Hoverable.kt
/*
* 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
import androidx.compose.foundation.interaction.HoverInteraction
import androidx.compose.foundation.interaction.MutableInteractionSource
import androidx.compose.ui.Modifier
import androidx.compose.ui.input.pointer.PointerEvent
import androidx.compose.ui.input.pointer.PointerEventPass
import androidx.compose.ui.input.pointer.PointerEventType
import androidx.compose.ui.node.ModifierNodeElement
import androidx.compose.ui.node.PointerInputModifierNode
import androidx.compose.ui.platform.InspectorInfo
import androidx.compose.ui.unit.IntSize
import kotlinx.coroutines.launch
/**
* Configure component to be hoverable via pointer enter/exit events.
*
* @sample androidx.compose.foundation.samples.HoverableSample
*
* @param interactionSource [MutableInteractionSource] that will be used to emit
* [HoverInteraction.Enter] when this element is being hovered.
* @param enabled Controls the enabled state. When `false`, hover events will be ignored.
*/
fun Modifier.hoverable(
interactionSource: MutableInteractionSource,
enabled: Boolean = true
) = this then if (enabled) HoverableElement(interactionSource) else Modifier
private class HoverableElement(
private val interactionSource: MutableInteractionSource
) : ModifierNodeElement<HoverableNode>() {
override fun create() = HoverableNode(interactionSource)
override fun update(node: HoverableNode) {
node.updateInteractionSource(interactionSource)
}
override fun hashCode(): Int {
return 31 * interactionSource.hashCode()
}
override fun equals(other: Any?): Boolean {
if (this === other) return true
if (other !is HoverableElement) return false
if (other.interactionSource != interactionSource) return false
return true
}
override fun InspectorInfo.inspectableProperties() {
name = "hoverable"
properties["interactionSource"] = interactionSource
}
}
private class HoverableNode(
private var interactionSource: MutableInteractionSource
) : PointerInputModifierNode, Modifier.Node() {
private var hoverInteraction: HoverInteraction.Enter? = null
fun updateInteractionSource(interactionSource: MutableInteractionSource) {
if (this.interactionSource != interactionSource) {
tryEmitExit()
// b/273699888 TODO: Define behavior if there is an ongoing hover
this.interactionSource = interactionSource
}
}
override fun onPointerEvent(
pointerEvent: PointerEvent,
pass: PointerEventPass,
bounds: IntSize
) {
if (pass == PointerEventPass.Main) {
when (pointerEvent.type) {
PointerEventType.Enter -> coroutineScope.launch { emitEnter() }
PointerEventType.Exit -> coroutineScope.launch { emitExit() }
}
}
}
override fun onCancelPointerInput() {
tryEmitExit()
}
override fun onDetach() {
tryEmitExit()
}
suspend fun emitEnter() {
if (hoverInteraction == null) {
val interaction = HoverInteraction.Enter()
interactionSource.emit(interaction)
hoverInteraction = interaction
}
}
suspend fun emitExit() {
hoverInteraction?.let { oldValue ->
val interaction = HoverInteraction.Exit(oldValue)
interactionSource.emit(interaction)
hoverInteraction = null
}
}
fun tryEmitExit() {
hoverInteraction?.let { oldValue ->
val interaction = HoverInteraction.Exit(oldValue)
interactionSource.tryEmit(interaction)
hoverInteraction = null
}
}
}