mus: Implement Window Server Capture

components/mus/ws/event_dispatcher.cc

Index: components/mus/ws/event_dispatcher.cc
diff --git a/components/mus/ws/event_dispatcher.cc b/components/mus/ws/event_dispatcher.cc
index 2df70cadcf6cb314cdf9ee42e91d4fa687e30194..1daa3b87f300b2eea35e4f7a86a03cc622b909e6 100644
--- a/components/mus/ws/event_dispatcher.cc
+++ b/components/mus/ws/event_dispatcher.cc
@@ -141,16 +141,19 @@ class EventMatcher {
 ////////////////////////////////////////////////////////////////////////////////
 
 EventDispatcher::EventDispatcher(EventDispatcherDelegate* delegate)
-    : delegate_(delegate), root_(nullptr) {}
+    : delegate_(delegate), root_(nullptr), capture_window_(nullptr) {}
 
 EventDispatcher::~EventDispatcher() {
-  std::set<ServerWindow*> pointer_targets;
-  for (const auto& pair : pointer_targets_) {
-    if (pair.second.window &&
-        pointer_targets.insert(pair.second.window).second) {
-      pair.second.window->RemoveObserver(this);
-    }
-  }
+  CancelAllPointerEvents();
+}
+
+void EventDispatcher::SetCaptureWindow(ServerWindow* window) {
+  // Cancel all implicit captures.
+  CancelAllPointerEvents();

[sky, 2015/11/17 01:06:42]

If window is in pointer_targets_ won't this incorrectly remove it?

+  capture_window_ = window;
+  // Track the lifetime of the window with explicit capture.
+  if (window)
+    window->AddObserver(this);
 }
 
 void EventDispatcher::AddAccelerator(uint32_t id,
@@ -205,6 +208,13 @@ void EventDispatcher::ProcessKeyEvent(mojom::EventPtr event) {
 }
 
 void EventDispatcher::ProcessPointerEvent(mojom::EventPtr event) {
+  if (capture_window_) {
+    PointerTarget pointer_target;
+    pointer_target.window = capture_window_;
+    DispatchToPointerTarget(pointer_target, event.Pass());
+    return;
+  }
+
   const int32_t pointer_id = event->pointer_data->pointer_id;
   if (event->action == mojom::EVENT_TYPE_WHEEL ||
       (event->action == mojom::EVENT_TYPE_POINTER_MOVE &&
@@ -272,8 +282,31 @@ void EventDispatcher::DispatchToPointerTarget(const PointerTarget& target,
                                         event.Pass());
 }
 
+void EventDispatcher::CancelAllPointerEvents() {
+  if (capture_window_) {

[sky, 2015/11/17 01:06:42]

Based on the name I wouldn't expect this to reset capture_window_ too.

+    capture_window_->RemoveObserver(this);
+    capture_window_ = nullptr;
+  }
+  std::set<ServerWindow*> pointer_targets;

[sky, 2015/11/17 01:06:42]

The windows should see a cancel when this happens.

+  for (const auto& pair : pointer_targets_) {
+    if (pair.second.window &&
+        pointer_targets.insert(pair.second.window).second) {
+      pair.second.window->RemoveObserver(this);
+    }
+  }
+  pointer_targets_.clear();
+}
+
 void EventDispatcher::CancelPointerEventsToTarget(ServerWindow* window) {
   window->RemoveObserver(this);
+  if (capture_window_ == window) {
+    capture_window_ = nullptr;
+    // A window only cares to be informed that it lost capture if it explicitly
+    // requested capture. A window can lose capture if another window gains
+    // explicit capture.
+    delegate_->OnLostCapture(window);
+    return;
+  }
 
   for (auto& pair : pointer_targets_) {
     if (pair.second.window == window)