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Higher level abstractions of the Compose UI primitives. This library is design system agnostic, providing the high-level building blocks for both application and design-system developers
/*
* 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.foundation.gestures
import androidx.compose.animation.core.AnimationSpec
import androidx.compose.animation.core.AnimationState
import androidx.compose.animation.core.Spring
import androidx.compose.animation.core.SpringSpec
import androidx.compose.animation.core.VectorConverter
import androidx.compose.animation.core.animateTo
import androidx.compose.foundation.MutatePriority
import androidx.compose.foundation.MutatorMutex
import androidx.compose.foundation.internal.JvmDefaultWithCompatibility
import androidx.compose.runtime.Composable
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.rememberUpdatedState
import androidx.compose.ui.geometry.Offset
import kotlinx.coroutines.coroutineScope
/**
* State of [transformable]. Allows for a granular control of how different gesture
* transformations are consumed by the user as well as to write custom transformation methods
* using [transform] suspend function.
*/
@JvmDefaultWithCompatibility
interface TransformableState {
/**
* Call this function to take control of transformations and gain the ability to send transform
* events via [TransformScope.transformBy]. All actions that change zoom, pan or rotation
* values must be performed within a [transform] block (even if they don't call any other
* methods on this object) in order to guarantee that mutual exclusion is enforced.
*
* If [transform] is called from elsewhere with the [transformPriority] higher or equal to
* ongoing transform, ongoing transform will be canceled.
*/
suspend fun transform(
transformPriority: MutatePriority = MutatePriority.Default,
block: suspend TransformScope.() -> Unit
)
/**
* Whether this [TransformableState] is currently transforming by gesture or programmatically or
* not.
*/
val isTransformInProgress: Boolean
}
/**
* Scope used for suspending transformation operations
*/
@JvmDefaultWithCompatibility
interface TransformScope {
/**
* Attempts to transform by [zoomChange] in relative multiplied value, by [panChange] in
* pixels and by [rotationChange] in degrees.
*
* @param zoomChange scale factor multiplier change for zoom
* @param panChange panning offset change, in [Offset] pixels
* @param rotationChange change of the rotation in degrees
*/
fun transformBy(
zoomChange: Float = 1f,
panChange: Offset = Offset.Zero,
rotationChange: Float = 0f
)
}
/**
* Default implementation of [TransformableState] interface that contains necessary information
* about the ongoing transformations and provides smooth transformation capabilities.
*
* This is the simplest way to set up a [transformable] modifier. When constructing this
* [TransformableState], you must provide a [onTransformation] lambda, which will be invoked
* whenever pan, zoom or rotation happens (by gesture input or any [TransformableState.transform]
* call) with the deltas from the previous event.
*
* @param onTransformation callback invoked when transformation occurs. The callback receives the
* change from the previous event. It's relative scale multiplier for zoom, [Offset] in pixels
* for pan and degrees for rotation. Callers should update their state in this lambda.
*/
fun TransformableState(
onTransformation: (zoomChange: Float, panChange: Offset, rotationChange: Float) -> Unit
): TransformableState = DefaultTransformableState(onTransformation)
/**
* Create and remember default implementation of [TransformableState] interface that contains
* necessary information about the ongoing transformations and provides smooth transformation
* capabilities.
*
* This is the simplest way to set up a [transformable] modifier. When constructing this
* [TransformableState], you must provide a [onTransformation] lambda, which will be invoked
* whenever pan, zoom or rotation happens (by gesture input or any [TransformableState.transform]
* call) with the deltas from the previous event.
*
* @param onTransformation callback invoked when transformation occurs. The callback receives the
* change from the previous event. It's relative scale multiplier for zoom, [Offset] in pixels
* for pan and degrees for rotation. Callers should update their state in this lambda.
*/
@Composable
fun rememberTransformableState(
onTransformation: (zoomChange: Float, panChange: Offset, rotationChange: Float) -> Unit
): TransformableState {
val lambdaState = rememberUpdatedState(onTransformation)
return remember { TransformableState { z, p, r -> lambdaState.value.invoke(z, p, r) } }
}
/**
* Animate zoom by a ratio of [zoomFactor] over the current size and suspend until its finished.
