mus: Server-side implementation of modal windows

components/mus/ws/event_dispatcher.h

 // Copyright 2015 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_EVENT_DISPATCHER_H_
 #define COMPONENTS_MUS_WS_EVENT_DISPATCHER_H_
 
 #include <stdint.h>
 
 #include <map>
@@ skipping 26 matching lines @@
   ~EventDispatcher() override;
 
   void set_root(ServerWindow* root) { root_ = root; }
 
   void set_surface_id(cc::SurfaceId surface_id) { surface_id_ = surface_id; }
 
   // |capture_window_| will receive all input. See window_tree.mojom for
   // details.
   ServerWindow* capture_window() { return capture_window_; }
   const ServerWindow* capture_window() const { return capture_window_; }
-  void SetCaptureWindow(ServerWindow* capture_window, bool in_nonclient_area);
+  // Setting capture can fail if the window is blocked by a modal window
+  // (indicated by returning |false|).
+  bool SetCaptureWindow(ServerWindow* capture_window, bool in_nonclient_area);
 
   // Retrieves the ServerWindow of the last mouse move.
   ServerWindow* mouse_cursor_source_window() const {
     return mouse_cursor_source_window_;
   }
 
   // Possibly updates the cursor. If we aren't in an implicit capture, we take
   // the last known location of the mouse pointer, and look for the
   // ServerWindow* under it.
   void UpdateCursorProviderByLastKnownLocation();
@@ skipping 118 matching lines @@
   // cancel or up.
   PointerIdToTargetMap pointer_targets_;
 
   DISALLOW_COPY_AND_ASSIGN(EventDispatcher);
 };
 
 }  // namespace ws
 }  // namespace mus
 
 #endif  // COMPONENTS_MUS_WS_EVENT_DISPATCHER_H_