Decoupling backbuffer allocation suggestion from frontbuffer allocation suggestion.

content/common/gpu/image_transport_surface_linux.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 "content/common/gpu/image_transport_surface.h"
 
 // This conflicts with the defines in Xlib.h and must come first.
 #include "content/common/gpu/gpu_messages.h"
 
 #include <X11/Xlib.h>
@@ skipping 75 matching lines @@
   // gfx::GLSurface implementation
   virtual bool Initialize() OVERRIDE;
   virtual void Destroy() OVERRIDE;
   virtual bool IsOffscreen() OVERRIDE;
   virtual bool SwapBuffers() OVERRIDE;
   virtual bool PostSubBuffer(int x, int y, int width, int height) OVERRIDE;
   virtual std::string GetExtensions() OVERRIDE;
   virtual gfx::Size GetSize() OVERRIDE;
   virtual bool OnMakeCurrent(gfx::GLContext* context) OVERRIDE;
   virtual unsigned int GetBackingFrameBufferObject() OVERRIDE;
-  virtual void SetBufferAllocation(BufferAllocationState state) OVERRIDE;
+  virtual void SetBackbufferAllocation(bool allocated) OVERRIDE;
+  virtual void SetFrontbufferAllocation(bool allocated) OVERRIDE;
 
  protected:
   // ImageTransportSurface implementation
   virtual void OnNewSurfaceACK(
       uint64 surface_handle, TransportDIB::Handle shm_handle) OVERRIDE;
   virtual void OnBuffersSwappedACK() OVERRIDE;
   virtual void OnPostSubBufferACK() OVERRIDE;
   virtual void OnResizeViewACK() OVERRIDE;
   virtual void OnResize(gfx::Size size) OVERRIDE;
 
  private:
   virtual ~EGLImageTransportSurface() OVERRIDE;
   void ReleaseSurface(scoped_refptr<EGLAcceleratedSurface>* surface);
   void SendBuffersSwapped();
   void SendPostSubBuffer(int x, int y, int width, int height);
 
   // Tracks the current buffer allocation state.
-  BufferAllocationState buffer_allocation_state_;
+  bool backbuffer_suggested_allocation_;
+  bool frontbuffer_suggested_allocation_;
+
+  // The expected size when visible.
+  gfx::Size visible_size_;
 
   uint32 fbo_id_;
 
   scoped_refptr<EGLAcceleratedSurface> back_surface_;
   scoped_refptr<EGLAcceleratedSurface> front_surface_;
   gfx::Rect previous_damage_rect_;
 
   // Whether or not we've successfully made the surface current once.
   bool made_current_;
 
@@ skipping 13 matching lines @@
                            GpuCommandBufferStub* stub);
 
   // gfx::GLSurface implementation:
   virtual bool Initialize() OVERRIDE;
   virtual void Destroy() OVERRIDE;
   virtual bool SwapBuffers() OVERRIDE;
   virtual bool PostSubBuffer(int x, int y, int width, int height) OVERRIDE;
   virtual std::string GetExtensions();
   virtual gfx::Size GetSize() OVERRIDE;
   virtual bool OnMakeCurrent(gfx::GLContext* context) OVERRIDE;
-  virtual void SetBufferAllocation(BufferAllocationState state) OVERRIDE;
+  virtual void SetBackbufferAllocation(bool allocated) OVERRIDE;
+  virtual void SetFrontbufferAllocation(bool allocated) OVERRIDE;
 
  protected:
   // ImageTransportSurface implementation:
   virtual void OnNewSurfaceACK(
       uint64 surface_handle, TransportDIB::Handle shm_handle) OVERRIDE;
   virtual void OnBuffersSwappedACK() OVERRIDE;
   virtual void OnPostSubBufferACK() OVERRIDE;
   virtual void OnResizeViewACK() OVERRIDE;
   virtual void OnResize(gfx::Size size) OVERRIDE;
 
  private:
   virtual ~GLXImageTransportSurface();
 
