commonMain.androidx.compose.material.pullrefresh.PullRefreshIndicatorTransform.kt Maven / Gradle / Ivy

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/*
 * Copyright 2022 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.material.pullrefresh

import androidx.compose.animation.core.LinearOutSlowInEasing
import androidx.compose.material.ExperimentalMaterialApi
import androidx.compose.ui.Modifier
import androidx.compose.ui.draw.drawWithContent
import androidx.compose.ui.graphics.drawscope.clipRect
import androidx.compose.ui.graphics.graphicsLayer
import androidx.compose.ui.util.fastCoerceIn

/**
 * A modifier for translating the position and scaling the size of a pull-to-refresh indicator
 * based on the given [PullRefreshState].
 *
 * @sample androidx.compose.material.samples.PullRefreshIndicatorTransformSample
 *
 * @param state The [PullRefreshState] which determines the position of the indicator.
 * @param scale A boolean controlling whether the indicator's size scales with pull progress or not.
 */
@ExperimentalMaterialApi
// TODO: Consider whether the state parameter should be replaced with lambdas.
fun Modifier.pullRefreshIndicatorTransform(
    state: PullRefreshState,
    scale: Boolean = false,
) =
    // Essentially we only want to clip the at the top, so the indicator will not appear when
    // the position is 0. It is preferable to clip the indicator as opposed to the layout that
    // contains the indicator, as this would also end up clipping shadows drawn by items in a
    // list for example - so we leave the clipping to the scrolling container. We use MAX_VALUE
    // for the other dimensions to allow for more room for elevation / arbitrary indicators - we
    // only ever really want to clip at the top edge.
    drawWithContent {
        clipRect(
            top = 0f,
            left = -Float.MAX_VALUE,
            right = Float.MAX_VALUE,
            bottom = Float.MAX_VALUE
        ) {
            [email protected]()
        }
    }
    .graphicsLayer {
        translationY = state.position - size.height

        if (scale && !state.refreshing) {
            val scaleFraction = LinearOutSlowInEasing
                .transform(state.position / state.threshold)
                .fastCoerceIn(0f, 1f)
            scaleX = scaleFraction
            scaleY = scaleFraction
        }
    }