Block internal PlatformEvents before they are dispatched in touchview.

ui/events/platform/platform_event_source.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/events/platform/platform_event_source.h"
 
 #include <algorithm>
 
 #include "base/message_loop/message_loop.h"
 #include "ui/events/platform/platform_event_dispatcher.h"
+#include "ui/events/platform/platform_event_filter.h"
 #include "ui/events/platform/platform_event_observer.h"
 #include "ui/events/platform/scoped_event_dispatcher.h"
 
 namespace ui {
 
 // static
 PlatformEventSource* PlatformEventSource::instance_ = NULL;
 
 PlatformEventSource::PlatformEventSource()
     : overridden_dispatcher_(NULL),
@@ skipping 34 matching lines @@
     PlatformEventObserver* observer) {
   CHECK(observer);
   observers_.AddObserver(observer);
 }
 
 void PlatformEventSource::RemovePlatformEventObserver(
     PlatformEventObserver* observer) {
   observers_.RemoveObserver(observer);
 }
 
+void PlatformEventSource::AddPlatformEventFilter(PlatformEventFilter* filter) {
+  CHECK(filter);
+  filters_.AddObserver(filter);
+}
+
+void PlatformEventSource::RemovePlatformEventFilter(
+    PlatformEventFilter* filter) {
+  filters_.RemoveObserver(filter);
+}
+
 uint32_t PlatformEventSource::DispatchEvent(PlatformEvent platform_event) {
   uint32_t action = POST_DISPATCH_PERFORM_DEFAULT;
 
+  // Always deliver all events to all PlatformEventFilters, if any of them
+  // specify that the event should not be dispatched, return immediately to
+  // stop propagation.
+  ObserverList<PlatformEventFilter>::Iterator iter(filters_);
+  while (PlatformEventFilter* filter = iter.GetNext()) {
+    if (!filter->ShouldDispatchEvent(platform_event))
+      action = POST_DISPATCH_STOP_PROPAGATION;
+  }
+  if (action == POST_DISPATCH_STOP_PROPAGATION)
+    return action;
+
   FOR_EACH_OBSERVER(PlatformEventObserver, observers_,
                     WillProcessEvent(platform_event));
   // Give the overridden dispatcher a chance to dispatch the event first.
   if (overridden_dispatcher_)
     action = overridden_dispatcher_->DispatchEvent(platform_event);
 
   if ((action & POST_DISPATCH_PERFORM_DEFAULT) &&
       dispatchers_.might_have_observers()) {
     ObserverList<PlatformEventDispatcher>::Iterator iter(dispatchers_);
     while (PlatformEventDispatcher* dispatcher = iter.GetNext()) {
@@ skipping 24 matching lines @@
 
 void PlatformEventSource::OnDispatcherListChanged() {
 }
 
 void PlatformEventSource::OnOverriddenDispatcherRestored() {
   CHECK(overridden_dispatcher_);
   overridden_dispatcher_restored_ = true;
 }
 
 }  // namespace ui