Views: Extract text selection code from Textfield.

ui/views/selection_controller.h

Index: ui/views/selection_controller.h
diff --git a/ui/views/selection_controller.h b/ui/views/selection_controller.h
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+++ b/ui/views/selection_controller.h
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+// 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_H_
+#define UI_VIEWS_SELECTION_CONTROLLER_H_
+
+#include "base/time/time.h"
+#include "base/timer/timer.h"
+#include "ui/gfx/geometry/point.h"
+#include "ui/gfx/range/range.h"
+#include "ui/gfx/selection_model.h"
+#include "ui/views/views_export.h"
+
+namespace gfx {
+class RenderText;
+}
+
+namespace ui {
+class MouseEvent;
+}
+
+namespace views {
+class SelectionControllerDelegate;
+
+// Helper class used to facilitate mouse event handling and text selection. To
+// use, clients must implement the SelectionControllerDelegate interface.
+class VIEWS_EXPORT SelectionController {
+ public:
+  // |delegate| must be non-null.
+  explicit SelectionController(SelectionControllerDelegate* delegate);
+
+  // Handle mouse events forwarded by |delegate_|. |handled| specifies whether
+  // the event has already been handled by the |delegate_|. If |handled| is
+  // true, the mouse event is just used to update the internal state without
+  // updating the state of the associated RenderText instance.
+  bool OnMousePressed(const ui::MouseEvent& event, bool handled);
+  bool OnMouseDragged(const ui::MouseEvent& event);
+  void OnMouseReleased(const ui::MouseEvent& event);
+
+  // Returns the latest click location.
+  gfx::Point last_click_location() const { return last_click_location_; }
+
+ private:
+  // Tracks the mouse clicks for single/double/triple clicks.
+  void TrackMouseClicks(const ui::MouseEvent& event);
+
+  // Returns the associated render text instance via the |delegate_|.
+  gfx::RenderText* GetRenderText();
+
+  // Helper function to update the selection on a mouse drag as per
+  // |last_drag_location_|. Can be called asynchronously, through a timer.
+  void SelectThroughLastDragLocation();
+
+  // A timer and point used to modify the selection when dragging.
+  base::RepeatingTimer drag_selection_timer_;
+  gfx::Point last_drag_location_;
+
+  // State variables used to track double and triple clicks.
+  base::TimeTicks last_click_time_;
+  gfx::Point last_click_location_;
+  size_t aggregated_clicks_;
+  gfx::Range double_click_word_;
+
+  // Weak pointer.
+  SelectionControllerDelegate* delegate_;
+
+  DISALLOW_COPY_AND_ASSIGN(SelectionController);
+};
+
+}  // namespace views
+
+#endif  // UI_VIEWS_SELECTION_CONTROLLER_H_