LazySemantics.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.lazy.grid
import androidx.compose.foundation.ExperimentalFoundationApi
import androidx.compose.foundation.gestures.animateScrollBy
import androidx.compose.foundation.lazy.layout.LazyLayoutItemProvider
import androidx.compose.foundation.lazy.layout.LazyLayoutSemanticState
import androidx.compose.runtime.Composable
import androidx.compose.runtime.getValue
import androidx.compose.runtime.remember
import androidx.compose.ui.semantics.CollectionInfo
import androidx.compose.ui.semantics.ScrollAxisRange
@OptIn(ExperimentalFoundationApi::class)
@Composable
internal fun rememberLazyGridSemanticState(
state: LazyGridState,
itemProvider: LazyLayoutItemProvider,
reverseScrolling: Boolean
): LazyLayoutSemanticState =
remember(state, itemProvider, reverseScrolling) {
object : LazyLayoutSemanticState {
override fun scrollAxisRange(): ScrollAxisRange =
ScrollAxisRange(
value = {
// This is a simple way of representing the current position without
// needing any lazy items to be measured. It's good enough so far, because
// screen-readers care mostly about whether scroll position changed or not
// rather than the actual offset in pixels.
state.firstVisibleItemIndex + state.firstVisibleItemScrollOffset / 100_000f
},
maxValue = {
if (state.canScrollForward) {
// If we can scroll further, we don't know the end yet,
// but it's upper bounded by #items + 1
itemProvider.itemCount + 1f
} else {
// If we can't scroll further, the current value is the max
state.firstVisibleItemIndex +
state.firstVisibleItemScrollOffset / 100_000f
}
},
reverseScrolling = reverseScrolling
)
override suspend fun animateScrollBy(delta: Float) {
state.animateScrollBy(delta)
}
override suspend fun scrollToItem(index: Int) {
state.scrollToItem(index)
}
// TODO(popam): check if this is correct - it would be nice to provide correct columns
override fun collectionInfo(): CollectionInfo =
CollectionInfo(rowCount = -1, columnCount = -1)
}
}