1 /*
<lambda>null2  * Copyright (C) 2022 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 androidx.constraintlayout.compose
18 
19 import androidx.compose.runtime.MutableFloatState
20 import androidx.compose.runtime.withFrameNanos
21 import androidx.compose.ui.geometry.Offset
22 import androidx.compose.ui.unit.Velocity
23 
24 /**
25  * Helper class that handles the interactions between Compose and
26  * [androidx.constraintlayout.core.state.Transition].
27  */
28 @ExperimentalMotionApi
29 internal class TransitionHandler(
30     private val motionMeasurer: MotionMeasurer,
31     private val motionProgress: MutableFloatState
32 ) {
33     private val transition: androidx.constraintlayout.core.state.Transition
34         get() = motionMeasurer.transition
35 
36     /**
37      * Whether we consume the rest of the drag for OnSwipe.
38      *
39      * @see androidx.constraintlayout.core.state.Transition.isFirstDownAccepted
40      */
41     fun onAcceptFirstDownForOnSwipe(offset: Offset) =
42         transition.isFirstDownAccepted(offset.x, offset.y)
43 
44     /** The [motionProgress] is updated based on the [Offset] from a single drag event. */
45     fun updateProgressOnDrag(dragAmount: Offset) {
46         val progressDelta =
47             transition.dragToProgress(
48                 motionProgress.floatValue,
49                 motionMeasurer.layoutCurrentWidth,
50                 motionMeasurer.layoutCurrentHeight,
51                 dragAmount.x,
52                 dragAmount.y
53             )
54         var newProgress = motionProgress.floatValue + progressDelta
55         newProgress = newProgress.coerceIn(0f, 1f)
56         motionProgress.floatValue = newProgress
57     }
58 
59     /**
60      * Called when a swipe event ends, sets up the underlying Transition with the [velocity] of the
61      * swipe at the next frame.
62      */
63     suspend fun onTouchUp(velocity: Velocity) {
64         withFrameNanos { timeNanos ->
65             transition.setTouchUp(motionProgress.floatValue, timeNanos, velocity.x, velocity.y)
66         }
67     }
68 
69     /**
70      * Call to update the [motionProgress] after a swipe has ended and as long as there are no other
71      * touch gestures.
72      */
73     suspend fun updateProgressWhileTouchUp() {
74         val newProgress = withFrameNanos { timeNanos -> transition.getTouchUpProgress(timeNanos) }
75         motionProgress.floatValue = newProgress
76     }
77 
78     /**
79      * Returns true if the progress is still expected to be updated by [updateProgressWhileTouchUp].
80      */
81     fun pendingProgressWhileTouchUp(): Boolean {
82         return transition.isTouchNotDone(motionProgress.floatValue)
83     }
84 }
85