Support longpress drag selection

ui/touch_selection/longpress_drag_selector.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 UI_TOUCH_SELECTION_LONGPRESS_DRAG_SELECTOR_H_
+#define UI_TOUCH_SELECTION_LONGPRESS_DRAG_SELECTOR_H_
+
+#include "base/time/time.h"
+#include "ui/gfx/geometry/point_f.h"
+#include "ui/gfx/geometry/vector2d_f.h"
+#include "ui/touch_selection/touch_selection_draggable.h"
+#include "ui/touch_selection/ui_touch_selection_export.h"
+
+namespace ui {
+
+class MotionEvent;
+
+class UI_TOUCH_SELECTION_EXPORT LongPressDragSelectorClient
+    : public TouchSelectionDraggableClient {
+ public:
+  ~LongPressDragSelectorClient() override {}
+  virtual void OnLongPressDragActiveStateChanged() = 0;
+  virtual gfx::PointF GetSelectionStart() const = 0;
+  virtual gfx::PointF GetSelectionEnd() const = 0;
+};
+
+// Supports text selection via touch dragging after a longpress-initiated
+// selection.
+class UI_TOUCH_SELECTION_EXPORT LongPressDragSelector
+    : public TouchSelectionDraggable {
+ public:
+  explicit LongPressDragSelector(LongPressDragSelectorClient* client);
+  ~LongPressDragSelector() override;
+
+  // TouchSelectionDraggable implementation.
+  bool WillHandleTouchEvent(const MotionEvent& event) override;
+  bool IsActive() const override;
+
+  // Called just prior to a longpress event being handled.
+  void OnLongPressEvent(base::TimeTicks event_time,
+                        const gfx::PointF& position);
+
+  // Called when the active selection changes.
+  void OnSelectionActivated();
+  void OnSelectionDeactivated();
+
+ private:
+  enum SelectionState {
+    INACTIVE,
+    LONGPRESS_PENDING,
+    SELECTION_PENDING,
+    DRAG_PENDING,
+    DRAGGING
+  };
+
+  void SetState(SelectionState state);
+
+  LongPressDragSelectorClient* const client_;
+
+  SelectionState state_;
+
+  base::TimeTicks touch_down_time_;
+  gfx::PointF touch_down_position_;
+
+  gfx::Vector2dF longpress_drag_selection_offset_;
+  gfx::PointF longpress_drag_start_anchor_;
+  bool has_longpress_drag_start_anchor_;
+};
+
+}  // namespace ui
+
+#endif  // UI_TOUCH_SELECTION_LONGPRESS_DRAG_SELECTOR_H_