91 lines
3.3 KiB
Objective-C
91 lines
3.3 KiB
Objective-C
//
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// Copyright (c) 2019 Open Whisper Systems. All rights reserved.
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//
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#import "ConversationCollectionView.h"
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NS_ASSUME_NONNULL_BEGIN
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#pragma mark -
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@implementation ConversationCollectionView
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- (void)setFrame:(CGRect)frame
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{
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if (frame.size.width == 0 || frame.size.height == 0) {
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// Ignore iOS Auto Layout's tendency to temporarily zero out the
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// frame of this view during the layout process.
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//
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// The conversation view has an invariant that the collection view
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// should always have a "reasonable" (correct width, non-zero height)
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// size. This lets us manipulate scroll state at all times, especially
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// before the view has been presented for the first time. This
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// invariant also saves us from needing all sorts of ugly and incomplete
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// hacks in the conversation view's code.
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return;
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}
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CGSize oldSize = self.frame.size;
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CGSize newSize = frame.size;
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BOOL isChanging = !CGSizeEqualToSize(oldSize, newSize);
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if (isChanging) {
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[self.layoutDelegate collectionViewWillChangeSizeFrom:oldSize to:newSize];
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}
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[super setFrame:frame];
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if (isChanging) {
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[self.layoutDelegate collectionViewDidChangeSizeFrom:oldSize to:newSize];
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}
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}
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- (void)setBounds:(CGRect)bounds
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{
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if (bounds.size.width == 0 || bounds.size.height == 0) {
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// Ignore iOS Auto Layout's tendency to temporarily zero out the
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// frame of this view during the layout process.
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//
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// The conversation view has an invariant that the collection view
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// should always have a "reasonable" (correct width, non-zero height)
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// size. This lets us manipulate scroll state at all times, especially
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// before the view has been presented for the first time. This
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// invariant also saves us from needing all sorts of ugly and incomplete
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// hacks in the conversation view's code.
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return;
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}
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CGSize oldSize = self.bounds.size;
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CGSize newSize = bounds.size;
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BOOL isChanging = !CGSizeEqualToSize(oldSize, newSize);
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if (isChanging) {
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[self.layoutDelegate collectionViewWillChangeSizeFrom:oldSize to:newSize];
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}
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[super setBounds:bounds];
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if (isChanging) {
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[self.layoutDelegate collectionViewDidChangeSizeFrom:oldSize to:newSize];
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}
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}
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- (void)setContentOffset:(CGPoint)contentOffset
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{
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if (self.contentSize.height < 1 && CGPointEqualToPoint(CGPointZero, contentOffset)) {
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// [UIScrollView _adjustContentOffsetIfNecessary] resets the content
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// offset to zero under a number of undocumented conditions. We don't
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// want this behavior; we want fine-grained control over the default
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// scroll state of the message view.
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//
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// [UIScrollView _adjustContentOffsetIfNecessary] is called in
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// response to many different events; trying to prevent them all is
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// whack-a-mole.
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//
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// It's not safe to override [UIScrollView _adjustContentOffsetIfNecessary],
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// since its a private API.
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//
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// We can avoid the issue by simply ignoring attempt to reset the content
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// offset to zero before the collection view has determined its content size.
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return;
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}
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[super setContentOffset:contentOffset];
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}
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@end
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NS_ASSUME_NONNULL_END
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