNotInUseBackTextures() {
+  for (auto& saved_back_texture : saved_back_textures_) {
+    if (!saved_back_texture.in_use)
+      saved_back_texture.back_texture->Invalidate();
+  }
+
+  std::remove_if(saved_back_textures_.begin(), saved_back_textures_.end(),
+                 [](const SavedBackTexture& saved_back_texture) {
+                   return !saved_back_texture.in_use;
+                 });
+}
+
+void GLES2DecoderImpl::ReleaseAllBackTextures() {
+  for (auto& saved_back_texture : saved_back_textures_) {
+    // The texture will be destroyed by texture_ref's destructor.
+    DCHECK(saved_back_texture.texture_ref);
+    saved_back_texture.back_texture->Invalidate();
+  }
+  saved_back_textures_.clear();
+}
+
+size_t GLES2DecoderImpl::GetSavedBackTextureCountForTest() {
+  return saved_back_textures_.size();
+}
+
+size_t GLES2DecoderImpl::GetCreatedBackTextureCountForTest() {
+  return create_back_texture_count_for_test_;
+}
+
 bool GLES2DecoderImpl::ResizeOffscreenFrameBuffer(const gfx::Size& size) {
   bool is_offscreen = !!offscreen_target_frame_buffer_.get();
   if (!is_offscreen) {
     LOG(ERROR) << "GLES2DecoderImpl::ResizeOffscreenFrameBuffer called "
                << " with an onscreen framebuffer.";
     return false;
   }
 
   if (offscreen_size_ == size)
     return true;
@@ skipping 8522 matching lines @@
         "width", offscreen_size_.width(), "height", offscreen_size_.height());
     if (offscreen_size_ != offscreen_saved_color_texture_->size()) {
       // Workaround for NVIDIA driver bug on OS X; crbug.com/89557,
       // crbug.com/94163. TODO(kbr): figure out reproduction so Apple will
       // fix this.
       if (workarounds().needs_offscreen_buffer_workaround) {
         offscreen_saved_frame_buffer_->Create();
         glFinish();
       }
 
+      // The size has changed, so none of the cached BackTextures are useful
+      // anymore.
+      ReleaseNotInUseBackTextures();
+
       // Allocate the offscreen saved color texture.
       DCHECK(offscreen_saved_color_format_);
       offscreen_saved_color_texture_->AllocateStorage(
           offscreen_size_, offscreen_saved_color_format_, false);
 
       offscreen_saved_frame_buffer_->AttachRenderTexture(
           offscreen_saved_color_texture_.get());
       if (offscreen_size_.width() != 0 && offscreen_size_.height() != 0) {
         if (offscreen_saved_frame_buffer_->CheckStatus() !=
             GL_FRAMEBUFFER_COMPLETE) {
@@ skipping 3696 matching lines @@
 }
 
 // Include the auto-generated part of this file. We split this because it means
 // we can easily edit the non-auto generated parts right here in this file
 // instead of having to edit some template or the code generator.
 #include "base/macros.h"
 #include "gpu/command_buffer/service/gles2_cmd_decoder_autogen.h"
 
 }  // namespace gles2
 }  // namespace gpu