Draggable peeking/fullscreen launcher with transparent background.

ash/shelf/wm_shelf.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 ASH_SHELF_WM_SHELF_H_
 #define ASH_SHELF_WM_SHELF_H_
 
 #include <memory>
 
 #include "ash/ash_export.h"
@@ skipping 79 matching lines @@
   void SetAutoHideBehavior(ShelfAutoHideBehavior behavior);
 
   ShelfAutoHideState GetAutoHideState() const;
 
   // Invoke when the auto-hide state may have changed (for example, when the
   // system tray bubble opens it should force the shelf to be visible).
   void UpdateAutoHideState();
 
   ShelfBackgroundType GetBackgroundType() const;
 
+  // Sets the shelf background to translucent while the app list is active in
+  // order to prevent overlapping opaque backgrounds.
+  void AppListIsActive(bool hideBackground);

[vadimt, 2017/05/22 23:36:56]

Should be called something like SetBackgroundOpacity?

[newcomer, 2017/05/25 23:10:51]

It just lets the ShelfLayoutManager know that the applist is active in order to
restrict the background behavior (so it doesn't strictly speaking set the
opacity). Updated comment! LMK if you still think it should be renamed.

+
   void UpdateVisibilityState();
 
   ShelfVisibilityState GetVisibilityState() const;
 
   // Returns the ideal bounds of the shelf assuming it is visible.
   gfx::Rect GetIdealBounds();
 
   gfx::Rect GetUserWorkAreaBounds() const;
 
   // Updates the icon position given the current window bounds. This is used
@@ skipping 55 matching lines @@
   base::ObserverList<WmShelfObserver> observers_;
 
   // Forwards mouse and gesture events to ShelfLayoutManager for auto-hide.
   // TODO(mash): Facilitate simliar functionality in mash: crbug.com/631216
   std::unique_ptr<AutoHideEventHandler> auto_hide_event_handler_;
 
   // Forwards touch gestures on a bezel sensor to the shelf.
   // TODO(mash): Facilitate simliar functionality in mash: crbug.com/636647
   std::unique_ptr<ShelfBezelEventHandler> bezel_event_handler_;
 
+  // Set with AppListIsActive, blocks SetPaintsBackground from painting a
+  // transparent background while the app list is active, which prevents the
+  // two transparent backgrounds from overlapping.
+  bool app_list_is_active_ = false;
+
   DISALLOW_COPY_AND_ASSIGN(WmShelf);
 };
 
 }  // namespace ash
 
 #endif  // ASH_SHELF_WM_SHELF_H_