   // Tell the browser to release the surface.
   void ReleaseSurface();
 
   void SendBuffersSwapped();
   void SendPostSubBuffer(int x, int y, int width, int height);
 
   void ResizeSurface(gfx::Size size);
 
   // Tracks the current buffer allocation state.
-  BufferAllocationState buffer_allocation_state_;
+  bool backbuffer_suggested_allocation_;
+  bool frontbuffer_suggested_allocation_;
 
   XID dummy_parent_;
   gfx::Size size_;
 
   // Whether or not the image has been bound on the browser side.
   bool bound_;
 
   // Whether or not we need to send a resize on the next swap.
   bool needs_resize_;
 
@@ skipping 81 matching lines @@
 EGLAcceleratedSurface::~EGLAcceleratedSurface() {
   glDeleteTextures(1, &texture_);
   eglDestroyImageKHR(gfx::GLSurfaceEGL::GetHardwareDisplay(), image_);
   XFreePixmap(gfx::GLSurfaceEGL::GetNativeDisplay(), pixmap_);
 }
 
 EGLImageTransportSurface::EGLImageTransportSurface(
     GpuChannelManager* manager,
     GpuCommandBufferStub* stub)
     : gfx::PbufferGLSurfaceEGL(false, gfx::Size(16, 16)),
-      buffer_allocation_state_(BUFFER_ALLOCATION_FRONT_AND_BACK),
+      backbuffer_suggested_allocation_(true),
+      frontbuffer_suggested_allocation_(true),
       fbo_id_(0),
       made_current_(false) {
   helper_.reset(new ImageTransportHelper(this,
                                          manager,
                                          stub,
                                          gfx::kNullPluginWindow));
 }
 
 EGLImageTransportSurface::~EGLImageTransportSurface() {
   Destroy();
@@ skipping 45 matching lines @@
   }
 
   made_current_ = true;
   return true;
 }
 
 unsigned int EGLImageTransportSurface::GetBackingFrameBufferObject() {
   return fbo_id_;
 }
 
-void EGLImageTransportSurface::SetBufferAllocation(
-    BufferAllocationState state) {
-  if (buffer_allocation_state_ == state)
+void EGLImageTransportSurface::SetBackbufferAllocation(bool allocated) {
+  if (backbuffer_suggested_allocation_ == allocated)
     return;
-  buffer_allocation_state_ = state;
+  backbuffer_suggested_allocation_ = allocated;
 
-  switch (state) {
-    case BUFFER_ALLOCATION_FRONT_AND_BACK:
-      if (!back_surface_.get() && front_surface_.get())
-        OnResize(front_surface_->size());
-      break;
+  if (backbuffer_suggested_allocation_)
+    OnResize(visible_size_);
+  else
+    ReleaseSurface(&back_surface_);
+}
 
-    case BUFFER_ALLOCATION_FRONT_ONLY:
-      if (back_surface_.get() && front_surface_.get())
-        ReleaseSurface(&back_surface_);
-      break;
-
-    case BUFFER_ALLOCATION_NONE:
-      if (back_surface_.get() && front_surface_.get())
-        ReleaseSurface(&back_surface_);
-      break;
-
-    default:
-      NOTREACHED();
-  }
+void EGLImageTransportSurface::SetFrontbufferAllocation(bool allocated) {
+  if (frontbuffer_suggested_allocation_ == allocated)
+    return;
+  frontbuffer_suggested_allocation_ = allocated;
 }
 
 void EGLImageTransportSurface::ReleaseSurface(
     scoped_refptr<EGLAcceleratedSurface>* surface) {
   if (surface->get()) {
     GpuHostMsg_AcceleratedSurfaceRelease_Params params;
     params.identifier = (*surface)->pixmap();
     helper_->SendAcceleratedSurfaceRelease(params);
     *surface = NULL;
   }
 }
 
 void EGLImageTransportSurface::OnResize(gfx::Size size) {
+  visible_size_ = size;
   back_surface_ = new EGLAcceleratedSurface(size);
 
