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Optimize LazyLayout item block skipping when key didn't change
It required some experimental api changes: Remove LazyLayoutIntervalContent<T>.PinnableItem(). This abstraction doesn't help much and makes it harder to get optimizations so I refactored it by removing the function and exposing LazyLayoutIntervalContent.withInterval() instead. Item function in LazyLayoutItemProvider now accepts key in addition to index. It allows us to only get the key once instead of doing it twice on different levels. Relnote: Experimental API LazyLayoutIntervalContent now has withInterval() function. LazyLayoutIntervalContent<T>.PinnableItem() was removed. Item function in LazyLayoutItemProvider not has key as a second param. Test: LazyLayoutTest Change-Id: Ia8e2f02317a1740281257cb413a314a7089fb331
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+110
-75
lines changed

12 files changed

+110
-75
lines changed

‎compose/foundation/foundation/api/public_plus_experimental_current.txt

+2-5
Original file line numberDiff line numberDiff line change
@@ -777,6 +777,7 @@ package androidx.compose.foundation.lazy.layout {
777777
method public abstract androidx.compose.foundation.lazy.layout.IntervalList<Interval> getIntervals();
778778
method public final int getItemCount();
779779
method public final Object getKey(int index);
780+
method public final inline <T> T withInterval(int globalIndex, kotlin.jvm.functions.Function2<? super java.lang.Integer,? super Interval,? extends T> block);
780781
property public abstract androidx.compose.foundation.lazy.layout.IntervalList<Interval> intervals;
781782
property public final int itemCount;
782783
}
@@ -788,12 +789,8 @@ package androidx.compose.foundation.lazy.layout {
788789
property public default kotlin.jvm.functions.Function1<java.lang.Integer,java.lang.Object> type;
789790
}
790791

791-
public final class LazyLayoutIntervalContentKt {
792-
method @androidx.compose.foundation.ExperimentalFoundationApi @androidx.compose.runtime.Composable public static <T extends androidx.compose.foundation.lazy.layout.LazyLayoutIntervalContent.Interval> void PinnableItem(androidx.compose.foundation.lazy.layout.LazyLayoutIntervalContent<T>, int index, androidx.compose.foundation.lazy.layout.LazyLayoutPinnedItemList pinnedItemList, kotlin.jvm.functions.Function2<? super T,? super java.lang.Integer,kotlin.Unit> content);
793-
}
794-
795792
@androidx.compose.foundation.ExperimentalFoundationApi @androidx.compose.runtime.Stable public interface LazyLayoutItemProvider {
796-
method @androidx.compose.runtime.Composable public void Item(int index);
793+
method @androidx.compose.runtime.Composable public void Item(int index, Object key);
797794
method public default Object? getContentType(int index);
798795
method public default int getIndex(Object key);
799796
method public int getItemCount();

‎compose/foundation/foundation/src/androidAndroidTest/kotlin/androidx/compose/foundation/lazy/layout/LazyLayoutStateRestorationTest.kt

+1-1
Original file line numberDiff line numberDiff line change
@@ -305,7 +305,7 @@ class LazyLayoutStateRestorationTest {
305305
override val itemCount: Int = itemCount()
306306

307307
@Composable
308-
override fun Item(index: Int) {
308+
override fun Item(index: Int, key: Any) {
309309
content(index)
310310
}
311311

‎compose/foundation/foundation/src/androidAndroidTest/kotlin/androidx/compose/foundation/lazy/layout/LazyLayoutTest.kt

+36-1
Original file line numberDiff line numberDiff line change
@@ -23,6 +23,7 @@ import androidx.compose.foundation.layout.fillMaxSize
2323
import androidx.compose.runtime.Composable
2424
import androidx.compose.runtime.DisposableEffect
2525
import androidx.compose.runtime.getValue
26+
import androidx.compose.runtime.mutableStateListOf
2627
import androidx.compose.runtime.mutableStateOf
2728
import androidx.compose.runtime.setValue
2829
import androidx.compose.ui.Modifier
@@ -467,13 +468,47 @@ class LazyLayoutTest {
467468
}
468469
}
469470

