MacViews: Reattach children of native windows when they are exposed.

ui/views/cocoa/widget_owner_nswindow_adapter.mm

 // Copyright 2015 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/views/cocoa/widget_owner_nswindow_adapter.h"
 
 #import <Cocoa/Cocoa.h>
 
 #include "base/logging.h"
 #include "base/mac/sdk_forward_declarations.h"
 #include "ui/gfx/geometry/rect.h"
 #include "ui/gfx/geometry/vector2d.h"
 #import "ui/gfx/mac/coordinate_conversion.h"
 #import "ui/views/cocoa/bridged_native_widget.h"
 
 // Bridges an AppKit observer to observe when the (non-views) NSWindow owning a
-// views::Widget will close.
+// views::Widget will close or change occlusion state.
 @interface WidgetOwnerNSWindowAdapterBridge : NSObject {
  @private
   views::WidgetOwnerNSWindowAdapter* adapter_;  // Weak. Owns us.
 }
 - (instancetype)initWithAdapter:(views::WidgetOwnerNSWindowAdapter*)adapter;
 - (void)windowWillClose:(NSNotification*)notification;
+- (void)windowDidChangeOcclusionState:(NSNotification*)notification;
 @end
 
 @implementation WidgetOwnerNSWindowAdapterBridge
 
 - (instancetype)initWithAdapter:(views::WidgetOwnerNSWindowAdapter*)adapter {
   if ((self = [super init]))
     adapter_ = adapter;
   return self;
 }
 
 - (void)windowWillClose:(NSNotification*)notification {
   adapter_->OnWindowWillClose();
 }
 
+- (void)windowDidChangeOcclusionState:(NSNotification*)notification {
+  adapter_->OnWindowDidChangeOcclusionState();
+}
+
 @end
 
 namespace views {
 
 WidgetOwnerNSWindowAdapter::WidgetOwnerNSWindowAdapter(
     BridgedNativeWidget* child,
     NSView* anchor_view)
     : child_(child),
       anchor_view_([anchor_view retain]),
       observer_bridge_(
           [[WidgetOwnerNSWindowAdapterBridge alloc] initWithAdapter:this]) {
 
   // Although the |anchor_view| must be in an NSWindow when the child dialog is
   // created, it's permitted for the |anchor_view| to be removed from its view
   // hierarchy before the child dialog window is fully removed from screen. When
   // this happens, [anchor_view_ window] will become nil, so retain both.
   anchor_window_.reset([[anchor_view_ window] retain]);
   DCHECK(anchor_window_);
 
   [[NSNotificationCenter defaultCenter]
       addObserver:observer_bridge_
          selector:@selector(windowWillClose:)
              name:NSWindowWillCloseNotification
            object:anchor_window_];
+
+  // BridgedNativeWidget removes NSWindow parent/child relationships for hidden
+  // windows. Observe when the parent's visibility changes so they can be
+  // reconnected.
+  [[NSNotificationCenter defaultCenter]
+      addObserver:observer_bridge_
+         selector:@selector(windowDidChangeOcclusionState:)
+             name:NSWindowDidChangeOcclusionStateNotification
+           object:anchor_window_];
 }
 
 void WidgetOwnerNSWindowAdapter::OnWindowWillClose() {
   // Retain the child window before closing it. If the last reference to the
   // NSWindow goes away inside -[NSWindow close], then bad stuff can happen.
   // See e.g. http://crbug.com/616701.
   base::scoped_nsobject<NSWindow> child_window(child_->ns_window(),
                                                base::scoped_policy::RETAIN);
 
   // AppKit child window relationships break when the windows are not visible,
   // so if the child is not visible, it won't currently be a child.
   DCHECK(![child_window isVisible] || [child_window parentWindow]);
   DCHECK([child_window delegate]);
 
   [child_window close];
   // Note: |this| will be deleted here.
 
   DCHECK(![child_window parentWindow]);
   DCHECK(![child_window delegate]);
 }
 
+void WidgetOwnerNSWindowAdapter::OnWindowDidChangeOcclusionState() {
+  // The adapter only needs to handle a parent "show", since the only way it
+  // should be hidden is via -[NSApp hide], and all BridgedNativeWidgets
+  // subscribe to NSApplicationDidHideNotification already.
+  if (![anchor_window_ isVisible])
+    return;
+
+  if (child_->window_visible()) {
+    DCHECK([child_->ns_window() parentWindow]);
+    DCHECK(child_->wants_to_be_visible());
+    return;
+  }
+
+  // The parent relationship should have been removed when the child was hidden.
+  DCHECK(![child_->ns_window() parentWindow]);
+  if (!child_->wants_to_be_visible())
+    return;
+
+  [child_->ns_window() orderWindow:NSWindowAbove
+                        relativeTo:[anchor_window_ windowNumber]];
+
+  // Ordering the window should add back the relationship.
+  DCHECK([child_->ns_window() parentWindow]);
+  DCHECK(child_->window_visible());
+}
+
 NSWindow* WidgetOwnerNSWindowAdapter::GetNSWindow() {
   return anchor_window_;
 }
 
 gfx::Vector2d WidgetOwnerNSWindowAdapter::GetChildWindowOffset() const {
   NSRect rect_in_window =
       [anchor_view_ convertRect:[anchor_view_ bounds] toView:nil];
   NSRect rect_in_screen = [anchor_window_ convertRectToScreen:rect_in_window];
   // Ensure we anchor off the top-left of |anchor_view_| (rect_in_screen.origin
   // is the bottom-left of the view).
@@ skipping 10 matching lines @@
   DCHECK_EQ(child, child_);
   [GetNSWindow() removeChildWindow:child->ns_window()];
   delete this;
 }
 
 WidgetOwnerNSWindowAdapter::~WidgetOwnerNSWindowAdapter() {
   [[NSNotificationCenter defaultCenter] removeObserver:observer_bridge_];
 }
 
 }  // namespace views