mus: Implement ScreenMus::GetCursorScreenPoint().

components/mus/ws/window_manager_state.cc

Index: components/mus/ws/window_manager_state.cc
diff --git a/components/mus/ws/window_manager_state.cc b/components/mus/ws/window_manager_state.cc
index 7fc9bd2556f0b80562c7b4eb5b9c1fa5fef1e4a4..d741d0d03593319b2a339a9bef596f714978858a 100644
--- a/components/mus/ws/window_manager_state.cc
+++ b/components/mus/ws/window_manager_state.cc
@@ -165,6 +165,43 @@ void WindowManagerState::OnWillDestroyTree(WindowTree* tree) {
                                            : mojom::EventResult::UNHANDLED);
 }
 
+mojo::ScopedSharedBufferHandle WindowManagerState::GetCursorLocationMemory() {

[sky, 2016/04/27 20:10:28]

If you put this code here, it means we're only get the coordinates of one
display. I think the right place for this is UserDisplayManager, which you can
get by way of:

window_server()->display_manager()->GetUserDisplayManager(user_id_);

+  if (!cursor_location_memory_) {
+    // Create our shared memory segment to share the cursor state with our
+    // window clients.
+    MojoResult result = mojo::CreateSharedBuffer(nullptr,
+                                                 sizeof(base::subtle::Atomic32),
+                                                 &cursor_location_handle_);
+    if (result != MOJO_RESULT_OK)
+      return mojo::ScopedSharedBufferHandle();
+    DCHECK(cursor_location_handle_.is_valid());
+
+    result = mojo::MapBuffer(cursor_location_handle_.get(), 0,
+                             sizeof(base::subtle::Atomic32),
+                             reinterpret_cast<void**>(&cursor_location_memory_),
+                             MOJO_MAP_BUFFER_FLAG_NONE);
+    if (result != MOJO_RESULT_OK)
+      return mojo::ScopedSharedBufferHandle();
+    DCHECK(cursor_location_memory_);
+
+    base::subtle::NoBarrier_Store(cursor_location_memory_,
+                                  current_cursor_location_);
+  }
+
+  mojo::ScopedSharedBufferHandle duped;
+  MojoDuplicateBufferHandleOptions options = {
+    sizeof(MojoDuplicateBufferHandleOptions),
+    MOJO_DUPLICATE_BUFFER_HANDLE_OPTIONS_FLAG_READ_ONLY
+  };
+  MojoResult result = mojo::DuplicateBuffer(cursor_location_handle_.get(),
+                                            &options, &duped);
+  if (result != MOJO_RESULT_OK)
+    return mojo::ScopedSharedBufferHandle();
+  DCHECK(duped.is_valid());
+
+  return duped;
+}
+
 WindowManagerState::WindowManagerState(Display* display,
                                        PlatformDisplay* platform_display,
                                        cc::SurfaceId surface_id,
@@ -174,7 +211,9 @@ WindowManagerState::WindowManagerState(Display* display,
       platform_display_(platform_display),
       is_user_id_valid_(is_user_id_valid),
       user_id_(user_id),
-      event_dispatcher_(this) {
+      event_dispatcher_(this),
+      current_cursor_location_(0),
+      cursor_location_memory_(nullptr) {
   frame_decoration_values_ = mojom::FrameDecorationValues::New();
   frame_decoration_values_->normal_client_area_insets = mojo::Insets::New();
   frame_decoration_values_->maximized_client_area_insets = mojo::Insets::New();
@@ -369,6 +408,17 @@ void WindowManagerState::OnServerWindowCaptureLost(ServerWindow* window) {
   window_server()->ProcessLostCapture(window);
 }
 
+void WindowManagerState::OnMouseCursorLocationChanged(
+    const gfx::Point& point) {
+  current_cursor_location_ =
+      static_cast<base::subtle::Atomic32>(
+          (point.x() & 0xFFFF) << 16 | (point.y() & 0xFFFF));
+  if (cursor_location_memory_) {
+    base::subtle::NoBarrier_Store(cursor_location_memory_,
+                                  current_cursor_location_);
+  }
+}
+
 void WindowManagerState::DispatchInputEventToWindow(ServerWindow* target,
                                                     bool in_nonclient_area,
                                                     const ui::Event& event,