ui/views/input_event_activation_protector.h

// Copyright 2018 The Chromium Authors
// Use of this source code is governed by a BSD-style license that can be
// found in the LICENSE file.

#ifndef UI_VIEWS_INPUT_EVENT_ACTIVATION_PROTECTOR_H_
#define UI_VIEWS_INPUT_EVENT_ACTIVATION_PROTECTOR_H_

#include "base/time/time.h"
#include "ui/views/views_export.h"
#include "ui/views/windows_stationarity_monitor.h"

namespace ui {
class Event;
}

namespace views {

// The goal of this class is to prevent potentially unintentional user
// interaction with a UI element.
// See switch kDisableInputEventActivationProtectionForTesting for disabling it.
class VIEWS_EXPORT InputEventActivationProtector
    : WindowsStationarityMonitor::Observer {
 public:
  InputEventActivationProtector();
  ~InputEventActivationProtector() override;

  InputEventActivationProtector(const InputEventActivationProtector&) = delete;
  InputEventActivationProtector& operator=(
      const InputEventActivationProtector&) = delete;

  // Updates the state of the protector based off of visibility changes. This
  // method must be called when the visibility of the view is changed.
  void VisibilityChanged(bool is_visible);

  // Updates the |view_protected_time_stamp_| if needed. This function will be
  // called when we want to reset back the input protector to "initial
  // protected" state, basically under some certain view's proprieties changed
  // events.
  //
  // If |force| is true, force to update the |view_protected_time_stamp_| even
  // earlier (shortly before the owner view is visible). It usually helps us to
  // prevent unintentional clicks happening when "visibility changes" event
  // coming later than click event (for example click event -> tab activation ->
  // visibility change).
  void MaybeUpdateViewProtectedTimeStamp(bool force = false);

  // Returns true if the event is a mouse, touch, or pointer event that took
  // place within the double-click time interval after
  // |view_protected_time_stamp_|.
  virtual bool IsPossiblyUnintendedInteraction(const ui::Event& event);

  // Implements WindowsStationarityMonitor::Observer:
  void OnWindowStationaryStateChanged() override;

  // Resets the state for click tracking.
  void ResetForTesting();

 private:
  // Timestamp of when the view was initially protected. Used to prevent
  // unintentional user interaction event immediately from the timestamp.
  base::TimeTicks view_protected_time_stamp_;
  // Timestamp of the last event.
  base::TimeTicks last_event_timestamp_;
  // Number of repeated UI events with short intervals.
  size_t repeated_event_count_ = 0;
};

}  // namespace views

#endif  // UI_VIEWS_INPUT_EVENT_ACTIVATION_PROTECTOR_H_