mus: Server-side implementation of modal windows

components/mus/public/interfaces/window_tree.mojom

 // 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.
 
 module mus.mojom;
 
 import "components/mus/public/interfaces/compositor_frame.mojom";
 import "components/mus/public/interfaces/cursor.mojom";
 import "components/mus/public/interfaces/input_events.mojom";
 import "components/mus/public/interfaces/mus_constants.mojom";
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   // . |window_id| or |transient_window_id| does not identify a valid window.
   // . |transient_window_id| is an ancestor of |window_id|.
   AddTransientWindow(uint32 change_id,
                      uint32 window_id,
                      uint32 transient_window_id);
 
   // Decouples the lifetime of |transient_window_id| from its transient parent.
   // This does not change transient window's position in the window hierarchy.
   RemoveTransientWindowFromParent(uint32 change_id, uint32 transient_window_id);
 
+  // Sets |window_id| to be modal to its transient parent.
+  // This fails if |window_id| does not identify a valid window.
+  // TODO(mohsen): If |window_id| does not have a transient parent, this will
+  // have no effect. Plan is to make a window modal to system if it does not
+  // have a transient parent.
+  SetModal(uint32 change_id, uint32 window_id);
+
   // Reorders a window in its parent, relative to |relative_window_id| according
   // to |direction|. Only the connection that created the window's parent can
   // reorder its children.
   ReorderWindow(uint32 change_id,
                 uint32 window_id,
                 uint32 relative_window_id,
                 OrderDirection direction);
 
   // Returns the windows comprising the tree starting at |window_id|.
   // |window_id| is the first result in the return value, unless |window_id| is
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   // See description of WindowManager for details.
   GetWindowManager(associated WindowManager& internal);
 };
 
 // Mus provides this interface as a way for clients to connect and obtain a
 // WindowTree handle with a supplied WindowTreeClient handle. The
 // WindowTreeClient has no roots, use NewTopLevelWindow() to create one.
 interface WindowTreeFactory {
   CreateWindowTree(WindowTree& tree_request, WindowTreeClient client);
 };