SelectionContainer.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.text.selection

import androidx.compose.foundation.Interaction
import androidx.compose.runtime.Composable
import androidx.compose.runtime.DisposableEffect
import androidx.compose.runtime.Providers
import androidx.compose.runtime.getValue
import androidx.compose.runtime.mutableStateOf
import androidx.compose.runtime.remember
import androidx.compose.runtime.setValue
import androidx.compose.ui.Modifier
import androidx.compose.ui.gesture.dragGestureFilter
import androidx.compose.ui.platform.LocalClipboardManager
import androidx.compose.ui.platform.LocalHapticFeedback
import androidx.compose.ui.platform.LocalTextToolbar
import androidx.compose.ui.text.InternalTextApi

/**
 * Enables text selection for it's direct or indirection children.
 *
 * @sample androidx.compose.foundation.samples.SelectionSample
 */
@OptIn(InternalTextApi::class)
@Composable
fun SelectionContainer(modifier: Modifier = Modifier, content: @Composable () -> Unit) {
    var selection by remember { mutableStateOf<Selection?>(null) }
    SelectionContainer(
        modifier = modifier,
        selection = selection,
        onSelectionChange = {
            selection = it
        },
        children = content
    )
}

/**
 * Disables text selection for it's direct or indirection children. To use this, simply add this
 * to wrap one or more text composables.
 *
 * @sample androidx.compose.foundation.samples.DisableSelectionSample
 */
@Composable
fun DisableSelection(content: @Composable () -> Unit) {
    Providers(
        LocalSelectionRegistrar provides null,
        content = content
    )
}

/**
 * Selection Composable.
 *
 * The selection composable wraps composables and let them to be selectable. It paints the selection
 * area with start and end handles.
 *
 * @suppress
 */
@Suppress("ComposableLambdaParameterNaming", "DEPRECATION")
@InternalTextApi // Used by foundation
@Composable
internal fun SelectionContainer(
    /** A [Modifier] for SelectionContainer. */
    modifier: Modifier = Modifier,
    /** Current Selection status.*/
    selection: Selection?,
    /** A function containing customized behaviour when selection changes. */
    onSelectionChange: (Selection?) -> Unit,
    children: @Composable () -> Unit
) {
    val registrarImpl = remember { SelectionRegistrarImpl() }
    val manager = remember { SelectionManager(registrarImpl) }

    manager.hapticFeedBack = LocalHapticFeedback.current
    manager.clipboardManager = LocalClipboardManager.current
    manager.textToolbar = LocalTextToolbar.current
    manager.onSelectionChange = onSelectionChange
    manager.selection = selection

    Providers(LocalSelectionRegistrar provides registrarImpl) {
        // Get the layout coordinates of the selection container. This is for hit test of
        // cross-composable selection.
        SimpleLayout(modifier = modifier.then(manager.modifier)) {
            children()
            if (manager.interactionState.contains(Interaction.Focused)) {
                manager.selection?.let {
                    for (isStartHandle in listOf(true, false)) {
                        SelectionHandle(
                            startHandlePosition = manager.startHandlePosition,
                            endHandlePosition = manager.endHandlePosition,
                            isStartHandle = isStartHandle,
                            directions = Pair(it.start.direction, it.end.direction),
                            handlesCrossed = it.handlesCrossed,
                            modifier = Modifier.dragGestureFilter(
                                manager.handleDragObserver(
                                    isStartHandle
                                )
                            ),
                            handle = null
                        )
                    }
                }
            }
        }
    }

    DisposableEffect(manager) {
        onDispose {
            manager.hideSelectionToolbar()
        }
    }
}