   GLint previous_fbo_id = 0;
   glGetIntegerv(GL_FRAMEBUFFER_BINDING, &previous_fbo_id);
 
   glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, fbo_id_);
   glFramebufferTexture2DEXT(GL_FRAMEBUFFER,
                             GL_COLOR_ATTACHMENT0,
                             GL_TEXTURE_2D,
                             back_surface_->texture(),
                             0);
   glFlush();
 
   glBindFramebufferEXT(GL_FRAMEBUFFER_EXT, previous_fbo_id);
 
   GpuHostMsg_AcceleratedSurfaceNew_Params params;
   params.width = size.width();
   params.height = size.height();
   params.surface_handle = back_surface_->pixmap();
   helper_->SendAcceleratedSurfaceNew(params);
 
   helper_->SetScheduled(false);
 }
 
 bool EGLImageTransportSurface::SwapBuffers() {
+  DCHECK(backbuffer_suggested_allocation_);
+  if (!frontbuffer_suggested_allocation_)

[jonathan.backer, 2012/05/15 15:53:31]

Need to set |previous_damage_rect_| here. AFAIK, we don't alternate b/w full
swaps and partial swaps (always just one or the other), but I'd like our code to
support that use case.

[mmocny, 2012/05/15 20:02:28]

Actually, I think I need to set previous damage to full frame when the
frontbuffer suggestion changes.  Otherwise, dropping and recreating frontbuffer
without a swap will lead to corruption.
On 2012/05/15 15:53:31, jonathan.backer wrote:

[jonathan.backer, 2012/05/16 02:39:01]

We use |previous_damage_rect_| for two frame damage tracking --- it is the
damage on the current front buffer and we get the damage for the backbuffer
passed in to PostSubBuffer.

The region outside of the |previous_damage_rect_| on the frontbuffer is assumed
to be common to the front and backbuffer. In order to make the backbuffer
complete, we copy over the difference between |preview_damage_rect_| and the
|new_damage_rect| passed in to PostSubBuffer from the front to the backbuffer.

Hope this clarifies the role.

And yes, it is probably sufficient to do this reset when the front buffer is
dropped (although it is somewhat inconsistent with how the code flows... at the
end of SwapBuffers and PostSubBuffer we assume that we have created a new front
buffer and adjusted the previous_damage_rect_ accordingly).

IIRC, |previous_damage_rect_| refers to On 2012/05/15 20:02:28, mmocny wrote:

+    return true;
   front_surface_.swap(back_surface_);
   DCHECK_NE(front_surface_.get(), static_cast<EGLAcceleratedSurface*>(NULL));
   helper_->DeferToFence(base::Bind(
       &EGLImageTransportSurface::SendBuffersSwapped,
       AsWeakPtr()));
 
   gfx::Size expected_size = front_surface_->size();
   if (!back_surface_.get() || back_surface_->size() != expected_size) {
     OnResize(expected_size);
   } else {
     glFramebufferTexture2DEXT(GL_FRAMEBUFFER,
                               GL_COLOR_ATTACHMENT0,
                               GL_TEXTURE_2D,
                               back_surface_->texture(),
                               0);
   }
   previous_damage_rect_ = gfx::Rect(front_surface_->size());
   return true;
 }
 
 void EGLImageTransportSurface::SendBuffersSwapped() {
   GpuHostMsg_AcceleratedSurfaceBuffersSwapped_Params params;
   params.surface_handle = front_surface_->pixmap();
   helper_->SendAcceleratedSurfaceBuffersSwapped(params);
   helper_->SetScheduled(false);
 }
 
 bool EGLImageTransportSurface::PostSubBuffer(
     int x, int y, int width, int height) {
-
+  DCHECK(backbuffer_suggested_allocation_);
+  if (!frontbuffer_suggested_allocation_)

[jonathan.backer, 2012/05/15 15:53:31]

I think that we need to set |previous_damage_rect_| here. Plus we should
probably be asserting that update region is the full backbuffer --- we rely on
being able to read from the frontbuffer for partial updates and we can't in this
case.

[mmocny, 2012/05/15 20:02:28]

I dont think we do read from the frontbuffer (right?), nor should we receive
full frame updates when we dont have one.

