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[ASCollectionView] Only remeasure all nodes if bounds changed in a fixed dimension (#2343)

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This commit is contained in:
Adlai Holler
2016-10-04 18:12:34 -04:00
committed by GitHub
parent 872aad220f
commit ba2e12010b
1 changed files with 27 additions and 10 deletions
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37
AsyncDisplayKit/ASCollectionView.mm
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@@ -1321,7 +1321,8 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
*/
- (void)layer:(CALayer *)layer didChangeBoundsWithOldValue:(CGRect)oldBounds newValue:(CGRect)newBounds
{
if (CGSizeEqualToSize(_lastBoundsSizeUsedForMeasuringNodes, newBounds.size)) {
CGSize lastUsedSize = _lastBoundsSizeUsedForMeasuringNodes;
if (CGSizeEqualToSize(lastUsedSize, newBounds.size)) {
return;
}
_lastBoundsSizeUsedForMeasuringNodes = newBounds.size;
@@ -1331,15 +1332,31 @@ static NSString * const kCellReuseIdentifier = @"_ASCollectionViewCell";
if (_ignoreNextBoundsSizeChangeForMeasuringNodes) {
_ignoreNextBoundsSizeChangeForMeasuringNodes = NO;
} else {
// This actually doesn't perform an animation, but prevents the transaction block from being processed in the
// data controller's prevent animation block that would interrupt an interrupted relayout happening in an animation block
// ie. ASCollectionView bounds change on rotation or multi-tasking split view resize.
[self performBatchAnimated:YES updates:^{
[_dataController relayoutAllNodes];
} completion:nil];
// We need to ensure the size requery is done before we update our layout.
[self waitUntilAllUpdatesAreCommitted];
[self.collectionViewLayout invalidateLayout];
// Laying out all nodes is expensive, and performing an empty update may be unsafe
// if the data source has pending changes that it hasn't reported yet – the collection
// view will requery the new counts and expect them to match the previous counts.
//
// We only need to do this if the bounds changed in the non-scrollable direction.
// If, for example, a vertical flow layout has its height changed due to a status bar
// appearance update, we do not need to relayout all nodes.
// For a more permanent fix to the unsafety mentioned above, see https://github.com/facebook/AsyncDisplayKit/pull/2182
ASScrollDirection scrollDirection = self.scrollableDirections;
BOOL fixedVertically = (ASScrollDirectionContainsVerticalDirection(scrollDirection) == NO);
BOOL fixedHorizontally = (ASScrollDirectionContainsHorizontalDirection(scrollDirection) == NO);
BOOL changedInNonScrollingDirection = (fixedHorizontally && newBounds.size.width != lastUsedSize.width) || (fixedVertically && newBounds.size.height != lastUsedSize.height);
if (changedInNonScrollingDirection) {
// This actually doesn't perform an animation, but prevents the transaction block from being processed in the
// data controller's prevent animation block that would interrupt an interrupted relayout happening in an animation block
// ie. ASCollectionView bounds change on rotation or multi-tasking split view resize.
[self performBatchAnimated:YES updates:^{
[_dataController relayoutAllNodes];
} completion:nil];
// We need to ensure the size requery is done before we update our layout.
[self waitUntilAllUpdatesAreCommitted];
[self.collectionViewLayout invalidateLayout];
}
}
}