MacViews: Implement capture using NSEvent local+global monitors

ui/views/cocoa/cocoa_mouse_capture.h

+// Copyright 2014 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 UI_VIEWS_COCOA_COCOA_MOUSE_CAPTURE_H_
+#define UI_VIEWS_COCOA_COCOA_MOUSE_CAPTURE_H_
+
+#include "base/macros.h"
+#include "base/memory/scoped_ptr.h"
+#include "ui/views/views_export.h"
+
+namespace views {
+
+class CocoaMouseCaptureDelegate;
+
+// Basic mouse capture to simulate ::SetCapture() from Windows. This is used to
+// support menu widgets (e.g. on Combo boxes). Clicking anywhere other than the
+// menu should dismiss the menu and "swallow" the mouse event. All events are
+// forwarded, but only events to the same application are "swallowed", which is
+// consistent with how native NSMenus behave.
+class VIEWS_EXPORT CocoaMouseCapture {
+ public:
+  explicit CocoaMouseCapture(CocoaMouseCaptureDelegate* delegate);
+  ~CocoaMouseCapture();
+
+  // True if the event tap is active (i.e. not stolen by a later instance).
+  bool IsActive() const { return active_handle_; }
+
+ private:
+  class ActiveEventTap;
+
+  // Deactivates the event tap if still active.
+  void OnOtherClientGotCapture();
+
+  CocoaMouseCaptureDelegate* delegate_;  // Weak. Owns this.
+
+  // The active event tap for this capture. Owned by this, but can be cleared
+  // out early if another instance of CocoaMouseCapture is created.
+  scoped_ptr<ActiveEventTap> active_handle_;
+
+  DISALLOW_COPY_AND_ASSIGN(CocoaMouseCapture);
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_COCOA_COCOA_MOUSE_CAPTURE_H_