We copy from the backbuffer to the frontbuffer all the regions which changed,
for the purpose of ensure that once the front swaps to back it will have the
same contents as the previous backbuffer did.

Since we are not actually swapping buffers when !front, the current backbuffer
will always have the right contents.

The only time we need a full frame update, is right after we re-create the
backbuffer.  To test that, we would probably need a
"backbuffer_was_just_recreated_" flag and then test for that case here.  Is that
worth adding?

On 2012/05/15 15:53:31, jonathan.backer wrote:

[jonathan.backer, 2012/05/16 02:39:01]

We often do a copy from the front buffer to the back buffer in this function
(see comment above). However, we wouldn't if the damage passed in to this
function covered the whole buffer (which is why I suggested that we DCHECK this
if we exit early due to lack of frontbuffer to read from).
The copy goes the other way: glCopyTexSubImage reads from the current FBO  (with
front buffer as colour attachment) to the currently bound texture (the
backbuffer). We make the backbuffer correct by copying the necessary pieces from
the front just before the swap.

[mmocny, 2012/05/16 14:41:50]

I see, thank you for clearing up the direction of the copy, I had thought of it
going the other direction.  I guess we do it this way because we save a region
copy when the same region is dirty each frame?


This actually has me a little worried about the state of the buffer when
rendering frames in the background (for example, for thumbnailer).  The renderer
is not guaranteed to push a full frame when we do not have a frontbuffer (it
actually has no idea about what state frontbuffer is in).

I put the DCHECK in and ran a bunch of tests and this was not an issue, since we
push a full frame after dropping backbuffer, and we only paint a single frame
for thumbnailer which ends up the whole frame.  So, at the moment, we
coincidentally always push a full frame when drawing without a frontbuffer.

However, I left the DCHECK out of this patch since it is not currently
guaranteed, and I will instead file a separate bug to figure this out.

Also, I think that as long as the buffer contents outside the PostSubBuff region
aren't clobbered, things should work fine without the copy from front in this
eary exit step.

+    return true;
   DCHECK_NE(back_surface_.get(), static_cast<EGLAcceleratedSurface*>(NULL));
   gfx::Size expected_size = back_surface_->size();
   bool surfaces_same_size = front_surface_.get() &&
       front_surface_->size() == expected_size;
 
   const gfx::Rect new_damage_rect(x, y, width, height);
 
   // An empty damage rect is a successful no-op.
   if (new_damage_rect.IsEmpty())
     return true;
@@ skipping 78 matching lines @@
 }
 
 void EGLImageTransportSurface::OnResizeViewACK() {
   NOTREACHED();
 }
 
 GLXImageTransportSurface::GLXImageTransportSurface(
     GpuChannelManager* manager,
     GpuCommandBufferStub* stub)
     : gfx::NativeViewGLSurfaceGLX(),
-      buffer_allocation_state_(BUFFER_ALLOCATION_FRONT_AND_BACK),
+      backbuffer_suggested_allocation_(true),
+      frontbuffer_suggested_allocation_(true),
       dummy_parent_(0),
       size_(1, 1),
       bound_(false),
       needs_resize_(false),
       made_current_(false) {
   helper_.reset(new ImageTransportHelper(this,
                                          manager,
                                          stub,
                                          gfx::kNullPluginWindow));
 }
@@ skipping 63 matching lines @@
 }
 
 void GLXImageTransportSurface::ReleaseSurface() {
   DCHECK(bound_);
   GpuHostMsg_AcceleratedSurfaceRelease_Params params;
   params.identifier = window_;
   helper_->SendAcceleratedSurfaceRelease(params);
   bound_ = false;
 }
 
-void GLXImageTransportSurface::SetBufferAllocation(
-    BufferAllocationState state) {
-  if (buffer_allocation_state_ == state)
+void GLXImageTransportSurface::SetBackbufferAllocation(bool allocated) {
+  if (backbuffer_suggested_allocation_ == allocated)
     return;
-  buffer_allocation_state_ = state;
+  backbuffer_suggested_allocation_ = allocated;
 
