Views:: Make Labels support text selection.

ui/views/selection_controller_delegate.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 UI_VIEWS_SELECTION_CONTROLLER_DELEGATE_H_
 #define UI_VIEWS_SELECTION_CONTROLLER_DELEGATE_H_
 
 #include "ui/views/views_export.h"
 
 namespace ui {
 class MouseEvent;
 }
 
 namespace views {
 
 // An interface implemented/managed by a view which uses the
 // SelectionController.
 class VIEWS_EXPORT SelectionControllerDelegate {
  public:
   // Returns the associated RenderText instance to be used for selection.
   virtual gfx::RenderText* GetRenderTextForSelectionController() = 0;
 
   // Methods related to properties of the associated view.
 
   // Returns true if the associated text view is read only.
   virtual bool IsReadOnly() const = 0;
+  // Returns whether the associated view supports drag-and-drop.
+  virtual bool SupportsDrag() const = 0;
   // Returns whether there is a drag operation originating from the associated
   // view.
   virtual bool HasTextBeingDragged() const = 0;
-  // Sets whether text is being dragged from the associated view.
+  // Sets whether text is being dragged from the associated view. Called only if
+  // the delegate supports drag.
   virtual void SetTextBeingDragged(bool value) = 0;
   // Returns the height of the associated view.
   virtual int GetViewHeight() const = 0;
   // Returns the width of the associated view.
   virtual int GetViewWidth() const = 0;
   // Returns the drag selection timer delay. This is the duration after which a
   // drag selection is updated when the event location is outside the text
   // bounds.
   virtual int GetDragSelectionDelay() const = 0;
 
@@ skipping 17 matching lines @@
   // the render text instance, it may be called outside of a pointer action.
   virtual void UpdateSelectionClipboard() = 0;
 
  protected:
   virtual ~SelectionControllerDelegate() {}
 };
 
 }  // namespace views
 
 #endif  // UI_VIEWS_SELECTION_CONTROLLER_DELEGATE_H_