471+
@Test
472+
fun skippingItemBlockWhenKeyIsObservableButDidntChange() {
473+
val stateList = mutableStateListOf(0)
474+
var itemCalls = 0
475+
val itemProvider = object : LazyLayoutItemProvider {
476+
@Composable
477+
override fun Item(index: Int, key: Any) {
478+
assertThat(index).isEqualTo(0)
479+
assertThat(key).isEqualTo(index)
480+
itemCalls++
481+
}
482+
483+
override val itemCount: Int get() = stateList.size
484+
485+
override fun getKey(index: Int) = stateList[index]
486+
}
487+
rule.setContent {
488+
LazyLayout(itemProvider) { constraint ->
489+
measure(0, constraint)
490+
layout(100, 100) {}
491+
}
492+
}
493+
494+
rule.runOnIdle {
495+
assertThat(itemCalls).isEqualTo(1)
496+
497+
stateList += 1
498+
}
499+
500+
rule.runOnIdle {
501+
assertThat(itemCalls).isEqualTo(1)
502+
}
503+
}
504+
470505
private fun itemProvider(
471506
itemCount: () -> Int,
472507
itemContent: @Composable (Int) -> Unit
473508
): LazyLayoutItemProvider {
474509
return object : LazyLayoutItemProvider {
475510
@Composable
476-
override fun Item(index: Int) {
511+
override fun Item(index: Int, key: Any) {
477512
itemContent(index)
478513
}
479514

‎compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/LazyListItemProvider.kt

+6-4
Original file line numberDiff line numberDiff line change
@@ -19,7 +19,7 @@ package androidx.compose.foundation.lazy
1919
import androidx.compose.foundation.ExperimentalFoundationApi
2020
import androidx.compose.foundation.lazy.layout.LazyLayoutItemProvider
2121
import androidx.compose.foundation.lazy.layout.LazyLayoutKeyIndexMap
22-
import androidx.compose.foundation.lazy.layout.PinnableItem
22+
import androidx.compose.foundation.lazy.layout.LazyLayoutPinnableItem
2323
import androidx.compose.foundation.lazy.layout.NearestRangeKeyIndexMapState
2424
import androidx.compose.runtime.Composable
2525
import androidx.compose.runtime.derivedStateOf
@@ -66,9 +66,11 @@ private class LazyListItemProviderImpl constructor(
6666
override val itemCount: Int get() = listContent.itemCount
6767

6868
@Composable
69-
override fun Item(index: Int) {
70-
listContent.PinnableItem(index, state.pinnedItems) { localIndex ->
71-
with(itemScope) { item(localIndex) }
69+
override fun Item(index: Int, key: Any) {
70+
LazyLayoutPinnableItem(key, index, state.pinnedItems) {
71+
listContent.withInterval(index) { localIndex, content ->
72+
content.item(itemScope, localIndex)
73+
}
7274
}
7375
}
7476

‎compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/grid/LazyGridItemProvider.kt

+5-5
Original file line numberDiff line numberDiff line change
@@ -19,7 +19,7 @@ package androidx.compose.foundation.lazy.grid
1919
import androidx.compose.foundation.ExperimentalFoundationApi
2020
import androidx.compose.foundation.lazy.layout.LazyLayoutItemProvider
2121
import androidx.compose.foundation.lazy.layout.LazyLayoutKeyIndexMap
22-
import androidx.compose.foundation.lazy.layout.PinnableItem
22+
import androidx.compose.foundation.lazy.layout.LazyLayoutPinnableItem
2323
import androidx.compose.foundation.lazy.layout.NearestRangeKeyIndexMapState
2424
import androidx.compose.runtime.Composable
2525
import androidx.compose.runtime.derivedStateOf
@@ -72,10 +72,10 @@ private class LazyGridItemProviderImpl(
7272
override fun getContentType(index: Int): Any? = gridContent.getContentType(index)
7373

