Listen to Display reconfiguration and notify DisplayObservers on Mac.

ui/gfx/screen_display_observer_delegate.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 "ui/gfx/screen_display_observer_delegate.h"
+
+#include "ui/gfx/display.h"
+
+ScreenDisplayObserverDelegate::ScreenDisplayObserverDelegate() {
+}
+
+ScreenDisplayObserverDelegate::~ScreenDisplayObserverDelegate() {
+}
+
+void ScreenDisplayObserverDelegate::AddObserver(gfx::DisplayObserver* obs) {
+  observer_list_.AddObserver(obs);
+}
+
+void ScreenDisplayObserverDelegate::RemoveObserver(gfx::DisplayObserver* obs) {
+  observer_list_.RemoveObserver(obs);
+}
+
+void ScreenDisplayObserverDelegate::NotifyDisplaysChanged(
+    const std::vector<gfx::Display>& old_displays,
+    const std::vector<gfx::Display>& new_displays) {
+  typedef std::vector<gfx::Display>::const_iterator DisplayIt;
+  std::vector<gfx::Display>::const_iterator old_it = old_displays.begin();
+  for (; old_it != old_displays.end(); ++old_it) {
+    bool found = false;

[oshima, 2014/07/09 17:12:51]

can you use std::find_if ? I usualyl prefer loop over std::find, but I think
this method will be simpler with std::find.

[mlamouri (slow - plz ping), 2014/07/10 12:54:34]

Unfortunately, std::find() will compare the items with a given value, in that
case, it would check if the displays are equal. I'm checking if there ids are
equal so it wouldn't work that well unless we add an operator== on display using
the id... I'm not sure that would be a great idea.

An alternative would be to use std::find_if but in the current state of C++ in
Chromium, we might not be able to do it in a nicer way that this loop (ie. we
can't use anonymous functions).

Let me know if I misunderstood your comment.

[oshima, 2014/07/10 18:11:58]

Yes, I meant std:find_if (sorry I mentioned find_if, but omitted _if for the
rest of my comment)

https://codereview.chromium.org/382833002/diff/20001/ui/gfx/display_change_no...

This is easier to read IMO.

Can you also add unit test for notifier?

+    for (std::vector<gfx::Display>::const_iterator new_it =
+         new_displays.begin(); new_it != new_displays.end(); ++new_it) {
+      if (old_it->id() == new_it->id()) {
+        found = true;
+        break;
+      }
+    }
+
+    if (!found) {
+      FOR_EACH_OBSERVER(gfx::DisplayObserver, observer_list_,
+                        OnDisplayRemoved(*old_it));
+    }
+  }
+
+  for (std::vector<gfx::Display>::const_iterator new_it =
+          new_displays.begin(); new_it != new_displays.end(); ++new_it) {
+    bool found = false;
+    for (std::vector<gfx::Display>::const_iterator old_it =
+         old_displays.begin(); old_it != old_displays.end(); ++old_it) {
+      if (new_it->id() != old_it->id())
+        continue;
+
+      uint32_t metrics = gfx::DisplayObserver::DISPLAY_METRIC_NONE;
+
+      if (new_it->bounds() != old_it->bounds())
+        metrics |= gfx::DisplayObserver::DISPLAY_METRIC_BOUNDS;
+
+      if (new_it->rotation() != old_it->rotation())
+        metrics |= gfx::DisplayObserver::DISPLAY_METRIC_ROTATION;
+
+      if (new_it->work_area() != old_it->work_area())
+        metrics |= gfx::DisplayObserver::DISPLAY_METRIC_WORK_AREA;
+
+      if (new_it->device_scale_factor() != old_it->device_scale_factor())
+        metrics |= gfx::DisplayObserver::DISPLAY_METRIC_DEVICE_SCALE_FACTOR;
+
+      if (metrics != gfx::DisplayObserver::DISPLAY_METRIC_NONE) {
+        FOR_EACH_OBSERVER(gfx::DisplayObserver,
+                          observer_list_,
+                          OnDisplayMetricsChanged(*new_it, metrics));
+      }
+
+      found = true;
+      break;
+    }
+
+    if (!found) {
+      FOR_EACH_OBSERVER(gfx::DisplayObserver, observer_list_,
+                        OnDisplayAdded(*new_it));
+    }
+  }
+}