Checkbox.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.material3

import androidx.compose.animation.animateColorAsState
import androidx.compose.animation.core.animateFloat
import androidx.compose.animation.core.snap
import androidx.compose.animation.core.spring
import androidx.compose.animation.core.tween
import androidx.compose.animation.core.updateTransition
import androidx.compose.foundation.Canvas
import androidx.compose.foundation.interaction.Interaction
import androidx.compose.foundation.interaction.MutableInteractionSource
import androidx.compose.foundation.layout.padding
import androidx.compose.foundation.layout.requiredSize
import androidx.compose.foundation.layout.wrapContentSize
import androidx.compose.foundation.selection.triStateToggleable
import androidx.compose.material.ripple.rememberRipple
import androidx.compose.material3.tokens.CheckboxTokens
import androidx.compose.runtime.Composable
import androidx.compose.runtime.Immutable
import androidx.compose.runtime.Stable
import androidx.compose.runtime.State
import androidx.compose.runtime.remember
import androidx.compose.runtime.rememberUpdatedState
import androidx.compose.ui.Alignment
import androidx.compose.ui.Modifier
import androidx.compose.ui.geometry.CornerRadius
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.geometry.Size
import androidx.compose.ui.graphics.Color
import androidx.compose.ui.graphics.Path
import androidx.compose.ui.graphics.PathMeasure
import androidx.compose.ui.graphics.StrokeCap
import androidx.compose.ui.graphics.drawscope.DrawScope
import androidx.compose.ui.graphics.drawscope.Fill
import androidx.compose.ui.graphics.drawscope.Stroke
import androidx.compose.ui.semantics.Role
import androidx.compose.ui.state.ToggleableState
import androidx.compose.ui.unit.dp
import androidx.compose.ui.util.lerp
import kotlin.math.floor
import kotlin.math.max

/**
 * Material Design checkbox.
 *
 * Checkboxes allow users to select one or more items from a set. Checkboxes can turn an option on
 * or off.
 *
 * ![Checkbox image](https://developer.android.com/images/reference/androidx/compose/material3/checkbox.png)
 *
 * @sample androidx.compose.material3.samples.CheckboxSample
 *
 * @see [TriStateCheckbox] if you require support for an indeterminate state.
 *
 * @param checked whether this checkbox is checked or unchecked
 * @param onCheckedChange called when this checkbox is clicked. If `null`, then this checkbox will
 * not be interactable, unless something else handles its input events and updates its state.
 * @param modifier the [Modifier] to be applied to this checkbox
 * @param enabled controls the enabled state of this checkbox. When `false`, this component will not
 * respond to user input, and it will appear visually disabled and disabled to accessibility
 * services.
 * @param interactionSource the [MutableInteractionSource] representing the stream of [Interaction]s
 * for this checkbox. You can create and pass in your own `remember`ed instance to observe
 * [Interaction]s and customize the appearance / behavior of this checkbox in different states.
 * @param colors [CheckboxColors] that will be used to resolve the colors used for this checkbox in
 * different states. See [CheckboxDefaults.colors].
 */
@Composable
fun Checkbox(
    checked: Boolean,
    onCheckedChange: ((Boolean) -> Unit)?,
    modifier: Modifier = Modifier,
    enabled: Boolean = true,
    interactionSource: MutableInteractionSource = remember { MutableInteractionSource() },
    colors: CheckboxColors = CheckboxDefaults.colors()
) {
    TriStateCheckbox(
        state = ToggleableState(checked),
        onClick = if (onCheckedChange != null) {
            { onCheckedChange(!checked) }
        } else null,
        interactionSource = interactionSource,
        enabled = enabled,
        colors = colors,
        modifier = modifier
    )
}