7474
@Composable
75-
override fun Item(index: Int) {
76-
gridContent.PinnableItem(index, state.pinnedItems) { localIndex ->
77-
with(LazyGridItemScopeImpl) {
78-
item(localIndex)
75+
override fun Item(index: Int, key: Any) {
76+
LazyLayoutPinnableItem(key, index, state.pinnedItems) {
77+
gridContent.withInterval(index) { localIndex, content ->
78+
content.item(LazyGridItemScopeImpl, localIndex)
7979
}
8080
}
8181
}

‎compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/layout/LazyLayoutIntervalContent.kt

+20-30
Original file line numberDiff line numberDiff line change
@@ -17,7 +17,6 @@
1717
package androidx.compose.foundation.lazy.layout
1818

1919
import androidx.compose.foundation.ExperimentalFoundationApi
20-
import androidx.compose.runtime.Composable
2120

2221
/**
2322
* Common parts backing the interval-based content of lazy layout defined through `item` DSL.
@@ -26,24 +25,37 @@ import androidx.compose.runtime.Composable
2625
abstract class LazyLayoutIntervalContent<Interval : LazyLayoutIntervalContent.Interval> {
2726
abstract val intervals: IntervalList<Interval>
2827

28+
/**
29+
* The total amount of items in all the intervals.
30+
*/
2931
val itemCount: Int get() = intervals.size
3032

33+
/**
34+
* Returns item key based on a global index.
35+
*/
3136
fun getKey(index: Int): Any =
32-
withLocalIntervalIndex(index) { localIndex, content ->
37+
withInterval(index) { localIndex, content ->
3338
content.key?.invoke(localIndex) ?: getDefaultLazyLayoutKey(index)
3439
}
3540

41+
/**
42+
* Returns content type based on a global index.
43+
*/
3644
fun getContentType(index: Int): Any? =
37-
withLocalIntervalIndex(index) { localIndex, content ->
45+
withInterval(index) { localIndex, content ->
3846
content.type.invoke(localIndex)
3947
}
4048

41-
private inline fun <T> withLocalIntervalIndex(
42-
index: Int,
43-
block: (localIndex: Int, content: Interval) -> T
49+
/**
50+
* Runs a [block] on the content of the interval associated with the provided [globalIndex]
51+
* with providing a local index in the given interval.
52+
*/
53+
inline fun <T> withInterval(
54+
globalIndex: Int,
55+
block: (localIntervalIndex: Int, content: Interval) -> T
4456
): T {
45-
val interval = intervals[index]
46-
val localIntervalIndex = index - interval.startIndex
57+
val interval = intervals[globalIndex]
58+
val localIntervalIndex = globalIndex - interval.startIndex
4759
return block(localIntervalIndex, interval.value)
4860
}
4961

@@ -63,25 +75,3 @@ abstract class LazyLayoutIntervalContent<Interval : LazyLayoutIntervalContent.In
6375
val type: ((index: Int) -> Any?) get() = { null }
6476
}
6577
}
66-
67-
/**
68-
* Defines a composable content of item in a lazy layout to support focus pinning.
69-
* See [LazyLayoutPinnableItem] for more details.
70-
*/
71-
@ExperimentalFoundationApi
72-
@Composable
73-
fun <T : LazyLayoutIntervalContent.Interval> LazyLayoutIntervalContent<T>.PinnableItem(
74-
index: Int,
75-
pinnedItemList: LazyLayoutPinnedItemList,
76-
content: @Composable T.(index: Int) -> Unit
77-
) {
78-
val interval = intervals[index]
79-
val localIndex = index - interval.startIndex
80-
LazyLayoutPinnableItem(
81-
interval.value.key?.invoke(localIndex),
82-
index,
83-
pinnedItemList
84-
) {
85-
interval.value.content(localIndex)
86-
}
87-
}

‎compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/layout/LazyLayoutItemContentFactory.kt

