MacViews: Don't set window's alpha to 0 if window is already visible.

ui/views/cocoa/bridged_native_widget.mm

 // Copyright 2014 The Chromium Authors. All rights reserved.

[tapted, 2016/10/11 23:05:16]

for the CL description, make sure you follow the guide at
https://www.chromium.org/developers/contributing-code#TOC-Writing-change-list...

That is, you need to say the current behaviour and give rationale for the change
(the bug link helps a lot, but the change description still needs to be
self-contained). You also need to describe the fix.

E.g., you could say

MacViews: <describe change>

Currently repeated calls to Show() a Widget cause a flash. This is because
<reason>. See http://crbug.com/623950#c18

To fix <describe fix>.

BUG=623950

 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #import "ui/views/cocoa/bridged_native_widget.h"
 
 #import <objc/runtime.h>
 #include <stddef.h>
 #include <stdint.h>
 
 #include "base/logging.h"
@@ skipping 533 matching lines @@
   }
   [window_ setContentView:bridged_view_];
 }
 
 void BridgedNativeWidget::SetVisibilityState(WindowVisibilityState new_state) {
   // Ensure that:
   //  - A window with an invisible parent is not made visible.
   //  - A parent changing visibility updates child window visibility.
   //    * But only when changed via this function - ignore changes via the
   //      NSWindow API, or changes propagating out from here.
-  wants_to_be_visible_ = new_state != HIDE_WINDOW;
+  const bool wants_to_be_visible = new_state != HIDE_WINDOW;
+  if (wants_to_be_visible == wants_to_be_visible_)
+    return;
+  wants_to_be_visible_ = wants_to_be_visible;
 
   if (new_state == HIDE_WINDOW) {
     [window_ orderOut:nil];
     DCHECK(!window_visible_);
     return;
   }
 
   DCHECK(wants_to_be_visible_);
   // If the parent (or an ancestor) is hidden, return and wait for it to become
   // visible.
@@ skipping 14 matching lines @@
   // dialog types.
   if (layer() && [window_ isOpaque] &&
       !native_widget_mac_->GetWidget()->IsModal()) {
     initial_visibility_suppressed_ = true;
     [window_ setAlphaValue:0.0];
     [window_ setIgnoresMouseEvents:YES];
   }
 
   if (new_state == SHOW_AND_ACTIVATE_WINDOW) {
     [window_ makeKeyAndOrderFront:nil];
     [NSApp activateIgnoringOtherApps:YES];

[tapted, 2016/10/11 23:05:16]

This line (and the line above) need to happen regardless of the visibility
state. That is, a call to Show() should always raise the window to the top of
the z-order stack, even if it's already visible. I think we just need to modify
the condition on line 584 instead

   } else {
     // ui::SHOW_STATE_INACTIVE is typically used to avoid stealing focus from a
     // parent window. So, if there's a parent, order above that. Otherwise, this
     // will order above all windows at the same level.
     NSInteger parent_window_number = 0;
     if (parent_)
       parent_window_number = [parent_->GetNSWindow() windowNumber];
 
     [window_ orderWindow:NSWindowAbove
               relativeTo:parent_window_number];
@@ skipping 789 matching lines @@
   [bridged_view_ setMouseDownCanMoveWindow:draggable];
   // AppKit will not update its cache of mouseDownCanMoveWindow unless something
   // changes. Previously we tried adding an NSView and removing it, but for some
   // reason it required reposting the mouse-down event, and didn't always work.
   // Calling the below seems to be an effective solution.
   [window_ setMovableByWindowBackground:NO];
   [window_ setMovableByWindowBackground:YES];
 }
 
 }  // namespace views