/**
 * Material Design checkbox parent.
 *
 * Checkboxes can have a parent-child relationship with other checkboxes. When the parent checkbox
 * is checked, all child checkboxes are checked. If a parent checkbox is unchecked, all child
 * checkboxes are unchecked. If some, but not all, child checkboxes are checked, the parent checkbox
 * becomes an indeterminate checkbox.
 *
 * ![Checkbox image](https://developer.android.com/images/reference/androidx/compose/material3/indeterminate-checkbox.png)
 *
 * @sample androidx.compose.material3.samples.TriStateCheckboxSample
 *
 * @see [Checkbox] if you want a simple component that represents Boolean state
 *
 * @param state whether this checkbox is checked, unchecked, or in an indeterminate state
 * @param onClick called when this checkbox is clicked. If `null`, then this checkbox will not be
 * interactable, unless something else handles its input events and updates its [state].
 * @param modifier the [Modifier] to be applied to this checkbox
 * @param enabled controls the enabled state of this checkbox. When `false`, this component will not
 * respond to user input, and it will appear visually disabled and disabled to accessibility
 * services.
 * @param interactionSource the [MutableInteractionSource] representing the stream of [Interaction]s
 * for this checkbox. You can create and pass in your own `remember`ed instance to observe
 * [Interaction]s and customize the appearance / behavior of this checkbox in different states.
 * @param colors [CheckboxColors] that will be used to resolve the colors used for this checkbox in
 * different states. See [CheckboxDefaults.colors].
 */
@Composable
fun TriStateCheckbox(
    state: ToggleableState,
    onClick: (() -> Unit)?,
    modifier: Modifier = Modifier,
    enabled: Boolean = true,
    interactionSource: MutableInteractionSource = remember { MutableInteractionSource() },
    colors: CheckboxColors = CheckboxDefaults.colors()
) {
    val toggleableModifier =
        if (onClick != null) {
            Modifier.triStateToggleable(
                state = state,
                onClick = onClick,
                enabled = enabled,
                role = Role.Checkbox,
                interactionSource = interactionSource,
                indication = rememberRipple(
                    bounded = false,
                    radius = CheckboxTokens.StateLayerSize / 2
                )
            )
        } else {
            Modifier
        }
    CheckboxImpl(
        enabled = enabled,
        value = state,
        modifier = modifier
            .then(
                if (onClick != null) {
                    Modifier.minimumTouchTargetSize()
                } else {
                    Modifier
                }
            )
            .then(toggleableModifier)
            .padding(CheckboxDefaultPadding),
        colors = colors
    )
}

/**
 * Represents the colors used by the three different sections (checkmark, box, and border) of a
 * [Checkbox] or [TriStateCheckbox] in different states.
 *
 * See [CheckboxDefaults.colors] for the default implementation that follows Material
 * specifications.
 */
@Stable
interface CheckboxColors {

    /**
     * Represents the color used for the checkmark inside the checkbox, depending on [state].
     *
     * @param state the [ToggleableState] of the checkbox
     */
    @Composable
    fun checkmarkColor(state: ToggleableState): State<Color>

    /**
     * Represents the color used for the box (background) of the checkbox, depending on [enabled]
     * and [state].
     *
     * @param enabled whether the checkbox is enabled or not
     * @param state the [ToggleableState] of the checkbox
     */
    @Composable
    fun boxColor(enabled: Boolean, state: ToggleableState): State<Color>

    /**
     * Represents the color used for the border of the checkbox, depending on [enabled] and [state].
     *
     * @param enabled whether the checkbox is enabled or not
     * @param state the [ToggleableState] of the checkbox
     */
    @Composable
    fun borderColor(enabled: Boolean, state: ToggleableState): State<Color>
}

