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Merge branch 'charlesmchen/conversationRotationVsScrollContinuity'

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This commit is contained in:
Matthew Chen 2019-01-11 17:55:33 -05:00
commit 3e36dcf91f
1 changed files with 42 additions and 15 deletions
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57
Signal/src/ViewControllers/ConversationView/ConversationViewController.m
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@ -4347,23 +4347,34 @@ typedef enum : NSUInteger {
targetContentOffsetForProposedContentOffset:(CGPoint)proposedContentOffset
{
if (self.scrollContinuity == kScrollContinuityBottom && self.lastKnownDistanceFromBottom) {
// Adjust the content offset to reflect the "last known" distance
// from the bottom of the content.
CGFloat contentOffsetYBottom = self.maxContentOffsetY;
CGFloat contentOffsetY = contentOffsetYBottom - MAX(0, self.lastKnownDistanceFromBottom.floatValue);
CGFloat minContentOffsetY;
if (@available(iOS 11, *)) {
minContentOffsetY = -self.collectionView.safeAreaInsets.top;
} else {
minContentOffsetY = 0.f;
NSValue *_Nullable contentOffset =
[self contentOffsetForLastKnownDistanceFromBottom:self.lastKnownDistanceFromBottom.floatValue];
if (contentOffset) {
proposedContentOffset = contentOffset.CGPointValue;
}
contentOffsetY = MAX(minContentOffsetY, contentOffsetY);
proposedContentOffset.y = contentOffsetY;
}
return proposedContentOffset;
}
// We use this hook to ensure scroll state continuity. As the collection
// view's content size changes, we want to keep the same cells in view.
- (nullable NSValue *)contentOffsetForLastKnownDistanceFromBottom:(CGFloat)lastKnownDistanceFromBottom
{
// Adjust the content offset to reflect the "last known" distance
// from the bottom of the content.
CGFloat contentOffsetYBottom = self.maxContentOffsetY;
CGFloat contentOffsetY = contentOffsetYBottom - MAX(0, lastKnownDistanceFromBottom);
CGFloat minContentOffsetY;
if (@available(iOS 11, *)) {
minContentOffsetY = -self.collectionView.safeAreaInsets.top;
} else {
minContentOffsetY = 0.f;
}
contentOffsetY = MAX(minContentOffsetY, contentOffsetY);
return [NSValue valueWithCGPoint:CGPointMake(0, contentOffsetY)];
}
#pragma mark - Scroll State
- (BOOL)isScrolledToBottom
@ -4811,18 +4822,34 @@ typedef enum : NSUInteger {
{
[super viewWillTransitionToSize:size withTransitionCoordinator:coordinator];
// Snapshot the "last visible row".
NSIndexPath *_Nullable lastVisibleIndexPath = self.lastVisibleIndexPath;
__weak ConversationViewController *weakSelf = self;
[coordinator
animateAlongsideTransition:^(id<UIViewControllerTransitionCoordinatorContext> context) {
// Do nothing.
if (lastVisibleIndexPath) {
[self.collectionView scrollToItemAtIndexPath:lastVisibleIndexPath
atScrollPosition:UICollectionViewScrollPositionBottom
animated:NO];
}
}
completion:^(id<UIViewControllerTransitionCoordinatorContext> context) {
ConversationViewController *strongSelf = weakSelf;
if (!strongSelf) {
return;
}
// When transition animation is complete, update layout to reflect
// new size.
[weakSelf resetForSizeOrOrientationChange];
}];
[strongSelf resetForSizeOrOrientationChange];
// TODO: Ensure scroll state continuity?
if (lastVisibleIndexPath) {
[strongSelf.collectionView scrollToItemAtIndexPath:lastVisibleIndexPath
atScrollPosition:UICollectionViewScrollPositionBottom
animated:NO];
}
}];
}
- (void)traitCollectionDidChange:(nullable UITraitCollection *)previousTraitCollection