Have panels respond to changes in work area on Linux.

ui/base/x/root_window_property_watcher_x.cc

Index: ui/base/x/root_window_property_watcher_x.cc
diff --git a/ui/base/x/root_window_property_watcher_x.cc b/ui/base/x/root_window_property_watcher_x.cc
new file mode 100644
index 0000000000000000000000000000000000000000..de8b61eba4ab7c6787a0fff2f8f6a7d050c4beb5
--- /dev/null
+++ b/ui/base/x/root_window_property_watcher_x.cc
@@ -0,0 +1,58 @@
+// Copyright (c) 2011 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/base/x/root_window_property_watcher_x.h"
+
+#include <gdk/gdk.h>
+#include <gdk/gdkx.h>
+
+#include "ui/base/x/active_window_watcher_x.h"
+#include "ui/base/x/work_area_watcher_x.h"
+
+namespace ui {
+
+namespace internal {
+
+// static
+RootWindowPropertyWatcherX* RootWindowPropertyWatcherX::GetInstance() {
+  return Singleton<RootWindowPropertyWatcherX>::get();
+}
+
+RootWindowPropertyWatcherX::RootWindowPropertyWatcherX() {
+  GdkWindow* root = gdk_get_default_root_window();
+
+  // Set up X Event filter to listen for PropertyChange X events.
+  // Don't use XSelectInput directly here, as gdk internally seems to cache the
+  // mask and reapply XSelectInput after this, resetting any mask we set here.
+  gdk_window_set_events(root,
+                        static_cast<GdkEventMask>(gdk_window_get_events(root) |
+                                                  GDK_PROPERTY_CHANGE_MASK));
+  gdk_window_add_filter(root,
+                        &RootWindowPropertyWatcherX::OnWindowXEventThunk,
+                        this);
+}
+
+RootWindowPropertyWatcherX::~RootWindowPropertyWatcherX() {
+  gdk_window_remove_filter(NULL,
+                           &RootWindowPropertyWatcherX::OnWindowXEventThunk,
+                           this);
+}
+
+GdkFilterReturn RootWindowPropertyWatcherX::OnWindowXEvent(
+    GdkXEvent* xevent, GdkEvent* event) {
+  XEvent* xev = static_cast<XEvent*>(xevent);
+
+  if (xev->xany.type == PropertyNotify) {
+    if (xev->xproperty.atom == ActiveWindowWatcherX::GetPropertyAtom())
+      ActiveWindowWatcherX::Notify();
+    else if (xev->xproperty.atom == WorkAreaWatcherX::GetPropertyAtom())
+      WorkAreaWatcherX::Notify();
+  }
+
+  return GDK_FILTER_CONTINUE;
+}
+
+}  // namespace internal
+
+}  // namespace ui