+16-9
Original file line numberDiff line numberDiff line change
@@ -99,9 +99,12 @@ internal class LazyLayoutItemContentFactory(
9999
val indexIsUpToDate =
100100
index < itemProvider.itemCount && itemProvider.getKey(index) == key
101101
ReusableContentHost(active = indexIsUpToDate) {
102-
StableSaveProvider(StableValue(saveableStateHolder), StableValue(key)) {
103-
itemProvider.Item(index)
104-
}
102+
SkippableItem(
103+
itemProvider,
104+
StableValue(saveableStateHolder),
105+
index,
106+
StableValue(key)
107+
)
105108
}
106109
DisposableEffect(key) {
107110
onDispose {
@@ -118,14 +121,18 @@ internal class LazyLayoutItemContentFactory(
118121
private value class StableValue<T>(val value: T)
119122

120123
/**
121-
* Hack around skippable functions to force restart for unstable saveable state holder that uses
122-
* [Any] as key.
124+
* Hack around skippable functions to force skip SaveableStateProvider and Item block when
125+
* nothing changed. It allows us to skip heavy-weight composition local providers.
123126
*/
127+
@OptIn(ExperimentalFoundationApi::class)
124128
@Composable
125-
private fun StableSaveProvider(
129+
private fun SkippableItem(
130+
itemProvider: LazyLayoutItemProvider,
126131
saveableStateHolder: StableValue<SaveableStateHolder>,
127-
key: StableValue<Any>,
128-
content: @Composable () -> Unit
132+
index: Int,
133+
key: StableValue<Any>
129134
) {
130-
saveableStateHolder.value.SaveableStateProvider(key.value, content)
135+
saveableStateHolder.value.SaveableStateProvider(key.value) {
136+
itemProvider.Item(index, key.value)
137+
}
131138
}

‎compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/layout/LazyLayoutItemProvider.kt

+2-2
Original file line numberDiff line numberDiff line change
@@ -34,10 +34,10 @@ interface LazyLayoutItemProvider {
3434
val itemCount: Int
3535

3636
/**
37-
* The item for the given [index].
37+
* The item for the given [index] and [key].
3838
*/
3939
@Composable
40-
fun Item(index: Int)
40+
fun Item(index: Int, key: Any)
4141

4242
/**
4343
* Returns the content type for the item on this index. It is used to improve the item

‎compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/lazy/staggeredgrid/LazyStaggeredGridItemProvider.kt

+5-5
Original file line numberDiff line numberDiff line change
@@ -19,7 +19,7 @@ package androidx.compose.foundation.lazy.staggeredgrid
1919
import androidx.compose.foundation.ExperimentalFoundationApi
2020
import androidx.compose.foundation.lazy.layout.LazyLayoutItemProvider
2121
import androidx.compose.foundation.lazy.layout.LazyLayoutKeyIndexMap
22-
import androidx.compose.foundation.lazy.layout.PinnableItem
22+
import androidx.compose.foundation.lazy.layout.LazyLayoutPinnableItem
2323
import androidx.compose.foundation.lazy.layout.NearestRangeKeyIndexMapState
2424
import androidx.compose.runtime.Composable
2525
import androidx.compose.runtime.derivedStateOf
@@ -73,10 +73,10 @@ private class LazyStaggeredGridItemProviderImpl(
7373
override fun getContentType(index: Int): Any? = staggeredGridContent.getContentType(index)
7474

7575
@Composable
76-
override fun Item(index: Int) {
77-
staggeredGridContent.PinnableItem(index, state.pinnedItems) { localIndex ->
78-
with(LazyStaggeredGridItemScopeImpl) {
79-
item(localIndex)
76+
override fun Item(index: Int, key: Any) {
77+
LazyLayoutPinnableItem(key, index, state.pinnedItems) {
78+
staggeredGridContent.withInterval(index) { localIndex, content ->
79+
content.item(LazyStaggeredGridItemScopeImpl, localIndex)
8080
}
8181
}
8282
}

‎compose/foundation/foundation/src/commonMain/kotlin/androidx/compose/foundation/pager/LazyLayoutPager.kt

