/*
* Copyright 2020 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.animation
import androidx.compose.animation.core.AnimationSpec
import androidx.compose.animation.core.VectorConverter
import androidx.compose.animation.core.spring
import androidx.compose.foundation.gestures.Scrollable
import androidx.compose.runtime.dispatch.withFrameMillis
/**
* Smooth scroll by [value] pixels.
*
* Cancels the currently running scroll, if any, and suspends until the cancellation is
* complete.
*
* @param value number of pixels to scroll by
* @param spec [AnimationSpec] to be used for this smooth scrolling
*
* @return the amount of scroll consumed
*/
suspend fun Scrollable.smoothScrollBy(
value: Float,
spec: AnimationSpec<Float> = spring()
): Float {
val animSpec = spec.vectorize(Float.VectorConverter)
val conv = Float.VectorConverter
val zeroVector = conv.convertToVector(0f)
val targetVector = conv.convertToVector(value)
var previousValue = 0f
scroll {
val startTimeMillis = withFrameMillis { it }
do {
val finished = withFrameMillis { frameTimeMillis ->
val newValue = conv.convertFromVector(
animSpec.getValue(
playTime = frameTimeMillis - startTimeMillis,
start = zeroVector,
end = targetVector,
// TODO: figure out if/how we should incorporate existing velocity
startVelocity = zeroVector
)
)
val delta = newValue - previousValue
val consumed = scrollBy(delta)
if (consumed != delta) {
previousValue += consumed
true
} else {
previousValue = newValue
previousValue == value
}
}
} while (!finished)
}
return previousValue
}
/**
* Jump instantly by [value] pixels.
*
* Cancels the currently running scroll, if any, and suspends until the cancellation is
* complete.
*
* @see smoothScrollBy for an animated version
*
* @param value number of pixels to scroll by
* @return the amount of scroll consumed
*/
suspend fun Scrollable.scrollBy(
value: Float
): Float {
var consumed = 0f
scroll {
consumed = scrollBy(value)
}
return consumed
}