mus: Let clients set the cursor of their window.

components/mus/ws/window_tree_host_impl.cc

Index: components/mus/ws/window_tree_host_impl.cc
diff --git a/components/mus/ws/window_tree_host_impl.cc b/components/mus/ws/window_tree_host_impl.cc
index 7360710d1e66021f04d47313a1bd18a1432f231d..e0d16873364c660696325edadb9ca5c035640cf9 100644
--- a/components/mus/ws/window_tree_host_impl.cc
+++ b/components/mus/ws/window_tree_host_impl.cc
@@ -7,6 +7,7 @@
 #include "base/debug/debugger.h"
 #include "base/strings/utf_string_conversions.h"
 #include "components/mus/common/types.h"
+#include "components/mus/public/interfaces/input_event_constants.mojom.h"
 #include "components/mus/ws/connection_manager.h"
 #include "components/mus/ws/display_manager.h"
 #include "components/mus/ws/focus_controller.h"
@@ -43,7 +44,8 @@ WindowTreeHostImpl::WindowTreeHostImpl(
       display_manager_(
           DisplayManager::Create(app_impl, gpu_state, surfaces_state)),
       window_manager_(window_manager.Pass()),
-      tree_awaiting_input_ack_(nullptr) {
+      tree_awaiting_input_ack_(nullptr),
+      last_cursor_(0) {
   display_manager_->Init(this);
   if (client_) {
     client_.set_connection_error_handler(base::Bind(
@@ -131,6 +133,11 @@ void WindowTreeHostImpl::SetImeVisibility(ServerWindow* window, bool visible) {
   display_manager_->SetImeVisibility(visible);
 }
 
+void WindowTreeHostImpl::OnCursorUpdated(ServerWindow* window) {
+  if (window == event_dispatcher_.last_targeted_window())

[sky, 2015/12/01 21:48:01]

Doesn't this need to be more sophisticated? What if the last event target is no
longer under the mouse?

[Elliot Glaysher, 2015/12/02 20:01:32]

So I might just be wrong about this, but in event_dispatcher.cc, we appear to
track implicit captures in EventDispatcher::ProcessPointerEvent() before it
passes to DispatchToPointerTarget, which actually sets this targeted window.

Is this insufficient?

[sky, 2015/12/02 21:19:41]

You are correct. We currently only have implicit capture.
There are a couple of cases that come to mind:
. press mouse, move mouse over another window. last_targeted_window is now the
wrong window, right?
. press and release mouse, z-order of windows changes, last_targeted_window is
now the wrong window.

+    UpdateNativeCursor(window->cursor());
+}
+
 void WindowTreeHostImpl::SetSize(mojo::SizePtr size) {
   display_manager_->SetViewportSize(size.To<gfx::Size>());
 }
@@ -211,6 +218,13 @@ void WindowTreeHostImpl::DispatchNextEventFromQueue() {
   event_dispatcher_.OnEvent(next_event.Pass());
 }
 
+void WindowTreeHostImpl::UpdateNativeCursor(int32_t cursor_id) {
+  if (cursor_id != last_cursor_) {
+    display_manager_->SetCursorById(cursor_id);
+    last_cursor_ = cursor_id;
+  }
+}
+
 ServerWindow* WindowTreeHostImpl::GetRootWindow() {
   return root_.get();
 }
@@ -360,6 +374,13 @@ void WindowTreeHostImpl::DispatchInputEventToWindow(ServerWindow* target,
                                                     bool in_nonclient_area,
                                                     mojom::EventPtr event) {
   DCHECK(!event_ack_timer_.IsRunning());
+  if (event->action == mojom::EventType::EVENT_TYPE_POINTER_CANCEL ||
+      event->action == mojom::EventType::EVENT_TYPE_POINTER_DOWN ||
+      event->action == mojom::EventType::EVENT_TYPE_POINTER_MOVE ||
+      event->action == mojom::EventType::EVENT_TYPE_POINTER_UP) {
+    UpdateNativeCursor(target->cursor());
+  }
+
   // If the event is in the non-client area the event goes to the owner of
   // the window. Otherwise if the window is an embed root, forward to the
   // embedded window.