1 /*
2  * Copyright (C) 2024 The Android Open Source Project
3  *
4  * Licensed under the Apache License, Version 2.0 (the "License");
5  * you may not use this file except in compliance with the License.
6  * You may obtain a copy of the License at
7  *
8  *      http://www.apache.org/licenses/LICENSE-2.0
9  *
10  * Unless required by applicable law or agreed to in writing, software
11  * distributed under the License is distributed on an "AS IS" BASIS,
12  * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13  * See the License for the specific language governing permissions and
14  * limitations under the License.
15  */
16 
17 package com.android.systemui.touchpad.tutorial.ui.gesture
18 
19 import android.view.MotionEvent
20 import androidx.compose.ui.input.pointer.util.VelocityTracker1D
21 import java.util.function.Consumer
22 
23 /** Velocity in pixels/ms. */
24 @JvmInline value class Velocity(val value: Float)
25 
26 /**
27  * Tracks velocity for processed MotionEvents. Useful for recognizing gestures based on velocity.
28  */
29 interface VelocityTracker : Consumer<MotionEvent> {
30 
calculateVelocitynull31     fun calculateVelocity(): Velocity
32 }
33 
34 class VerticalVelocityTracker(
35     private val velocityTracker: VelocityTracker1D = VelocityTracker1D(isDataDifferential = false)
36 ) : VelocityTracker {
37 
38     override fun accept(event: MotionEvent) {
39         val action = event.actionMasked
40         if (action == MotionEvent.ACTION_DOWN) {
41             velocityTracker.resetTracking()
42         }
43         velocityTracker.addDataPoint(event.eventTime, event.y)
44     }
45 
46     /**
47      * Calculates velocity on demand - this calculation can be expensive so shouldn't be called
48      * after every event.
49      */
50     override fun calculateVelocity() = Velocity(velocityTracker.calculateVelocity() / 1000)
51 }
52