commonMain.androidx.compose.material.DragGestureDetectorCopy.kt Maven / Gradle / Ivy

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/*
 * Copyright 2021 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package androidx.compose.material

// Copy-paste version of DragGestureDetector.kt. Please don't change this file without changing
// DragGestureDetector.kt

import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.input.pointer.AwaitPointerEventScope
import androidx.compose.ui.input.pointer.PointerEvent
import androidx.compose.ui.input.pointer.PointerEventPass
import androidx.compose.ui.input.pointer.PointerId
import androidx.compose.ui.input.pointer.PointerInputChange
import androidx.compose.ui.input.pointer.PointerType
import androidx.compose.ui.input.pointer.changedToUpIgnoreConsumed
import androidx.compose.ui.platform.ViewConfiguration
import androidx.compose.ui.unit.dp
import androidx.compose.ui.util.fastFirstOrNull
import kotlin.math.abs
import kotlin.math.sign

internal suspend fun AwaitPointerEventScope.awaitHorizontalPointerSlopOrCancellation(
    pointerId: PointerId,
    pointerType: PointerType,
    onPointerSlopReached: (change: PointerInputChange, overSlop: Float) -> Unit
) = awaitPointerSlopOrCancellation(
    pointerId = pointerId,
    pointerType = pointerType,
    onPointerSlopReached = onPointerSlopReached,
    getDragDirectionValue = { it.x }
)

private suspend inline fun AwaitPointerEventScope.awaitPointerSlopOrCancellation(
    pointerId: PointerId,
    pointerType: PointerType,
    onPointerSlopReached: (PointerInputChange, Float) -> Unit,
    getDragDirectionValue: (Offset) -> Float
): PointerInputChange? {
    if (currentEvent.isPointerUp(pointerId)) {
        return null // The pointer has already been lifted, so the gesture is canceled
    }
    val touchSlop = viewConfiguration.pointerSlop(pointerType)
    var pointer: PointerId = pointerId
    var totalPositionChange = 0f

    while (true) {
        val event = awaitPointerEvent()
        val dragEvent = event.changes.fastFirstOrNull { it.id == pointer }!!
        if (dragEvent.isConsumed) {
            return null
        } else if (dragEvent.changedToUpIgnoreConsumed()) {
            val otherDown = event.changes.fastFirstOrNull { it.pressed }
            if (otherDown == null) {
                // This is the last "up"
                return null
            } else {
                pointer = otherDown.id
            }
        } else {
            val currentPosition = dragEvent.position
            val previousPosition = dragEvent.previousPosition
            val positionChange = getDragDirectionValue(currentPosition) -
                getDragDirectionValue(previousPosition)
            totalPositionChange += positionChange

            val inDirection = abs(totalPositionChange)
            if (inDirection < touchSlop) {
                // verify that nothing else consumed the drag event
                awaitPointerEvent(PointerEventPass.Final)
                if (dragEvent.isConsumed) {
                    return null
                }
            } else {
                onPointerSlopReached(
                    dragEvent,
                    totalPositionChange - (sign(totalPositionChange) * touchSlop)
                )
                if (dragEvent.isConsumed) {
                    return dragEvent
                } else {
                    totalPositionChange = 0f
                }
            }
        }
    }
}

private fun PointerEvent.isPointerUp(pointerId: PointerId): Boolean =
    changes.fastFirstOrNull { it.id == pointerId }?.pressed != true

private val mouseSlop = 0.125.dp
private val defaultTouchSlop = 18.dp // The default touch slop on Android devices
private val mouseToTouchSlopRatio = mouseSlop / defaultTouchSlop

internal fun ViewConfiguration.pointerSlop(pointerType: PointerType): Float {
    return when (pointerType) {
        PointerType.Mouse -> touchSlop * mouseToTouchSlopRatio
        else -> touchSlop
    }
}