Plumb ViewportMetrics change notifications around the world and back.

mojo/services/view_manager/public/cpp/lib/view.cc

 // Copyright 2014 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 "view_manager/public/cpp/view.h"
 
 #include <set>
 #include <string>
 
 #include "mojo/public/cpp/application/service_provider_impl.h"
@@ skipping 471 matching lines @@
 void View::LocalSetBounds(const Rect& old_bounds,
                           const Rect& new_bounds) {
   DCHECK(old_bounds.x == bounds_.x);
   DCHECK(old_bounds.y == bounds_.y);
   DCHECK(old_bounds.width == bounds_.width);
   DCHECK(old_bounds.height == bounds_.height);
   ScopedSetBoundsNotifier notifier(this, old_bounds, new_bounds);
   bounds_ = new_bounds;
 }
 
+void View::LocalSetViewportMetrics(const ViewportMetrics& old_metrics,

[sky, 2015/01/27 16:35:08]

Why does this need to take old_metrics? Isn't old_metrics the same as
viewport_metrics_?

[eseidel, 2015/01/27 18:50:04]

I just tried to make it match what LocalSetBounds does. :/  I'm happy to remove
the old_metrics.

+                                   const ViewportMetrics& new_metrics) {
+  DCHECK(viewport_metrics_->size == viewport_metrics_->size);

[sky, 2015/01/27 16:35:08]

I think there is a bug where viewport_metrics_ is null for newly created views.
It can be fixed separately.

[eseidel, 2015/01/27 18:50:04]

Yes, there is.  It's fixed a little in this patch, not completely.  The trouble
when I tried to model after Bounds is that Bounds uses a mojo:Rect which because
it only contains POD types can be allocated as part of View.  Since
ViewportMetrics contains a SizePtr it can't, thus we have bugs like the null bug
you mention.

+  DCHECK(viewport_metrics_->device_pixel_ratio ==
+         viewport_metrics_->device_pixel_ratio);
+  viewport_metrics_ = new_metrics.Clone();
+  FOR_EACH_OBSERVER(
+      ViewObserver, observers_,
+      OnViewViewportMetricsChanged(this, old_metrics, new_metrics));
+}
+
 void View::LocalSetDrawn(bool value) {
   if (drawn_ == value)
     return;
 
   // As IsDrawn() is derived from |visible_| and |drawn_|, only send drawn
   // notification is the value of IsDrawn() is really changing.
   if (IsDrawn() == value) {
     drawn_ = value;
     return;
   }
@@ skipping 44 matching lines @@
 void View::NotifyViewVisibilityChangedUp(View* target) {
   // Start with the parent as we already notified |this|
   // in NotifyViewVisibilityChangedDown.
   for (View* view = parent(); view; view = view->parent()) {
     bool ret = view->NotifyViewVisibilityChangedAtReceiver(target);
     DCHECK(ret);
   }
 }
 
 }  // namespace mojo