Mac: Convince the WindowServer to update the print preview shadow on retina screens

ui/base/cocoa/constrained_window/constrained_window_animation.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.
 
 #import "ui/base/cocoa/constrained_window/constrained_window_animation.h"
 
 #include <stdint.h>
 
 #include "base/files/file_path.h"
 #include "base/location.h"
@@ skipping 205 matching lines @@
   [self setWindowStateForEnd];
   if ([[self delegate] respondsToSelector:@selector(animationDidEnd:)])
     [[self delegate] animationDidEnd:self];
 }
 
 - (void)setCurrentProgress:(NSAnimationProgress)progress {
   [super setCurrentProgress:progress];
 
   if (progress >= 1.0) {
     [self setWindowStateForEnd];
+
+    // Starting in 10.10, the WindowServer forgets to draw the shadow on windows
+    // that animate in this way on retina screens. -[NSWindow invalidateShadow]
+    // doesn't fix it. Neither does toggling -setHasShadow:. But forcing an
+    // update to the window size, and then undoing it, seems to fix the problem.
+    // See http://crbug.com/436884.
+    // TODO(tapted): Find a better fix (this is horrible).
+    NSRect frame = [window_ frame];
+    [window_ setFrame:NSInsetRect(frame, 1, 1) display:NO animate:NO];
+    [window_ setFrame:frame display:NO animate:NO];

[erikchen, 2016/05/09 05:29:06]

uh. okay. I guess. In general I prefer moving away from private APIs, especially
when they cause problems.

[tapted, 2016/05/09 05:35:56]

I hear ya :). I think to resolve this we'd need to either drastically change or
remove the animations, and/or draw the shadow ourselves (maybe by extending the
size of the window slightly and giving the WebContents a parent layer).

Even using the "supported" animations from -[NSWindow animationBehaviour] might
not cope with the layer stuff.

     return;
   }
   [self setWindowStateForValue:[self currentValue]];
 }
 
 - (void)setWindowStateForStart {
   // Subclasses can optionally override this method.
 }
 
 - (void)setWindowStateForValue:(float)value {
@@ skipping 57 matching lines @@
   }
 
   SetWindowScale(window_, scale);
 }
 
 - (void)setWindowStateForEnd {
   SetWindowScale(window_, 1.0);
 }
 
 @end