oxen-io
/
session-ios
mirror of https://github.com/oxen-io/session-ios.git
1
0
Fork 0
Code Issues Projects Releases Wiki Activity

Restore scroll state after resetting the conversation view's mapping. 

// FREEBIE
This commit is contained in:
Matthew Chen 2017-08-31 15:13:00 -04:00
parent 7d32491968
commit b2c8ad2d29
1 changed files with 23 additions and 0 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

23
Signal/src/ViewControllers/ConversationView/MessagesViewController.m
View File

@ -4436,7 +4436,30 @@ typedef NS_ENUM(NSInteger, MessagesRangeSizeMode) {
_shouldObserveDBModifications = shouldObserveDBModifications;
if (self.shouldObserveDBModifications) {
// We need to call resetMappings when we _resume_ observing DB modifications,
// since we've been ignore DB modifications so the mappings can be wrong.
//
// resetMappings can however have the side effect of increasing the mapping's
// "window" size. If that happens, we need to restore the scroll state.
// Snapshot the scroll state by measuring the "distance from top of view to
// bottom of content"; if the mapping's "window" size grows, it will grow
// _upward_.
CGFloat viewTopToContentBottom = self.collectionView.contentSize.height - self.collectionView.contentOffset.y;
NSUInteger oldCellCount = [self.messageMappings numberOfItemsInGroup:self.thread.uniqueId];
[self resetMappings];
NSUInteger newCellCount = [self.messageMappings numberOfItemsInGroup:self.thread.uniqueId];
// Detect changes in the mapping's "window" size.
if (oldCellCount != newCellCount) {
// There's no way to imperatively force the collection view to layout its
// content, but we can safely use `collectionViewContentSize` to determine
// the new content size.
CGSize newContentSize = [self.collectionView.collectionViewLayout collectionViewContentSize];
CGPoint newContentOffset = CGPointMake(0, MAX(0, newContentSize.height - viewTopToContentBottom));
[self.collectionView setContentOffset:newContentOffset animated:NO];
}
}
}