/**
 * Defaults used in [Checkbox] and [TriStateCheckbox].
 */
object CheckboxDefaults {
    /**
     * Creates a [CheckboxColors] that will animate between the provided colors according to the
     * Material specification.
     *
     * @param checkedColor the color that will be used for the border and box when checked
     * @param uncheckedColor color that will be used for the border when unchecked
     * @param checkmarkColor color that will be used for the checkmark when checked
     * @param disabledCheckedColor color that will be used for the box and border when disabled and
     * checked
     * @param disabledUncheckedColor color that will be used for the box and border when disabled
     * and not checked
     * @param disabledIndeterminateColor color that will be used for the box and
     * border in a [TriStateCheckbox] when disabled AND in an [ToggleableState.Indeterminate] state.
     */
    @Composable
    fun colors(
        checkedColor: Color =
            MaterialTheme.colorScheme.fromToken(CheckboxTokens.SelectedContainerColor),
        uncheckedColor: Color =
            MaterialTheme.colorScheme.fromToken(CheckboxTokens.UnselectedOutlineColor),
        checkmarkColor: Color =
            MaterialTheme.colorScheme.fromToken(CheckboxTokens.SelectedIconColor),
        disabledCheckedColor: Color =
            MaterialTheme.colorScheme
                .fromToken(CheckboxTokens.SelectedDisabledContainerColor)
                .copy(alpha = CheckboxTokens.SelectedDisabledContainerOpacity),
        disabledUncheckedColor: Color =
            MaterialTheme.colorScheme
                .fromToken(CheckboxTokens.UnselectedDisabledOutlineColor)
                .copy(alpha = CheckboxTokens.UnselectedDisabledContainerOpacity),
        disabledIndeterminateColor: Color = disabledCheckedColor
    ): CheckboxColors {
        return remember(
            checkedColor,
            uncheckedColor,
            checkmarkColor,
            disabledCheckedColor,
            disabledUncheckedColor,
            disabledIndeterminateColor,
        ) {
            DefaultCheckboxColors(
                checkedBorderColor = checkedColor,
                checkedBoxColor = checkedColor,
                checkedCheckmarkColor = checkmarkColor,
                uncheckedCheckmarkColor = checkmarkColor.copy(alpha = 0f),
                uncheckedBoxColor = checkedColor.copy(alpha = 0f),
                disabledCheckedBoxColor = disabledCheckedColor,
                disabledUncheckedBoxColor = disabledUncheckedColor.copy(alpha = 0f),
                disabledIndeterminateBoxColor = disabledIndeterminateColor,
                uncheckedBorderColor = uncheckedColor,
                disabledBorderColor = disabledCheckedColor,
                disabledIndeterminateBorderColor = disabledIndeterminateColor,
            )
        }
    }
}

@Composable
private fun CheckboxImpl(
    enabled: Boolean,
    value: ToggleableState,
    modifier: Modifier,
    colors: CheckboxColors
) {
    val transition = updateTransition(value)
    val checkDrawFraction = transition.animateFloat(
        transitionSpec = {
            when {
                initialState == ToggleableState.Off -> tween(CheckAnimationDuration)
                targetState == ToggleableState.Off -> snap(BoxOutDuration)
                else -> spring()
            }
        }
    ) {
        when (it) {
            ToggleableState.On -> 1f
            ToggleableState.Off -> 0f
            ToggleableState.Indeterminate -> 1f
        }
    }

    val checkCenterGravitationShiftFraction = transition.animateFloat(
        transitionSpec = {
            when {
                initialState == ToggleableState.Off -> snap()
                targetState == ToggleableState.Off -> snap(BoxOutDuration)
                else -> tween(durationMillis = CheckAnimationDuration)
            }
        }
    ) {
        when (it) {
            ToggleableState.On -> 0f
            ToggleableState.Off -> 0f
            ToggleableState.Indeterminate -> 1f
        }
    }
    val checkCache = remember { CheckDrawingCache() }
    val checkColor = colors.checkmarkColor(value)
    val boxColor = colors.boxColor(enabled, value)
    val borderColor = colors.borderColor(enabled, value)
    Canvas(modifier.wrapContentSize(Alignment.Center).requiredSize(CheckboxSize)) {
        val strokeWidthPx = floor(StrokeWidth.toPx())
        drawBox(
            boxColor = boxColor.value,
            borderColor = borderColor.value,
            radius = RadiusSize.toPx(),
            strokeWidth = strokeWidthPx
        )
        drawCheck(
            checkColor = checkColor.value,
            checkFraction = checkDrawFraction.value,
            crossCenterGravitation = checkCenterGravitationShiftFraction.value,
            strokeWidthPx = strokeWidthPx,
            drawingCache = checkCache
        )
    }
}