-  switch (state) {
-    case BUFFER_ALLOCATION_FRONT_AND_BACK: {
-      ResizeSurface(size_);
-      break;
-    }
-    case BUFFER_ALLOCATION_FRONT_ONLY: {
-      ResizeSurface(gfx::Size(1,1));
-      break;
-    }
-    case BUFFER_ALLOCATION_NONE: {
-      ResizeSurface(gfx::Size(1,1));
-      if (bound_)
-        ReleaseSurface();
-      break;
-    }
-    default:
-      NOTREACHED();
-  }
+  if (backbuffer_suggested_allocation_)
+    ResizeSurface(size_);
+  else
+    ResizeSurface(gfx::Size(1,1));
+}
+
+void GLXImageTransportSurface::SetFrontbufferAllocation(bool allocated) {
+  if (frontbuffer_suggested_allocation_ == allocated)
+    return;
+  frontbuffer_suggested_allocation_ = allocated;
+
+  // We recreate frontbuffer by recreating backbuffer and swapping.
+  // But we release frontbuffer by telling UI to release its handle on it.
+  if (!frontbuffer_suggested_allocation_ && bound_)
+    ReleaseSurface();
 }
 
 void GLXImageTransportSurface::ResizeSurface(gfx::Size size) {
   Display* dpy = static_cast<Display*>(GetDisplay());
   XResizeWindow(dpy, window_, size.width(), size.height());
   glXWaitX();
   // Seems necessary to perform a swap after a resize
   // in order to resize the front and back buffers (Intel driver bug).
   // This doesn't always happen with scissoring enabled, so do it now.
   if (gfx::g_GLX_MESA_copy_sub_buffer && gfx::GLSurface::GetCurrent() == this)
     gfx::NativeViewGLSurfaceGLX::SwapBuffers();
   needs_resize_ = true;
 }
 
 void GLXImageTransportSurface::OnResize(gfx::Size size) {
   TRACE_EVENT0("gpu", "GLXImageTransportSurface::OnResize");
   size_ = size;
   ResizeSurface(size_);
 }
 
 bool GLXImageTransportSurface::SwapBuffers() {
+  DCHECK(backbuffer_suggested_allocation_);
+  if (!frontbuffer_suggested_allocation_)
+    return true;
   gfx::NativeViewGLSurfaceGLX::SwapBuffers();
   helper_->DeferToFence(base::Bind(
       &GLXImageTransportSurface::SendBuffersSwapped,
       AsWeakPtr()));
 
   if (needs_resize_) {
     GpuHostMsg_AcceleratedSurfaceNew_Params params;
     params.width = size_.width();
     params.height = size_.height();
     params.surface_handle = window_;
     helper_->SendAcceleratedSurfaceNew(params);
     bound_ = true;
     needs_resize_ = false;
   }
   return true;
 }
 
 void GLXImageTransportSurface::SendBuffersSwapped() {
   GpuHostMsg_AcceleratedSurfaceBuffersSwapped_Params params;
   params.surface_handle = window_;
   helper_->SendAcceleratedSurfaceBuffersSwapped(params);
   helper_->SetScheduled(false);
 }
 
 bool GLXImageTransportSurface::PostSubBuffer(
     int x, int y, int width, int height) {
+  DCHECK(backbuffer_suggested_allocation_);
+  if (!frontbuffer_suggested_allocation_)
+    return true;
   gfx::NativeViewGLSurfaceGLX::PostSubBuffer(x, y, width, height);
   helper_->DeferToFence(base::Bind(
       &GLXImageTransportSurface::SendPostSubBuffer,
       AsWeakPtr(), x, y, width, height));
 
   if (needs_resize_) {
     GpuHostMsg_AcceleratedSurfaceNew_Params params;
     params.width = size_.width();
     params.height = size_.height();
     params.surface_handle = window_;
@@ skipping 244 matching lines @@
                                                    stub,
                                                    surface.get(),
                                                    handle.transport);
   }
 
   if (surface->Initialize())
     return surface;
   else
     return NULL;
 }