Mac HiDPI: Fix scale factor on external display

content/browser/renderer_host/render_widget_host_view_mac.mm

 // 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_mac.h"
 
 #include <QuartzCore/QuartzCore.h>
 
 #include "base/bind.h"
 #include "base/bind_helpers.h"
@@ skipping 350 matching lines @@
 }
 
 RenderWidgetHost* RenderWidgetHostViewMac::GetRenderWidgetHost() const {
   return render_widget_host_;
 }
 
 void RenderWidgetHostViewMac::WasShown() {
   if (!is_hidden_)
     return;
 
-  // Check if the backing scale factor changed while the tab was in the
-  // background.
-  [cocoa_view_ updateTabBackingStoreScaleFactor];
-
   if (web_contents_switch_paint_time_.is_null())
     web_contents_switch_paint_time_ = base::TimeTicks::Now();
   is_hidden_ = false;
   render_widget_host_->WasShown();
 
   // We're messing with the window, so do this to ensure no flashes.
   [[cocoa_view_ window] disableScreenUpdatesUntilFlush];
 }
 
 void RenderWidgetHostViewMac::WasHidden() {
@@ skipping 1044 matching lines @@
 
 - (id)initWithRenderWidgetHostViewMac:(RenderWidgetHostViewMac*)r {
   self = [super initWithFrame:NSZeroRect];
   if (self) {
     editCommand_helper_.reset(new RenderWidgetHostViewMacEditCommandHelper);
     editCommand_helper_->AddEditingSelectorsToClass([self class]);
 
     renderWidgetHostView_.reset(r);
     canBeKeyView_ = YES;
     focusedPluginIdentifier_ = -1;
+    deviceScaleFactor_ = ScaleFactor(self);
 
     // OpenGL support:
     if ([self respondsToSelector:
         @selector(setWantsBestResolutionOpenGLSurface:)]) {
       [self setWantsBestResolutionOpenGLSurface:YES];
     }
     handlingGlobalFrameDidChange_ = NO;
     [[NSNotificationCenter defaultCenter]
         addObserver:self
            selector:@selector(globalFrameDidChange:)
@@ skipping 573 matching lines @@
                name:NSWindowDidChangeScreenNotification
              object:newWindow];
   }
 }
 
 - (void)updateTabBackingStoreScaleFactor {
   if (!renderWidgetHostView_->render_widget_host_)
     return;
 
   float scaleFactor = ScaleFactor(self);
+  if (scaleFactor == deviceScaleFactor_)
+    return;
+  deviceScaleFactor_ = scaleFactor;
+
   BackingStoreMac* backingStore = static_cast<BackingStoreMac*>(
       renderWidgetHostView_->render_widget_host_->GetBackingStore(false));
   if (backingStore)  // NULL in hardware path.
     backingStore->ScaleFactorChanged(scaleFactor);
 
   renderWidgetHostView_->render_widget_host_->SetDeviceScaleFactor(
       scaleFactor);
 }
 
 // http://developer.apple.com/library/mac/#documentation/GraphicsAnimation/Conceptual/HighResolutionOSX/CapturingScreenContents/CapturingScreenContents.html#//apple_ref/doc/uid/TP40012302-CH10-SW4
@@ skipping 943 matching lines @@
     // Pointer comparison only, since we don't know if lastWindow_ is still
     // valid.
     if (newWindow) {
       // If we move into a new window, refresh the frame information. We
       // don't need to do it if it was the same window as it used to be in,
       // since that case is covered by WasShown(). We only want to do this for
       // real browser views, not popups.
       if (newWindow != lastWindow_) {
         lastWindow_ = newWindow;
         renderWidgetHostView_->WindowFrameChanged();
+        [self updateTabBackingStoreScaleFactor];

[Nico, 2012/08/08 00:35:17]

why only for key views?

[sail, 2012/08/08 00:45:00]

Oops. Fixed.

       }
       renderWidgetHostView_->ForceTextureReload();
     }
   }
 
   // If we switch windows (or are removed from the view hierarchy), cancel any
   // open mouse-downs.
   if (hasOpenMouseDown_) {
     WebMouseEvent event;
     event.type = WebInputEvent::MouseUp;
@@ skipping 197 matching lines @@
   if (!string) return NO;
 
   // If the user is currently using an IME, confirm the IME input,
   // and then insert the text from the service, the same as TextEdit and Safari.
   [self confirmComposition];
   [self insertText:string];
   return YES;
 }
 
 @end