[Bug] Labels take too much vertical space with LineBreakMode TailTruncation since Xamarin.Forms 4.8.0

[radioactiveman]

Description

Steps to Reproduce

1. Add a label to a collection (ListView, Bindable StackLayout, ...)
2. Set LineBreakMode to TailTruncation
3. Set Text to a long string which does not fit the screen width

Expected Behavior

All collection items have the same height. This is the case with Xamarin.Forms until 4.7.0.

Actual Behavior

Items with too long labels have a heigher height than others. This is a regression in Xamarin.Forms 4.8.0.
It occurs on Android and iOS (UWP not tested).

Basic Information

• Version with issue: 4.8.0.1269 (latest stable)
• Last known good version: 4.7.0.1260
• IDE: Visual Studio 2019
• Platform Target Frameworks:
  • iOS: Default version
  • Android: 9.0

Screenshots

Xamarin.Forms 4.7.0 (same heights):

Xamarin.Forms 4.8.0 (different height for second item, causing greater gaps):

Reproduction Link

App1.zip

[cmpalmer66]

I'm not sure if it's related, but I've also seen a bug I'm trying to isolate where, if the label contains nothing but an acronym or a camel-cased word, the word wrapping can get confused and allocate too much vertical space to contain it. In our application, a label such as "MixedCaseWord" or "MAOP" will result in extra vertical space, whereas "Mixed Case Word" or "M A O P" will not.

[Tommigun1980]

Hi @cmpalmer66 - could you please check #11713 whether that is the bug you are describing? If it is, I don't think it has to do with actual word content, but rather that different text content on different screens would get a line break in different places, and some of them just happen to hit the 'sweet spot' for this bug to appear. Hence I think it is impossible to find something that works on all devices until this gets fixed, in case it is indeed the same issue.

[cmpalmer66]

Hi @cmpalmer66 - could you please check #11713 whether that is the bug you are describing? If it is, I don't think it has to do with actual word content, but rather that different text content on different screens would get a line break in different places, and some of them just happen to hit the 'sweet spot' for this bug to appear. Hence I think it is impossible to find something that works on all devices until this gets fixed, in case it is indeed the same issue.

I think it might be related, but in my case, I'm specifically seeing a problem with WordWrap turned on and short words/text that doesn't wrap. For example, a short string like "The caption" doesn't grab any extra vertical space, but one with an acronym, like "MAOP" is also not wrapping, but has extra space below the label. I need to figure out a demo repo and maybe post it as a separate issue - I'm just guessing that it's related to this issue or #11713.

[radioactiveman]

This is probably related to #11903. But since there is no new Xamarin.Forms version available yet, I am not able to verify this for now.

[radioactiveman]

Closing since this is indeed related to #11903 and fixed with Xamarin.Forms 4.8.0.1364.