/*
* 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.gestures
import androidx.compose.runtime.Composable
import androidx.compose.ui.Modifier
import androidx.compose.ui.geometry.Offset
import androidx.compose.ui.geometry.Size
import androidx.compose.ui.graphics.drawscope.DrawScope
import androidx.compose.ui.input.nestedscroll.NestedScrollSource
import androidx.compose.ui.unit.Velocity
/**
* Controller to control the overscroll logic for a particular scrollable container.
*/
internal interface OverScrollController {
/**
* Release overscroll effects from being bounded by the current scroll cycle.
*
* This is usually called when effects are no longer matter for a particular pointer
* interaction and is called on pointer UP or any radical change that requires reinitialisation.
*/
fun release()
/**
* Consume any overscroll before the scroll happens if needed.
*
* This is usually relevant when the overscroll expresses the effect that is needed to be
* negated first before actually scrolling. The example might be a spring-based overscroll,
* where you want to release the tension of a spring before starting to scroll to provide a
* good user-experience.
*
* @param scrollDelta the original delta to scroll
* @param pointerPosition position of the pointer causing the scroll, if known
* @param source source of the scroll event
*
* @return the amount of scroll consumed that won't be available for scrollable container
* anymore
*/
fun consumePreScroll(
scrollDelta: Offset,
pointerPosition: Offset?,
source: NestedScrollSource
): Offset
/**
* Process scroll delta that is available after the scroll iteration is over.
*
* This is the main method to show an overscroll, as [overScrollDelta] will be a
* non-[zero][Offset.Zero] only if the scroll is happening at the bound of a scrollable
* container.
*
* @param initialDragDelta initial drag delta before any consumption was made
* @param overScrollDelta the amount of overscroll left after the scroll process
* @param pointerPosition the pointer location in the bounds of the container
* @param source source of the scroll event
*/
fun consumePostScroll(
initialDragDelta: Offset,
overScrollDelta: Offset,
pointerPosition: Offset?,
source: NestedScrollSource
)
/**
* Consume any velocity for the over scroll effect before the fling happens.
*
* relevant when the overscroll expresses the effect that is needed to be
* negated (or increased) first before actually scrolling. The example might be a spring-based
* overscroll, where you want to release the tension of a spring before starting to scroll to
* provide a good user-experience.
*
* @param velocity velocity available to a scrolling container before flinging
*
* @return the amount of velocity that overscroll effect consumed that won't be available for
* fling operation
*/
fun consumePreFling(
velocity: Velocity
): Velocity
/**
* Feed and process velocity overscroll to show an effect.
*
* @param velocity the amount of velocity that is left for overscroll after the fling happened.
*/
fun consumePostFling(velocity: Velocity)
/**
* Set information regarding scrollable container for overscroll.
*
* @param size the size of the container that scrolls
* @param isContentScrolls whether content can scroll within the scrollable container or not
*/
fun refreshContainerInfo(size: Size, isContentScrolls: Boolean)
/**
* Stop overscroll animation (if happening)
*
* @return true if there was an animation that has been stopped, false if there was no
* animation.
*/
fun stopOverscrollAnimation(): Boolean
/**
* Draw the overscroll effect.
*/
fun DrawScope.drawOverScroll()
}
@Composable
internal expect fun rememberOverScrollController(): OverScrollController
internal expect fun Modifier.overScroll(overScrollController: OverScrollController): Modifier