commonMain.androidx.compose.ui.focus.FocusEventModifierNode.kt Maven / Gradle / Ivy

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Compose UI primitives. This library contains the primitives that form the Compose UI Toolkit, such as drawing, measurement and layout.

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/*
 * 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.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.requireOwner
import androidx.compose.ui.node.visitSelfAndAncestors
import androidx.compose.ui.node.visitSelfAndChildren

/**
 * Implement this interface create a modifier node that can be used to observe focus state changes
 * to a [FocusTargetNode] down the hierarchy.
 */
interface FocusEventModifierNode : DelegatableNode {

    /**
     * A parent FocusEventNode is notified of [FocusState] changes to the [FocusTargetNode]
     * associated with this [FocusEventModifierNode].
     */
    fun onFocusEvent(focusState: FocusState)
}

internal fun FocusEventModifierNode.invalidateFocusEvent() {
    requireOwner().focusOwner.scheduleInvalidation(this)
}

internal fun FocusEventModifierNode.getFocusState(): FocusState {
    visitSelfAndChildren(Nodes.FocusTarget) {
        when (val focusState = it.focusState) {
            // 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@visitSelfAndChildren
        }
    }
    return Inactive
}

/**
 * Sends a "Focus Event" up the hierarchy that asks all [FocusEventModifierNode]s to recompute their
 * observed focus state.
 *
 * Make this public after [FocusTargetNode] is made public.
 */
internal fun FocusTargetNode.refreshFocusEventNodes() {
    visitSelfAndAncestors(Nodes.FocusEvent, untilType = Nodes.FocusTarget) {
        // TODO(251833873): Consider caching it.getFocusState().
        it.onFocusEvent(it.getFocusState())
    }
}