+6-4
Original file line numberDiff line numberDiff line change
@@ -32,9 +32,9 @@ import androidx.compose.foundation.lazy.layout.LazyLayout
3232
import androidx.compose.foundation.lazy.layout.LazyLayoutIntervalContent
3333
import androidx.compose.foundation.lazy.layout.LazyLayoutItemProvider
3434
import androidx.compose.foundation.lazy.layout.LazyLayoutKeyIndexMap
35+
import androidx.compose.foundation.lazy.layout.LazyLayoutPinnableItem
3536
import androidx.compose.foundation.lazy.layout.MutableIntervalList
3637
import androidx.compose.foundation.lazy.layout.NearestRangeKeyIndexMapState
37-
import androidx.compose.foundation.lazy.layout.PinnableItem
3838
import androidx.compose.foundation.lazy.layout.lazyLayoutSemantics
3939
import androidx.compose.foundation.overscroll
4040
import androidx.compose.runtime.Composable
@@ -199,9 +199,11 @@ internal class PagerLazyLayoutItemProvider(
199199
get() = pagerContent.itemCount
200200

201201
@Composable
202-
override fun Item(index: Int) {
203-
pagerContent.PinnableItem(index, state.pinnedPages) { localIndex ->
204-
item(pagerScopeImpl, localIndex)
202+
override fun Item(index: Int, key: Any) {
203+
LazyLayoutPinnableItem(key, index, state.pinnedPages) {
204+
pagerContent.withInterval(index) { localIndex, content ->
205+
content.item(pagerScopeImpl, localIndex)
206+
}
205207
}
206208
}
207209

‎tv/tv-foundation/src/main/java/androidx/tv/foundation/lazy/grid/LazyGridItemProvider.kt

+5-5
Original file line numberDiff line numberDiff line change
@@ -18,7 +18,7 @@ package androidx.tv.foundation.lazy.grid
1818

1919
import androidx.compose.foundation.ExperimentalFoundationApi
2020
import androidx.compose.foundation.lazy.layout.LazyLayoutItemProvider
21-
import androidx.compose.foundation.lazy.layout.PinnableItem
21+
import androidx.compose.foundation.lazy.layout.LazyLayoutPinnableItem
2222
import androidx.compose.runtime.Composable
2323
import androidx.compose.runtime.derivedStateOf
2424
import androidx.compose.runtime.getValue
@@ -66,10 +66,10 @@ private class LazyGridItemProviderImpl(
6666
override fun getContentType(index: Int): Any? = gridContent.getContentType(index)
6767

6868
@Composable
69-
override fun Item(index: Int) {
70-
gridContent.PinnableItem(index, state.pinnedItems) { localIndex ->
71-
with(TvLazyGridItemScopeImpl) {
72-
item(localIndex)
69+
override fun Item(index: Int, key: Any) {
70+
LazyLayoutPinnableItem(key, index, state.pinnedItems) {
71+
gridContent.withInterval(index) { localIndex, content ->
72+
content.item(TvLazyGridItemScopeImpl, localIndex)
7373
}
7474
}
7575
}

‎tv/tv-foundation/src/main/java/androidx/tv/foundation/lazy/list/LazyListItemProvider.kt

+6-4
Original file line numberDiff line numberDiff line change
@@ -18,7 +18,7 @@ package androidx.tv.foundation.lazy.list
1818

1919
import androidx.compose.foundation.ExperimentalFoundationApi
2020
import androidx.compose.foundation.lazy.layout.LazyLayoutItemProvider
21-
import androidx.compose.foundation.lazy.layout.PinnableItem
21+
import androidx.compose.foundation.lazy.layout.LazyLayoutPinnableItem
2222
import androidx.compose.runtime.Composable
2323
import androidx.compose.runtime.derivedStateOf
2424
import androidx.compose.runtime.getValue
@@ -67,9 +67,11 @@ private class LazyListItemProviderImpl constructor(
6767
override val itemCount: Int get() = listContent.itemCount
6868

6969
@Composable
70-
override fun Item(index: Int) {
71-
listContent.PinnableItem(index, state.pinnedItems) { localIndex ->
72-
with(itemScope) { item(localIndex) }
70+
override fun Item(index: Int, key: Any) {
71+
LazyLayoutPinnableItem(key, index, state.pinnedItems) {
72+
listContent.withInterval(index) { localIndex, content ->
73+
content.item(itemScope, localIndex)
74+
}
7375
}
7476
}
7577

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