Avoid calling RWHVWin::GetBackingStore when accelerated compositing is enabled.

content/browser/renderer_host/render_widget_host_view_win.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/browser/renderer_host/render_widget_host_view_win.h"
 
 #include <algorithm>
 #include <map>
 #include <peninputpanel_i.c>
 #include <stack>
@@ skipping 1288 matching lines @@
   }
 
   CleanupCompositorWindow();
 
   ResetTooltip();
   TrackMouseLeave(false);
 }
 
 void RenderWidgetHostViewWin::OnPaint(HDC unused_dc) {
   TRACE_EVENT0("browser", "RenderWidgetHostViewWin::OnPaint");
   if (!render_widget_host_)

[apatrick_chromium, 2012/09/20 22:14:17]

This is is a bit suspicious and I can fix it if you agree. I think OnPaint must
call BeginPaint and EndPaint or bad things happen. This should be immediately
below thee definition of paint_dc.

[sky, 2012/09/20 22:39:52]

Agreed.

[apatrick_chromium, 2012/09/20 22:52:31]

Done.

     return;
 
   DCHECK(render_widget_host_->GetProcess()->HasConnection());
 
+  // Grab the region to paint before creation of paint_dc since it clears the
+  // damage region.
+  base::win::ScopedGDIObject<HRGN> damage_region(CreateRectRgn(0, 0, 0, 0));

[apatrick_chromium, 2012/09/20 22:14:17]

This has to be above the definition of paint_dc as the comment says.

+  GetUpdateRgn(damage_region, FALSE);
+
+  CPaintDC paint_dc(m_hWnd);

[apatrick_chromium, 2012/09/20 22:14:17]

This moved up so everything uses a single definition of paint_dc.

+
   // If the GPU process is rendering to a child window, compositing is
   // already triggered by damage to compositor_host_window_, so all we need to
   // do here is clear borders during resize.
   if (compositor_host_window_ &&
       render_widget_host_->is_accelerated_compositing_active()) {
-    // We initialize paint_dc here so that BeginPaint()/EndPaint()
-    // get called to validate the region.
-    CPaintDC paint_dc(m_hWnd);
     RECT host_rect, child_rect;
     GetClientRect(&host_rect);
     if (::GetClientRect(compositor_host_window_, &child_rect) &&
         (child_rect.right < host_rect.right ||
          child_rect.bottom < host_rect.bottom)) {
       paint_dc.FillRect(&host_rect,
           reinterpret_cast<HBRUSH>(GetStockObject(WHITE_BRUSH)));
     }
     return;
   }
 
+  if (accelerated_surface_.get() &&

[apatrick_chromium, 2012/09/20 22:14:17]

And this moved above the call to GetBackingStore.

+      render_widget_host_->is_accelerated_compositing_active()) {
+    AcceleratedPaint(paint_dc.m_hDC);
+    return;
+  }
+
   about_to_validate_and_paint_ = true;
   BackingStoreWin* backing_store = static_cast<BackingStoreWin*>(
       render_widget_host_->GetBackingStore(true));
 
   // We initialize |paint_dc| (and thus call BeginPaint()) after calling
   // GetBackingStore(), so that if it updates the invalid rect we'll catch the
   // changes and repaint them.
   about_to_validate_and_paint_ = false;
 
-  // Grab the region to paint before creation of paint_dc since it clears the
-  // damage region.
-  base::win::ScopedGDIObject<HRGN> damage_region(CreateRectRgn(0, 0, 0, 0));
-  GetUpdateRgn(damage_region, FALSE);
-
   if (compositor_host_window_ && hide_compositor_window_at_next_paint_) {
     ::ShowWindow(compositor_host_window_, SW_HIDE);
     hide_compositor_window_at_next_paint_ = false;
   }
 
-  CPaintDC paint_dc(m_hWnd);
-
   gfx::Rect damaged_rect(paint_dc.m_ps.rcPaint);
   if (damaged_rect.IsEmpty())
     return;
 
-  if (accelerated_surface_.get() &&
-      render_widget_host_->is_accelerated_compositing_active()) {
-    AcceleratedPaint(paint_dc.m_hDC);
-    return;
-  }
-
   if (backing_store) {
     gfx::Rect bitmap_rect(gfx::Point(), backing_store->size());
 
     bool manage_colors = BackingStoreWin::ColorManagementEnabled();
     if (manage_colors)
       SetICMMode(paint_dc.m_hDC, ICM_ON);
 
     // Blit only the damaged regions from the backing store.
     DWORD data_size = GetRegionData(damage_region, 0, NULL);
     scoped_array<char> region_data_buf;
@@ skipping 1728 matching lines @@
   // receive a focus change in the context of a pointer down message, it means
   // that the pointer down message occurred on the edit field and we should
   // display the on screen keyboard
   if (!received_focus_change_after_pointer_down_ && virtual_keyboard_)
     DisplayOnScreenKeyboardIfNeeded();
   received_focus_change_after_pointer_down_ = false;
   pointer_down_context_ = false;
 }
 
 }  // namespace content