compose/foundation/foundation/integration-tests/foundation-demos/src/main/java/androidx/compose/foundation/demos/relocation/BringIntoViewResponderDemo.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.demos.relocation

import androidx.compose.foundation.ExperimentalFoundationApi
import androidx.compose.foundation.border
import androidx.compose.foundation.focusable
import androidx.compose.foundation.interaction.MutableInteractionSource
import androidx.compose.foundation.interaction.collectIsFocusedAsState
import androidx.compose.foundation.layout.Box
import androidx.compose.foundation.layout.Column
import androidx.compose.foundation.layout.Row
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.size
import androidx.compose.foundation.relocation.BringIntoViewResponder
import androidx.compose.foundation.relocation.bringIntoViewResponder
import androidx.compose.material.Text
import androidx.compose.runtime.Composable
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.geometry.Offset
import androidx.compose.ui.geometry.Rect
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.layout.layout
import androidx.compose.ui.unit.Constraints
import androidx.compose.ui.unit.IntOffset
import androidx.compose.ui.unit.dp
import androidx.compose.ui.unit.round

@OptIn(ExperimentalFoundationApi::class)
@Composable
fun BringIntoViewResponderDemo() {
    Column {
        Text(
            "Each cell in this box is focusable, use the arrow keys/tab/dpad to move focus " +
                "around. The container will always move the focused cell to the top-left corner. " +
                "(Since focusables send a bring into view request whenever they are focused.)"
        )
        var offset: IntOffset by remember { mutableStateOf(IntOffset.Zero) }
        Box(
            modifier = Modifier
                .size(100.dp)
                .layout { measurable, constraints ->
                    // Allow the content to be as big as it wants.
                    val placeable = measurable.measure(
                        constraints.copy(
                            maxWidth = Constraints.Infinity,
                            maxHeight = Constraints.Infinity
                        )
                    )

                    layout(constraints.maxWidth, constraints.maxHeight) {
                        // Place the last-requested rectangle at the top-left of the box.
                        placeable.place(offset)
                    }
                }
                .bringIntoViewResponder(remember {
                    object : BringIntoViewResponder {
                        override fun calculateRectForParent(localRect: Rect): Rect {
                            // Ask our parent to bring our top-left corner into view, since that's
                            // where we're always going to position the requested content.
                            return Rect(Offset.Zero, localRect.size)
                        }

                        @ExperimentalFoundationApi
                        override suspend fun bringChildIntoView(localRect: () -> Rect?) {
                            // Offset the content right and down by the offset of the requested area
                            // so that it will always be aligned to the top-left of the box.
                            localRect()?.also {
                                offset = -it.topLeft.round()
                            }
                        }
                    }
                })
        ) {
            LargeContentWithFocusableChildren()
        }
    }
}

@Composable
private fun LargeContentWithFocusableChildren() {
    Column {
        repeat(10) { row ->
            Row {
                repeat(10) { column ->
                    val interactionSource = remember { MutableInteractionSource() }
                    val isFocused by interactionSource.collectIsFocusedAsState()
                    Text(
                        "$row x $column",
                        Modifier
                            .focusable(interactionSource = interactionSource)
                            .then(
                                if (isFocused) Modifier.border(1.dp, Color.Blue) else Modifier
                            )
                            .padding(8.dp)
                    )
                }
            }
        }
    }
}