FocusEventModifierNode.kt
/*
* Copyright 2020 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.ui.focus
import androidx.compose.ui.ExperimentalComposeUiApi
import androidx.compose.ui.focus.FocusStateImpl.Active
import androidx.compose.ui.focus.FocusStateImpl.ActiveParent
import androidx.compose.ui.focus.FocusStateImpl.Captured
import androidx.compose.ui.focus.FocusStateImpl.Inactive
import androidx.compose.ui.node.DelegatableNode
import androidx.compose.ui.node.Nodes
import androidx.compose.ui.node.visitAncestors
import androidx.compose.ui.node.visitChildren
/**
* Implement this interface create a modifier node that can be used to observe focus state changes
* to a [FocusTargetModifierNode] down the hierarchy.
*/
@ExperimentalComposeUiApi
interface FocusEventModifierNode : DelegatableNode {
/**
* A parent FocusEventNode is notified of [FocusState] changes to the [FocusTargetModifierNode]
* associated with this [FocusEventModifierNode].
*/
fun onFocusEvent(focusState: FocusState)
}
@OptIn(ExperimentalComposeUiApi::class)
internal fun FocusEventModifierNode.getFocusState(): FocusState {
visitChildren(Nodes.FocusTarget) {
when (val focusState = it.focusStateImpl) {
// If we find a focused child, we use that child's state as the aggregated state.
Active, ActiveParent, Captured -> return focusState
// We use the Inactive state only if we don't have a focused child.
// ie. we ignore this child if another child provides aggregated state.
Inactive -> return@visitChildren
}
}
return Inactive
}
/**
* Sends a "Focus Event" up the hierarchy that asks all [FocusEventModifierNode]s to recompute their
* observed focus state.
*
* Make this public after [FocusTargetModifierNode] is made public.
*/
@ExperimentalComposeUiApi
internal fun FocusTargetModifierNode.refreshFocusEventNodes() {
visitAncestors(Nodes.FocusEvent or Nodes.FocusTarget) {
// If we reach the previous focus target node, we have gone too far, as
// this is applies to the another focus event.
if (it.isKind(Nodes.FocusTarget)) return
// TODO(251833873): Consider caching it.getFocusState().
check(it is FocusEventModifierNode)
it.onFocusEvent(it.getFocusState())
}
}