private fun DrawScope.drawBox(
    boxColor: Color,
    borderColor: Color,
    radius: Float,
    strokeWidth: Float
) {
    val halfStrokeWidth = strokeWidth / 2.0f
    val stroke = Stroke(strokeWidth)
    val checkboxSize = size.width
    if (boxColor == borderColor) {
        drawRoundRect(
            boxColor,
            size = Size(checkboxSize, checkboxSize),
            cornerRadius = CornerRadius(radius),
            style = Fill
        )
    } else {
        drawRoundRect(
            boxColor,
            topLeft = Offset(strokeWidth, strokeWidth),
            size = Size(checkboxSize - strokeWidth * 2, checkboxSize - strokeWidth * 2),
            cornerRadius = CornerRadius(max(0f, radius - strokeWidth)),
            style = Fill
        )
        drawRoundRect(
            borderColor,
            topLeft = Offset(halfStrokeWidth, halfStrokeWidth),
            size = Size(checkboxSize - strokeWidth, checkboxSize - strokeWidth),
            cornerRadius = CornerRadius(radius - halfStrokeWidth),
            style = stroke
        )
    }
}

private fun DrawScope.drawCheck(
    checkColor: Color,
    checkFraction: Float,
    crossCenterGravitation: Float,
    strokeWidthPx: Float,
    drawingCache: CheckDrawingCache
) {
    val stroke = Stroke(width = strokeWidthPx, cap = StrokeCap.Square)
    val width = size.width
    val checkCrossX = 0.4f
    val checkCrossY = 0.7f
    val leftX = 0.2f
    val leftY = 0.5f
    val rightX = 0.8f
    val rightY = 0.3f

    val gravitatedCrossX = lerp(checkCrossX, 0.5f, crossCenterGravitation)
    val gravitatedCrossY = lerp(checkCrossY, 0.5f, crossCenterGravitation)
    // gravitate only Y for end to achieve center line
    val gravitatedLeftY = lerp(leftY, 0.5f, crossCenterGravitation)
    val gravitatedRightY = lerp(rightY, 0.5f, crossCenterGravitation)

    with(drawingCache) {
        checkPath.reset()
        checkPath.moveTo(width * leftX, width * gravitatedLeftY)
        checkPath.lineTo(width * gravitatedCrossX, width * gravitatedCrossY)
        checkPath.lineTo(width * rightX, width * gravitatedRightY)
        // TODO: replace with proper declarative non-android alternative when ready (b/158188351)
        pathMeasure.setPath(checkPath, false)
        pathToDraw.reset()
        pathMeasure.getSegment(
            0f, pathMeasure.length * checkFraction, pathToDraw, true
        )
    }
    drawPath(drawingCache.pathToDraw, checkColor, style = stroke)
}

@Immutable
private class CheckDrawingCache(
    val checkPath: Path = Path(),
    val pathMeasure: PathMeasure = PathMeasure(),
    val pathToDraw: Path = Path()
)

/**
 * Default [CheckboxColors] implementation.
 */
@Immutable
private class DefaultCheckboxColors(
    private val checkedCheckmarkColor: Color,
    private val uncheckedCheckmarkColor: Color,
    private val checkedBoxColor: Color,
    private val uncheckedBoxColor: Color,
    private val disabledCheckedBoxColor: Color,
    private val disabledUncheckedBoxColor: Color,
    private val disabledIndeterminateBoxColor: Color,
    private val checkedBorderColor: Color,
    private val uncheckedBorderColor: Color,
    private val disabledBorderColor: Color,
    private val disabledIndeterminateBorderColor: Color
) : CheckboxColors {
    @Composable
    override fun checkmarkColor(state: ToggleableState): State<Color> {
        val target = if (state == ToggleableState.Off) {
            uncheckedCheckmarkColor
        } else {
            checkedCheckmarkColor
        }

        val duration = if (state == ToggleableState.Off) BoxOutDuration else BoxInDuration
        return animateColorAsState(target, tween(durationMillis = duration))
    }

