mus: Implement ScreenMus::GetCursorScreenPoint().

components/mus/ws/user_display_manager.h

 // Copyright 2016 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.
 
 #ifndef COMPONENTS_MUS_WS_USER_DISPLAY_MANAGER_H_
 #define COMPONENTS_MUS_WS_USER_DISPLAY_MANAGER_H_
 
 #include <set>
 
+#include "base/atomicops.h"
 #include "base/macros.h"
 #include "components/mus/public/interfaces/display.mojom.h"
 #include "components/mus/ws/user_id.h"
 #include "mojo/public/cpp/bindings/binding_set.h"
 #include "mojo/public/cpp/bindings/interface_ptr_set.h"
 
+namespace gfx {
+class Point;
+}
+
 namespace mus {
 namespace ws {
 
 class Display;
 class DisplayManager;
 class WindowManagerState;
 
 namespace test {
 class UserDisplayManagerTestApi;
 }
 
 // Provides per user display state.
 class UserDisplayManager : public mojom::DisplayManager {
  public:
   UserDisplayManager(ws::DisplayManager* display_manager,
                      const UserId& user_id);
   ~UserDisplayManager() override;
 
   void OnFrameDecorationValuesChanged(WindowManagerState* wms);
 
   void AddDisplayManagerBinding(
       mojo::InterfaceRequest<mojom::DisplayManager> request);
 
   // Called by Display prior to |display| being removed and destroyed.
   void OnWillDestroyDisplay(Display* display);
 
+  // Called from WindowManagerState when its EventDispatcher receives a mouse
+  // event.
+  void OnMouseCursorLocationChanged(const gfx::Point& point);
+
+  // Returns a read-only handle to the shared memory which contains the global
+  // mouse cursor position. Each call returns a new handle.
+  mojo::ScopedSharedBufferHandle GetCursorLocationMemory();
+
  private:
   friend class test::UserDisplayManagerTestApi;
 
   // Returns the WindowManagerStates for the associated user that have frame
   // decoration values.
   std::set<const WindowManagerState*> GetWindowManagerStatesForUser() const;
 
   void OnObserverAdded(mojom::DisplayManagerObserver* observer);
 
   // Calls OnDisplays() on |observer|.
@@ skipping 15 matching lines @@
 
   mojo::BindingSet<mojom::DisplayManager> display_manager_bindings_;
 
   // WARNING: only use these once |got_valid_frame_decorations_| is true.
   mojo::InterfacePtrSet<mojom::DisplayManagerObserver>
       display_manager_observers_;
 
   // Observer used for tests.
   mojom::DisplayManagerObserver* test_observer_ = nullptr;
 
+  // The current location of the cursor. This is always kept up to date so we
+  // can atomically write this to |cursor_location_memory_| once it is created.
+  base::subtle::Atomic32 current_cursor_location_;
+
+  // A handle to a shared memory buffer that is one 64 bit integer long. We
+  // share this with any connection as the same user. This buffer is lazily
+  // created on the first access.
+  mojo::ScopedSharedBufferHandle cursor_location_handle_;
+
+  // The one int32 in |cursor_location_handle_|. When we write to this
+  // location, we must always write to it atomically. (On the other side of the
+  // mojo connection, this data must be read atomically.)
+  base::subtle::Atomic32* cursor_location_memory_;
+
   DISALLOW_COPY_AND_ASSIGN(UserDisplayManager);
 };
 
 }  // namespace ws
 }  // namespace mus
 
 #endif  // COMPONENTS_MUS_WS_USER_DISPLAY_MANAGER_H_