Text messages bubble width changes after scrolling

[ElrB]

Hi @ekazaev

Please see attached video. It looks like sometimes the width of some text messages changes after scrolling. My code is purely off the example app.

https://github.com/user-attachments/assets/727279fb-13c1-46d7-b547-549801d7d56e

[ekazaev]

Hi @ElrB

I can only suggest that you have the first time layout issue when the label or UITextView doesnt return correct width/height. Later when the cell size propogated again - it layouts correctly and returns correct size to the collection view.

Check the attributes returned from preferredLayoutAttributesFitting.

If your code is based on example app - it should be easy to reproduce it there. Modify it the same way and I can look after.

[ElrB]

Hi @ekazaev

I forgot to mention that this issue only happens to one line text messages that have a width close to (viewPortWidth * MessageLayoutConstants.maxWidth).

Where should I check the preferredLayoutAttributesFitting?

Thanks.

[ekazaev]

@ElrB In the UICollectionViewCell

[ElrB]

Hi @ekazaev

I check preferredLayoutAttributesFitting in createTextCell method like (hopefully I did check correctly) -

if let layout = collectionView.collectionViewLayout as? CollectionViewChatLayout, let attributes = layout.layoutAttributesForItem(at: indexPath) { print("message: ", message.messageCoreInformation.message) print("attributes: ", cell.preferredLayoutAttributesFitting(attributes)) }

Below is a print out of the attributes before and after scrolling (same message that has issue)

Before -

After -

[ekazaev]

Well. On your video it seems opposite. But we see that the height 60 doesnt look like what you expect. What preferredLayoutAttributesFitting does if it is not modified is uses systemLayoutSizeFitting on the content view of your cell. And for some reason it gets the wrong size. I would check the constraints and so on. If you are using the UIlabel which I dont recommend - check that you are setting preferredMaxLayoutWidth. It is usually the issue with labels. PS: But there is technically nothing to do with the collection view or layout. Collection view asks cell for its preferred size -> cell reports its preffered size -> collection view using the layout allocates it on the screen accordingly.

[ElrB]

Hi @ekazaev

I figured viewPortWidth = layoutAttributes.layoutFrame.width was somehow not getting the correct width when view is first push onto screen. So I replaced it with private var viewPortWidth: CGFloat = ScreenSize.Width and solved the issue.

[ekazaev]

@ElrB It is not good enough solution. Because if you start to integrate your view into the split controller for ipad for example - it wont be a correct width. It is normal that when the view controller is not yet appeared it doesnt know its correct size, that why collection view in it doesnt set values you expect. You need to make sure you call something to ivalidate layout after the view got a coorect size.

[ElrB]

@ekazaev you are right, I forgot about split vc's and iPad. For now I have restricted the app to only portrait mode and did not use split vc's. Will it be fine for now?

Currently collectionView.collectionViewLayout.invalidateLayout() is already called in view did appear, but does not solve issue. Not sure what to do anymore. I just don't know why its not getting correct size if am calling process updates in viewDidLayoutSubviews :(