aw: Block child compositor if frame is not consumed by parent

android_webview/browser/browser_view_renderer.cc

 // Copyright 2014 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 "android_webview/browser/browser_view_renderer.h"
 
 #include "android_webview/browser/browser_view_renderer_client.h"
 #include "android_webview/browser/shared_renderer_state.h"
 #include "android_webview/common/aw_switches.h"
 #include "android_webview/public/browser/draw_gl.h"
@@ skipping 232 matching lines @@
   if (is_hardware_canvas && attached_to_window_ &&
       !switches::ForceAuxiliaryBitmap()) {
     return OnDrawHardware(java_canvas);
   }
 
   // Perform a software draw
   return OnDrawSoftware(java_canvas);
 }
 
 bool BrowserViewRenderer::OnDrawHardware(jobject java_canvas) {
+  TRACE_EVENT0("android_webview", "BrowserViewRenderer::OnDrawHardware");
   if (!compositor_)
     return false;
 
-  if (last_on_draw_global_visible_rect_.IsEmpty())
+  if (last_on_draw_global_visible_rect_.IsEmpty()) {
+    TRACE_EVENT_INSTANT0("android_webview",
+                         "EarlyOut_EmptyVisibleRect",
+                         TRACE_EVENT_SCOPE_THREAD);
     return client_->RequestDrawGL(java_canvas, false);
+  }
 
   if (!hardware_enabled_) {
     hardware_enabled_ = compositor_->InitializeHwDraw();
     if (hardware_enabled_) {
       tile_manager_key_ = GlobalTileManager::GetInstance()->PushBack(this);
     }
   }
   if (!hardware_enabled_)
     return false;
 
+
   ReturnResourceFromParent();
   SynchronousCompositorMemoryPolicy new_policy = CalculateDesiredMemoryPolicy();
   RequestMemoryPolicy(new_policy);
   compositor_->SetMemoryPolicy(memory_policy_);
 
+  if (shared_renderer_state_->HasDrawGLInput()) {
+    TRACE_EVENT_INSTANT0("android_webview",
+                         "EarlyOut_PreviousFrameUnconsumed",
+                         TRACE_EVENT_SCOPE_THREAD);
+    // TODO(boliu): Rename this method. We didn't actually composite here.
+    DidComposite();
+    return client_->RequestDrawGL(java_canvas, false);
+  }
+
   scoped_ptr<DrawGLInput> draw_gl_input(new DrawGLInput);
   draw_gl_input->scroll_offset = last_on_draw_scroll_offset_;
   draw_gl_input->width = width_;
   draw_gl_input->height = height_;
 
   parent_draw_constraints_ = shared_renderer_state_->ParentDrawConstraints();
   gfx::Size surface_size(width_, height_);
   gfx::Rect viewport(surface_size);
   gfx::Rect clip = viewport;
   gfx::Transform transform_for_tile_priority =
@@ skipping 14 matching lines @@
                                 viewport,
                                 clip,
                                 viewport_rect_for_tile_priority,
                                 transform_for_tile_priority);
   if (!frame.get())
     return false;
 
   GlobalTileManager::GetInstance()->DidUse(tile_manager_key_);
 
   frame->AssignTo(&draw_gl_input->frame);
-  ReturnUnusedResource(shared_renderer_state_->PassDrawGLInput());

[hush (inactive), 2014/09/20 02:15:53]

why is this removed?

[boliu, 2014/09/20 02:20:21]

If we are consuming the input, we can't detect when parent doesn't consume it

   shared_renderer_state_->SetDrawGLInput(draw_gl_input.Pass());
   DidComposite();
   return client_->RequestDrawGL(java_canvas, false);
 }
 
 void BrowserViewRenderer::UpdateParentDrawConstraints() {
   // Post an invalidate if the parent draw constraints are stale and there is
   // no pending invalidate.
   if (!parent_draw_constraints_.Equals(
           shared_renderer_state_->ParentDrawConstraints()))
@@ skipping 485 matching lines @@
     base::StringAppendF(&str,
                         "surface width height: [%d %d] ",
                         draw_info->width,
                         draw_info->height);
     base::StringAppendF(&str, "is_layer: %d ", draw_info->is_layer);
   }
   return str;
 }
 
 }  // namespace android_webview