More speedup of scrolling when many windowed plugins in a page. Scrolling is...

chrome/browser/render_widget_host.cc

 // Copyright (c) 2006-2008 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 "chrome/browser/render_widget_host.h"
 
 #include "base/gfx/gdi_util.h"
 #include "base/message_loop.h"
 #include "chrome/app/chrome_dll_resource.h"
 #include "chrome/browser/render_widget_helper.h"
@@ skipping 430 matching lines @@
 
   HDWP defer_window_pos_info =
       ::BeginDeferWindowPos(static_cast<int>(plugin_window_moves.size()));
 
   if (!defer_window_pos_info) {
     NOTREACHED();
     return;
   }
 
   for (size_t i = 0; i < plugin_window_moves.size(); ++i) {
-    // Don't invalidate now because that would result in cross process calls
-    // that make scrolling slow.  Instead the window is invalidated
-    // asynchronously by the plugin code.
-    unsigned long flags = SWP_NOREDRAW;
+    unsigned long flags = 0;

[darin (slow to review), 2009/01/22 00:40:03]

maybe add some comments here about the choice of flags?  at least mention why
SWP_NOREDRAW is not specified?

[jam, 2009/01/22 01:03:10]

I was wondering about whether to add a comment or not, but then I thought no
need to comment on flags that aren't used..  Otherwise, why not comment on
SWP_NOCOPYBITS or SWP_NOSENDCHANGING right?

     const WebPluginGeometry& move = plugin_window_moves[i];
 
     if (move.visible)
       flags |= SWP_SHOWWINDOW;
     else
       flags |= SWP_HIDEWINDOW;
 
     HRGN hrgn = ::CreateRectRgn(move.clip_rect.x(),
                                 move.clip_rect.y(),
                                 move.clip_rect.right(),
@@ skipping 378 matching lines @@
       &RenderWidgetHost::CheckRendererIsUnresponsive);
 }
 
 void RenderWidgetHost::RendererExited() {
   BackingStoreManager::RemoveBackingStore(this);
 }
 
 void RenderWidgetHost::SystemThemeChanged() {
   Send(new ViewMsg_ThemeChanged(routing_id_));
 }