ui/events/platform/platform_event_source.cc

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #include "ui/events/platform/platform_event_source.h"
   6
   7 #include <algorithm>
   8
   9 #include "base/message_loop/message_loop.h"
  10 #include "ui/events/platform/platform_event_dispatcher.h"
  11 #include "ui/events/platform/platform_event_observer.h"
  12 #include "ui/events/platform/scoped_event_dispatcher.h"
  13
  14 namespace ui {
  15
  16 // static
  17 PlatformEventSource* PlatformEventSource::instance_ = NULL;
  18
  19 PlatformEventSource::PlatformEventSource()
  20     : overridden_dispatcher_(NULL),
  21       overridden_dispatcher_restored_(false) {
  22   CHECK(!instance_) << "Only one platform event source can be created.";
  23   instance_ = this;
  24 }
  25
  26 PlatformEventSource::~PlatformEventSource() {
  27   CHECK_EQ(this, instance_);
  28   instance_ = NULL;
  29 }
  30
  31 PlatformEventSource* PlatformEventSource::GetInstance() { return instance_; }
  32
  33 void PlatformEventSource::AddPlatformEventDispatcher(
  34     PlatformEventDispatcher* dispatcher) {
  35   CHECK(dispatcher);
  36   dispatchers_.AddObserver(dispatcher);
  37   OnDispatcherListChanged();
  38 }
  39
  40 void PlatformEventSource::RemovePlatformEventDispatcher(
  41     PlatformEventDispatcher* dispatcher) {
  42   dispatchers_.RemoveObserver(dispatcher);
  43   OnDispatcherListChanged();
  44 }
  45
  46 scoped_ptr<ScopedEventDispatcher> PlatformEventSource::OverrideDispatcher(
  47     PlatformEventDispatcher* dispatcher) {
  48   CHECK(dispatcher);
  49   overridden_dispatcher_restored_ = false;
  50   return make_scoped_ptr(
  51       new ScopedEventDispatcher(&overridden_dispatcher_, dispatcher));
  52 }
  53
  54 void PlatformEventSource::StopCurrentEventStream() {
  55 }
  56
  57 void PlatformEventSource::AddPlatformEventObserver(
  58     PlatformEventObserver* observer) {
  59   CHECK(observer);
  60   observers_.AddObserver(observer);
  61 }
  62
  63 void PlatformEventSource::RemovePlatformEventObserver(
  64     PlatformEventObserver* observer) {
  65   observers_.RemoveObserver(observer);
  66 }
  67
  68 uint32_t PlatformEventSource::DispatchEvent(PlatformEvent platform_event) {
  69   uint32_t action = POST_DISPATCH_PERFORM_DEFAULT;
  70
  71   FOR_EACH_OBSERVER(PlatformEventObserver, observers_,
  72                     WillProcessEvent(platform_event));
  73   // Give the overridden dispatcher a chance to dispatch the event first.
  74   if (overridden_dispatcher_)
  75     action = overridden_dispatcher_->DispatchEvent(platform_event);
  76
  77   if ((action & POST_DISPATCH_PERFORM_DEFAULT) &&
  78       dispatchers_.might_have_observers()) {
  79     base::ObserverList<PlatformEventDispatcher>::Iterator iter(&dispatchers_);
  80     while (PlatformEventDispatcher* dispatcher = iter.GetNext()) {
  81       if (dispatcher->CanDispatchEvent(platform_event))
  82         action = dispatcher->DispatchEvent(platform_event);
  83       if (action & POST_DISPATCH_STOP_PROPAGATION)
  84         break;
  85     }
  86   }
  87   FOR_EACH_OBSERVER(PlatformEventObserver, observers_,
  88                     DidProcessEvent(platform_event));
  89
  90   // If an overridden dispatcher has been destroyed, then the platform
  91   // event-source should halt dispatching the current stream of events, and wait
  92   // until the next message-loop iteration for dispatching events. This lets any
  93   // nested message-loop to unwind correctly and any new dispatchers to receive
  94   // the correct sequence of events.
  95   if (overridden_dispatcher_restored_)
  96     StopCurrentEventStream();
  97
  98   overridden_dispatcher_restored_ = false;
  99
 100   return action;
 101 }
 102
 103 void PlatformEventSource::OnDispatcherListChanged() {
 104 }
 105
 106 void PlatformEventSource::OnOverriddenDispatcherRestored() {
 107   CHECK(overridden_dispatcher_);
 108   overridden_dispatcher_restored_ = true;
 109 }
 110
 111 }  // namespace ui