Update BackingStore to handle the case where our Cocoa view has...

chrome/browser/renderer_host/render_widget_host_view_mac.mm

 // 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/renderer_host/render_widget_host_view_mac.h"
 
 #include "base/histogram.h"
 #include "base/string_util.h"
 #include "base/sys_string_conversions.h"
 #include "chrome/browser/browser_trial.h"
@@ skipping 531 matching lines @@
   DCHECK(renderWidgetHostView_->render_widget_host_->process()->HasConnection());
   DCHECK(!renderWidgetHostView_->about_to_validate_and_paint_);
 
   renderWidgetHostView_->invalid_rect_ = dirtyRect;
   renderWidgetHostView_->about_to_validate_and_paint_ = true;
   BackingStore* backing_store =
       renderWidgetHostView_->render_widget_host_->GetBackingStore(true);
   renderWidgetHostView_->about_to_validate_and_paint_ = false;
   dirtyRect = renderWidgetHostView_->invalid_rect_;
 
-  if (backing_store && backing_store->cg_layer()) {
+  if (backing_store) {
     NSRect view_bounds = [self bounds];
     gfx::Rect damaged_rect([self NSRectToRect:dirtyRect]);
 
     gfx::Rect bitmap_rect(0, 0,
                           backing_store->size().width(),
                           backing_store->size().height());
 
     gfx::Rect paint_rect = bitmap_rect.Intersect(damaged_rect);
     if (!paint_rect.IsEmpty()) {
-      CGContextRef context = static_cast<CGContextRef>(
-          [[NSGraphicsContext currentContext] graphicsPort]);
+      // if we have a CGLayer, draw that into the window
+      if (backing_store->cg_layer()) {
+        CGContextRef context = static_cast<CGContextRef>(
+            [[NSGraphicsContext currentContext] graphicsPort]);
 
-      // TODO: add clipping to dirtyRect if it improves drawing performance.
-      CGContextDrawLayerAtPoint(context, CGPointMake(0.0, 0.0),
-                                backing_store->cg_layer());
+        // TODO: add clipping to dirtyRect if it improves drawing performance.
+        CGContextDrawLayerAtPoint(context, CGPointMake(0.0, 0.0),
+                                  backing_store->cg_layer());
+      } else {
+        // if we haven't created a layer yet, draw the cached bitmap into
+        // the window.  The CGLayer will be created the next time the renderer
+        // paints.
+        CGContextRef context = static_cast<CGContextRef>(
+            [[NSGraphicsContext currentContext] graphicsPort]);
+        scoped_cftyperef<CGImageRef> image(
+            CGBitmapContextCreateImage(backing_store->cg_bitmap()));

[rohitrao (ping after 24h), 2009/08/31 21:18:13]

What will happen if cg_bitmap() returns NULL?  Do we want to add a DCHECK to
make sure either the layer or the bitmap exists?

[Amanda Walker, 2009/08/31 21:22:30]

Since one or the other always gets created in the BackingStore constructor, I
don't see too much need for a check here.  Since CGBitmapContextCreate should
only fail if the process is completely out of RAM, it seems a bit superfluous to
add a check for that case in the constructor, but that would be the place to do
it.

+        CGContextDrawImage(context, bitmap_rect.ToCGRect(), image);
+      }
     }
 
     // Fill the remaining portion of the damaged_rect with white
     if (damaged_rect.right() > bitmap_rect.right()) {
       int x = std::max(bitmap_rect.right(), damaged_rect.x());
       int y = std::min(bitmap_rect.bottom(), damaged_rect.bottom());
       int width = damaged_rect.right() - x;
       int height = damaged_rect.y() - y;
 
       // Extra fun to get around the fact that gfx::Rects can't have
@@ skipping 504 matching lines @@
     renderWidgetHostView_->render_widget_host_->ForwardKeyboardEvent(event);
   } else {
     renderWidgetHostView_->render_widget_host_->ImeConfirmComposition(
         UTF8ToUTF16([im_text UTF8String]));
   }
   renderWidgetHostView_->im_composing_ = false;
 }
 
 @end