Fix showing ellipsis when word wrap and limited by height or MaxLines

[appel1]

What does the pull request do?

Fixes a bug

What is the current behavior?

Ellipsis is not shown when text is truncated when the TextBlock is limited by height or MaxLines.

What is the updated/expected behavior with this PR?

Ellipsis is shown when text is truncated.

Fixed issues

Fixes #17633

[Gillibald]

A duplicate of #22017

This PR also complicates things a lot for no reason. Pass the last visible line's width as the collapsing width, and it will correctly collapse.

[appel1]

Oh well, thought I had checked for other PRs, but obviously I failed. If the other one solves the issues we can just drop this one.

[avaloniaui-bot]

You can test this PR using the following package version. 12.2.999-cibuild0068575-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[appel1]

With the #22017 PR the following tests I added fails. I don't think it is intended behavior.

1.  Avalonia.Controls.UnitTests.TextBlockTests.TextBlock_With_MaxLines_And_Hidden_Content_After_NewLine_Should_Show_Ellipsis 

Assert.Contains() Failure: Sub-string not found
String:    "second line\r\n"
Not found: "…"
  at TextBlockTests.TextBlock_With_MaxLines_And_Hidden_Content_After_NewLine_Should_Show_Ellipsis() line 879

2.  Avalonia.Controls.UnitTests.TextBlockTests.TextBlock_With_MaxLines_And_Hidden_Content_After_NewLine_Should_Show_Ellipsis_WordEllipsis 

Assert.Contains() Failure: Sub-string not found
String:    "second line\r\n"
Not found: "…"
  at TextBlockTests.TextBlock_With_MaxLines_And_Hidden_Content_After_NewLine_Should_Show_Ellipsis_WordEllipsis() line 912

3.  Avalonia.Controls.UnitTests.TextBlockTests.TextBlock_With_Wrap_CharacterEllipsis_And_Height_Limit_Should_Show_Ellipsis_On_Last_Line 

Assert.Contains() Failure: Sub-string not found
String:    "Lorem ipsum dolor sit amet, "
Not found: "…"
  at TextBlockTests.TextBlock_With_Wrap_CharacterEllipsis_And_Height_Limit_Should_Show_Ellipsis_On_Last_Line() line 694

4.  Avalonia.Controls.UnitTests.TextBlockTests.TextBlock_With_Wrap_WordEllipsis_And_Height_Limit_Should_Show_Ellipsis_On_Last_Line 

Assert.Contains() Failure: Sub-string not found
String:    "Lorem ipsum dolor sit amet, "
Not found: "…"
  at TextBlockTests.TextBlock_With_Wrap_WordEllipsis_And_Height_Limit_Should_Show_Ellipsis_On_Last_Line() line 764

5.  Avalonia.Controls.UnitTests.TextBlockTests.TextBlock_With_MaxHeight_And_Hidden_Content_After_NewLine_Should_Show_Ellipsis 

Assert.Contains() Failure: Sub-string not found
String:    "second line\r\n"
Not found: "…"
  at TextBlockTests.TextBlock_With_MaxHeight_And_Hidden_Content_After_NewLine_Should_Show_Ellipsis() line 948

[avaloniaui-bot]

You can test this PR using the following package version. 12.2.999-cibuild0068581-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[puk06]

With the #22017 PR the following tests I added fails. I don't think it is intended behavior.

1.  Avalonia.Controls.UnitTests.TextBlockTests.TextBlock_With_MaxLines_And_Hidden_Content_After_NewLine_Should_Show_Ellipsis 

Assert.Contains() Failure: Sub-string not found
String:    "second line\r\n"
Not found: "…"
  at TextBlockTests.TextBlock_With_MaxLines_And_Hidden_Content_After_NewLine_Should_Show_Ellipsis() line 879

2.  Avalonia.Controls.UnitTests.TextBlockTests.TextBlock_With_MaxLines_And_Hidden_Content_After_NewLine_Should_Show_Ellipsis_WordEllipsis 

Assert.Contains() Failure: Sub-string not found
String:    "second line\r\n"
Not found: "…"
  at TextBlockTests.TextBlock_With_MaxLines_And_Hidden_Content_After_NewLine_Should_Show_Ellipsis_WordEllipsis() line 912

3.  Avalonia.Controls.UnitTests.TextBlockTests.TextBlock_With_Wrap_CharacterEllipsis_And_Height_Limit_Should_Show_Ellipsis_On_Last_Line 

Assert.Contains() Failure: Sub-string not found
String:    "Lorem ipsum dolor sit amet, "
Not found: "…"
  at TextBlockTests.TextBlock_With_Wrap_CharacterEllipsis_And_Height_Limit_Should_Show_Ellipsis_On_Last_Line() line 694

4.  Avalonia.Controls.UnitTests.TextBlockTests.TextBlock_With_Wrap_WordEllipsis_And_Height_Limit_Should_Show_Ellipsis_On_Last_Line 

Assert.Contains() Failure: Sub-string not found
String:    "Lorem ipsum dolor sit amet, "
Not found: "…"
  at TextBlockTests.TextBlock_With_Wrap_WordEllipsis_And_Height_Limit_Should_Show_Ellipsis_On_Last_Line() line 764

5.  Avalonia.Controls.UnitTests.TextBlockTests.TextBlock_With_MaxHeight_And_Hidden_Content_After_NewLine_Should_Show_Ellipsis 

Assert.Contains() Failure: Sub-string not found
String:    "second line\r\n"
Not found: "…"
  at TextBlockTests.TextBlock_With_MaxHeight_And_Hidden_Content_After_NewLine_Should_Show_Ellipsis() line 948

The changes in my pull request only address issues with the previous implementation; the handling of manual line breaks (\r\n) remains unchanged. As before, ellipses are displayed only when a string is wrapped (IsSplit = true).

Since IsSplit is set to true only when a line break occurs via WrappingTextLineBreak, it should be set to false for manual line breaks, meaning the ellipsis should not be displayed. I apologize if I’m mistaken.

[appel1]

I updated the PR so that a height limit clips silently (no  … ) when the last visible line ends at a hard paragraph break — matching WPF and CSS max-height + overflow:hidden.

Scenario	#22017	This PR
Wrapped text cut by MaxLines	✅	✅
Wrapped text cut by MaxHeight	❌	✅
Double …… prevention	❌	✅
Hard breaks hidden by MaxLines — shows …	❌	✅

A question here is if MaxLines + TextTrimming should show  …  when content is hidden only due to the line count limit (last visible line fits the width)? CSS line-clamp does. WPF doesn't have this feature.

[avaloniaui-bot]

You can test this PR using the following package version. 12.2.999-cibuild0068613-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]

[appel1]

Rebased onto latest main (which now includes merged #22017). Note that #22017 only fixed the MaxLines collapsing width (using the layout-wide width instead of the specific line's width); this PR fixes that plus the equivalent MaxHeight case, adds a wrap-split vs. hard-paragraph-break distinction (matching WPF/HTML overflow:hidden clip behavior when the last visible line isn't itself trimmed), guards against double-ellipsis when text already overflowed, and covers RTL wrapped MaxLines.

[avaloniaui-bot]

You can test this PR using the following package version. 12.2.999-cibuild0068968-alpha. (feed url: https://nuget-feed-all.avaloniaui.net/v3/index.json) [PRBUILDID]