ui/events/gesture_detection/snap_scroll_controller.h

   1 // Copyright 2014 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef UI_EVENTS_GESTURE_DETECTION_SNAP_SCROLL_CONTROLLER_H_
   6 #define UI_EVENTS_GESTURE_DETECTION_SNAP_SCROLL_CONTROLLER_H_
   7
   8 #include "base/basictypes.h"
   9 #include "ui/events/gesture_detection/gesture_detection_export.h"
  10
  11 namespace gfx {
  12 class Display;
  13 }
  14
  15 namespace ui {
  16
  17 class MotionEvent;
  18 class ZoomManager;
  19
  20 // Port of SnapScrollController.java from Chromium
  21 // Controls the scroll snapping behavior based on scroll updates.
  22 class SnapScrollController {
  23  public:
  24   explicit SnapScrollController(const gfx::Display& display);
  25   ~SnapScrollController();
  26
  27   // Updates the snap scroll mode based on the given X and Y distance to be
  28   // moved on scroll.  If the scroll update is above a threshold, the snapping
  29   // behavior is reset.
  30   void UpdateSnapScrollMode(float distance_x, float distance_y);
  31
  32   // Sets the snap scroll mode based on the event type.
  33   void SetSnapScrollingMode(const MotionEvent& event,
  34                             bool is_scale_gesture_detection_in_progress);
  35
  36   void ResetSnapScrollMode() { snap_scroll_mode_ = SNAP_NONE; }
  37   bool IsSnapVertical() const { return snap_scroll_mode_ == SNAP_VERT; }
  38   bool IsSnapHorizontal() const { return snap_scroll_mode_ == SNAP_HORIZ; }
  39   bool IsSnappingScrolls() const { return snap_scroll_mode_ != SNAP_NONE; }
  40
  41  private:
  42   enum SnapMode {
  43     SNAP_NONE,
  44     SNAP_HORIZ,
  45     SNAP_VERT
  46   };
  47
  48   float channel_distance_;
  49   SnapMode snap_scroll_mode_;
  50   float first_touch_x_;
  51   float first_touch_y_;
  52   float distance_x_;
  53   float distance_y_;
  54
  55   DISALLOW_COPY_AND_ASSIGN(SnapScrollController);
  56 };
  57
  58 }  // namespace ui
  59
  60 #endif  // UI_EVENTS_GESTURE_DETECTION_SNAP_SCROLL_CONTROLLER_H_