    @Composable
    override fun boxColor(enabled: Boolean, state: ToggleableState): State<Color> {
        val target = if (enabled) {
            when (state) {
                ToggleableState.On, ToggleableState.Indeterminate -> checkedBoxColor
                ToggleableState.Off -> uncheckedBoxColor
            }
        } else {
            when (state) {
                ToggleableState.On -> disabledCheckedBoxColor
                ToggleableState.Indeterminate -> disabledIndeterminateBoxColor
                ToggleableState.Off -> disabledUncheckedBoxColor
            }
        }

        // If not enabled 'snap' to the disabled state, as there should be no animations between
        // enabled / disabled.
        return if (enabled) {
            val duration = if (state == ToggleableState.Off) BoxOutDuration else BoxInDuration
            animateColorAsState(target, tween(durationMillis = duration))
        } else {
            rememberUpdatedState(target)
        }
    }

    @Composable
    override fun borderColor(enabled: Boolean, state: ToggleableState): State<Color> {
        val target = if (enabled) {
            when (state) {
                ToggleableState.On, ToggleableState.Indeterminate -> checkedBorderColor
                ToggleableState.Off -> uncheckedBorderColor
            }
        } else {
            when (state) {
                ToggleableState.Indeterminate -> disabledIndeterminateBorderColor
                ToggleableState.On, ToggleableState.Off -> disabledBorderColor
            }
        }

        // If not enabled 'snap' to the disabled state, as there should be no animations between
        // enabled / disabled.
        return if (enabled) {
            val duration = if (state == ToggleableState.Off) BoxOutDuration else BoxInDuration
            animateColorAsState(target, tween(durationMillis = duration))
        } else {
            rememberUpdatedState(target)
        }
    }

    override fun equals(other: Any?): Boolean {
        if (this === other) return true
        if (other == null || this::class != other::class) return false

        other as DefaultCheckboxColors

        if (checkedCheckmarkColor != other.checkedCheckmarkColor) return false
        if (uncheckedCheckmarkColor != other.uncheckedCheckmarkColor) return false
        if (checkedBoxColor != other.checkedBoxColor) return false
        if (uncheckedBoxColor != other.uncheckedBoxColor) return false
        if (disabledCheckedBoxColor != other.disabledCheckedBoxColor) return false
        if (disabledUncheckedBoxColor != other.disabledUncheckedBoxColor) return false
        if (disabledIndeterminateBoxColor != other.disabledIndeterminateBoxColor) return false
        if (checkedBorderColor != other.checkedBorderColor) return false
        if (uncheckedBorderColor != other.uncheckedBorderColor) return false
        if (disabledBorderColor != other.disabledBorderColor) return false
        if (disabledIndeterminateBorderColor != other.disabledIndeterminateBorderColor) return false

        return true
    }

    override fun hashCode(): Int {
        var result = checkedCheckmarkColor.hashCode()
        result = 31 * result + uncheckedCheckmarkColor.hashCode()
        result = 31 * result + checkedBoxColor.hashCode()
        result = 31 * result + uncheckedBoxColor.hashCode()
        result = 31 * result + disabledCheckedBoxColor.hashCode()
        result = 31 * result + disabledUncheckedBoxColor.hashCode()
        result = 31 * result + disabledIndeterminateBoxColor.hashCode()
        result = 31 * result + checkedBorderColor.hashCode()
        result = 31 * result + uncheckedBorderColor.hashCode()
        result = 31 * result + disabledBorderColor.hashCode()
        result = 31 * result + disabledIndeterminateBorderColor.hashCode()
        return result
    }
}

private const val BoxInDuration = 50
private const val BoxOutDuration = 100
private const val CheckAnimationDuration = 100

// TODO(b/188529841): Update the padding and size when the Checkbox spec is finalized.
private val CheckboxDefaultPadding = 2.dp
private val CheckboxSize = 20.dp
private val StrokeWidth = 2.dp
private val RadiusSize = 2.dp