*
* @param zoomFactor ratio over the current size by which to zoom. For example, if [zoomFactor]
* is `3f`, zoom will be increased 3 fold from the current value.
* @param animationSpec [AnimationSpec] to be used for animation
*/
suspend fun TransformableState.animateZoomBy(
zoomFactor: Float,
animationSpec: AnimationSpec = SpringSpec(stiffness = Spring.StiffnessLow)
) {
require(zoomFactor > 0) {
"zoom value should be greater than 0"
}
var previous = 1f
transform {
AnimationState(initialValue = previous).animateTo(zoomFactor, animationSpec) {
val scaleFactor = if (previous == 0f) 1f else this.value / previous
transformBy(zoomChange = scaleFactor)
previous = this.value
}
}
}
/**
* Animate rotate by a ratio of [degrees] clockwise and suspend until its finished.
*
* @param degrees ratio over the current size by which to rotate, in degrees
* @param animationSpec [AnimationSpec] to be used for animation
*/
suspend fun TransformableState.animateRotateBy(
degrees: Float,
animationSpec: AnimationSpec = SpringSpec(stiffness = Spring.StiffnessLow)
) {
var previous = 0f
transform {
AnimationState(initialValue = previous).animateTo(degrees, animationSpec) {
val delta = this.value - previous
transformBy(rotationChange = delta)
previous = this.value
}
}
}
/**
* Animate pan by [offset] Offset in pixels and suspend until its finished
*
* @param offset offset to pan, in pixels
* @param animationSpec [AnimationSpec] to be used for pan animation
*/
suspend fun TransformableState.animatePanBy(
offset: Offset,
animationSpec: AnimationSpec = SpringSpec(stiffness = Spring.StiffnessLow)
) {
var previous = Offset.Zero
transform {
AnimationState(
typeConverter = Offset.VectorConverter,
initialValue = previous
)
.animateTo(offset, animationSpec) {
val delta = this.value - previous
transformBy(panChange = delta)
previous = this.value
}
}
}
/**
* Zoom without animation by a ratio of [zoomFactor] over the current size and suspend until it's
* set.
*
* @param zoomFactor ratio over the current size by which to zoom
*/
suspend fun TransformableState.zoomBy(zoomFactor: Float) = transform {
transformBy(zoomFactor, Offset.Zero, 0f)
}
/**
* Rotate without animation by a [degrees] degrees and suspend until it's set.
*
* @param degrees degrees by which to rotate
*/
suspend fun TransformableState.rotateBy(degrees: Float) = transform {
transformBy(1f, Offset.Zero, degrees)
}
/**
* Pan without animation by a [offset] Offset in pixels and suspend until it's set.
*
* @param offset offset in pixels by which to pan
*/
suspend fun TransformableState.panBy(offset: Offset) = transform {
transformBy(1f, offset, 0f)
}
/**
* Stop and suspend until any ongoing [TransformableState.transform] with priority
* [terminationPriority] or lower is terminated.
*
* @param terminationPriority transformation that runs with this priority or lower will be stopped
*/
suspend fun TransformableState.stopTransformation(
terminationPriority: MutatePriority = MutatePriority.Default
) {
this.transform(terminationPriority) {
// do nothing, just lock the mutex so other scroll actors are cancelled
}
}
private class DefaultTransformableState(
val onTransformation: (zoomChange: Float, panChange: Offset, rotationChange: Float) -> Unit
) : TransformableState {
private val transformScope: TransformScope = object : TransformScope {
override fun transformBy(zoomChange: Float, panChange: Offset, rotationChange: Float) =
onTransformation(zoomChange, panChange, rotationChange)
}
private val transformMutex = MutatorMutex()
private val isTransformingState = mutableStateOf(false)
override suspend fun transform(
transformPriority: MutatePriority,
block: suspend TransformScope.() -> Unit
): Unit = coroutineScope {
transformMutex.mutateWith(transformScope, transformPriority) {
isTransformingState.value = true
try {
block()
} finally {
isTransformingState.value = false
}
}
}
override val isTransformInProgress: Boolean
get() = isTransformingState.value
}