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Optimize for horizontal scrolling UICollectionView. #37

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Optimize for horizontal scrolling UICollectionView. #37

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28 changes: 15 additions & 13 deletions UICollectionViewLeftAlignedLayout/Sources/UICollectionViewLeftAlignedLayout.m
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Original file line number Diff line number Diff line change
Expand Up @@ -70,19 +70,21 @@ - (UICollectionViewLayoutAttributes *)layoutAttributesForItemAtIndexPath:(NSInde
NSIndexPath* previousIndexPath = [NSIndexPath indexPathForItem:indexPath.item-1 inSection:indexPath.section];
CGRect previousFrame = [self layoutAttributesForItemAtIndexPath:previousIndexPath].frame;
CGFloat previousFrameRightPoint = previousFrame.origin.x + previousFrame.size.width;
CGRect currentFrame = currentItemAttributes.frame;
CGRect strecthedCurrentFrame = CGRectMake(sectionInset.left,
currentFrame.origin.y,
layoutWidth,
currentFrame.size.height);
// if the current frame, once left aligned to the left and stretched to the full collection view
// width intersects the previous frame then they are on the same line
BOOL isFirstItemInRow = !CGRectIntersectsRect(previousFrame, strecthedCurrentFrame);

if (isFirstItemInRow) {
// make sure the first item on a line is left aligned
[currentItemAttributes leftAlignFrameWithSectionInset:sectionInset];
return currentItemAttributes;
// Only work with UICollectionViewScrollDirectionVertical
if (self.scrollDirection == UICollectionViewScrollDirectionVertical) {
CGRect currentFrame = currentItemAttributes.frame;
CGRect strecthedCurrentFrame = CGRectMake(sectionInset.left,
currentFrame.origin.y,
layoutWidth,
currentFrame.size.height);
// if the current frame, once left aligned to the left and stretched to the full collection view
// width intersects the previous frame then they are on the same line
BOOL isFirstItemInRow = !CGRectIntersectsRect(previousFrame, strecthedCurrentFrame);
if (isFirstItemInRow) {
// make sure the first item on a line is left aligned
[currentItemAttributes leftAlignFrameWithSectionInset:sectionInset];
return currentItemAttributes;
}
}

CGRect frame = currentItemAttributes.frame;
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