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// Copyright 2014 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_EVENTS_GESTURE_DETECTION_SCALE_GESTURE_DETECTOR_H_
#define UI_EVENTS_GESTURE_DETECTION_SCALE_GESTURE_DETECTOR_H_
#include "base/time/time.h"
#include "ui/events/gesture_detection/gesture_detection_export.h"
namespace ui {
class MotionEvent;
// Port of ScaleGestureDetector.java from Android
// * platform/frameworks/base/core/java/android/view/ScaleGestureDetector.java
// * Change-Id: I3e7926a4f6f9ab4951f380bd004499c78b3bda69
// * Please update the Change-Id as upstream Android changes are pulled.
class ScaleGestureDetector {
public:
struct GESTURE_DETECTION_EXPORT Config {
Config();
~Config();
// Distance the current span can deviate from the initial span before
// scaling will start (in dips). The span is the diameter of the circle with
// a radius of average pointer deviation from the focal point.
float span_slop;
// Minimum accepted value for TouchMajor while scaling (in dips).
float min_scaling_touch_major;
// Minimum span needed to initiate a scaling gesture (in dips).
float min_scaling_span;
// Minimum pinch span change before pinch occurs (in dips). See
// crbug.com/373318.
float min_pinch_update_span_delta;
};
class ScaleGestureListener {
public:
virtual ~ScaleGestureListener() {}
virtual bool OnScale(const ScaleGestureDetector& detector,
const MotionEvent& e) = 0;
virtual bool OnScaleBegin(const ScaleGestureDetector& detector,
const MotionEvent& e) = 0;
virtual void OnScaleEnd(const ScaleGestureDetector& detector,
const MotionEvent& e) = 0;
};
// A convenience class to extend when you only want to listen for a subset of
// scaling-related events. This implements all methods in
// |ScaleGestureListener| but does nothing.
// |OnScale()| returns false so that a subclass can retrieve the accumulated
// scale factor in an overridden |OnScaleEnd()|.
// |OnScaleBegin() returns true.
class SimpleScaleGestureListener : public ScaleGestureListener {
public:
// ScaleGestureListener implementation.
virtual bool OnScale(const ScaleGestureDetector&,
const MotionEvent&) OVERRIDE;
virtual bool OnScaleBegin(const ScaleGestureDetector&,
const MotionEvent&) OVERRIDE;
virtual void OnScaleEnd(const ScaleGestureDetector&,
const MotionEvent&) OVERRIDE;
};
ScaleGestureDetector(const Config& config, ScaleGestureListener* listener);
virtual ~ScaleGestureDetector();
// Accepts MotionEvents and dispatches events to a |ScaleGestureListener|
// when appropriate.
//
// Note: Applications should pass a complete and consistent event stream to
// this method. A complete and consistent event stream involves all
// MotionEvents from the initial ACTION_DOWN to the final ACTION_UP or
// ACTION_CANCEL.
//
// Returns true if the event was processed and the detector wants to receive
// the rest of the MotionEvents in this event stream.
bool OnTouchEvent(const MotionEvent& event);
// This method may be called by the owner when a a double-tap event has been
// detected *for the same event stream* being fed to this instance of the
// ScaleGestureDetector. As call order is important here, the double-tap
// detector should always be offered events *before* the ScaleGestureDetector.
bool OnDoubleTap(const MotionEvent& event);
// Set whether the associated |ScaleGestureListener| should receive
// OnScale callbacks when the user performs a doubletap followed by a swipe.
bool IsInProgress() const;
bool InDoubleTapMode() const;
float GetFocusX() const;
float GetFocusY() const;
float GetCurrentSpan() const;
float GetCurrentSpanX() const;
float GetCurrentSpanY() const;
float GetPreviousSpan() const;
float GetPreviousSpanX() const;
float GetPreviousSpanY() const;
float GetScaleFactor() const;
base::TimeDelta GetTimeDelta() const;
base::TimeTicks GetEventTime() const;
private:
enum DoubleTapMode { DOUBLE_TAP_MODE_NONE, DOUBLE_TAP_MODE_IN_PROGRESS };
// The TouchMajor/TouchMinor elements of a MotionEvent can flutter/jitter on
// some hardware/driver combos. Smooth out to get kinder, gentler behavior.
void AddTouchHistory(const MotionEvent& ev);
void ResetTouchHistory();
void ResetScaleWithSpan(float span);
ScaleGestureListener* const listener_;
float focus_x_;
float focus_y_;
float curr_span_;
float prev_span_;
float initial_span_;
float curr_span_x_;
float curr_span_y_;
float prev_span_x_;
float prev_span_y_;
base::TimeTicks curr_time_;
base::TimeTicks prev_time_;
bool in_progress_;
float span_slop_;
float min_span_;
// Bounds for recently seen values.
float touch_upper_;
float touch_lower_;
float touch_history_last_accepted_;
int touch_history_direction_;
base::TimeTicks touch_history_last_accepted_time_;
float touch_min_major_;
float touch_max_major_;
float double_tap_focus_x_;
float double_tap_focus_y_;
DoubleTapMode double_tap_mode_;
bool event_before_or_above_starting_gesture_event_;
DISALLOW_COPY_AND_ASSIGN(ScaleGestureDetector);
};
} // namespace ui
#endif // UI_EVENTS_GESTURE_DETECTION_SCALE_GESTURE_DETECTOR_H_
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