Split cursor location from UserDisplayManager.

services/ui/ws/cursor_location_manager.h

+// Copyright 2017 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 SERVICES_UI_WS_CURSOR_LOCATION_MANAGER_H_
+#define SERVICES_UI_WS_CURSOR_LOCATION_MANAGER_H_
+
+#include "base/atomicops.h"
+#include "base/macros.h"
+#include "mojo/public/cpp/system/buffer.h"
+
+namespace gfx {
+class Point;
+}
+
+namespace ui {
+namespace ws {
+
+// Manages a shared memory buffer that stores the cursor location.
+class CursorLocationManager {
+ public:
+  CursorLocationManager();
+  ~CursorLocationManager();
+
+  // Sets the current cursor location to |point|. Atomically writes the location
+  // to shared memory.
+  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:
+  base::subtle::Atomic32* cursor_location_memory() {
+    return reinterpret_cast<base::subtle::Atomic32*>(
+        cursor_location_mapping_.get());
+  }
+
+  // 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_ = 0;
+
+  // A handle to a shared memory buffer that is one 32 bit integer long. We
+  // share this with any client 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.)
+  mojo::ScopedSharedBufferMapping cursor_location_mapping_;
+
+  DISALLOW_COPY_AND_ASSIGN(CursorLocationManager);
+};
+
+}  // namespace ws
+}  // namespace ui
+
+#endif  // SERVICES_UI_WS_CURSOR_LOCATION_MANAGER_H_