TextBlock can't be right aligned

[stevenbrix]

Describe the bug

I'm trying to make a TextBlock be right aligned, where the text is always pinned to the right edge of the TextBlock and as the TextBlock is resized, trimming of the TextBlock occurs on the left side.

It sounds like FlowDirection of RightToLeft should be the property to set, along with setting TextReadingOrder to UseFlowDirection but this doesn't seem to work. The TextBlock still behaves the same way

Steps to reproduce the bug

1. Create a blank C# app
2. Add this TextBlock to the MainWindow.xaml:

        <TextBlock Text="Hi there my name is Joe and this is long text which should stick to the right side and be truncated at the left" Width="300" TextAlignment="Right" TextReadingOrder="UseFlowDirection" FlowDirection="RightToLeft"/>

Expected behavior

The end of the TextBlock is visible "stick to the right side and be truncated at the left"

Screenshots

NuGet package version

WinUI 3 - Windows App SDK 1.6.3: 1.6.241114003

Windows version

Windows 11 (24H2): Build 26100

Additional context

If there is a different way to accomplish this not through these APIs I'd be happy to do this

[Avid29]

This is not the intended purpose of TextReadingOrder or FlowDirection, you should unassign these properties and add HorizontalTextAlignment="Right" or HorizontalAlignment="Right".

Both the TextReadingOrder and FlowDirection properties pertain to right to left (RTL) languages such as Hebrew, Arabic, and Persian. FlowDirection effectively inverts the X coordinate when rendering, and TextReadingOrder states how to determine where to begin reading a sentence from.

GitHub comments use content detected to by paragraph to decide the reading order, so I will utilize that to demonstrate below.

English then Hebrew (LTR):

Hello - שלום

English with Hebrew (LTR):

This is a Hebrew word עברית and there's English after it.

Hebrew with English (LTR):

זה מילה באנגלית English ויש עברית אחריה
           ^

The Hebrew text is bugged, because you actually need to begin reading at the carrot.

Hebrew then English (RTL):

שלום - Hello

English with Hebrew (RTL):

There's a line of Hebrew before the sentence to make the paragraph right to left.

ימין לשמאל
This is a Hebrew word עברית and there's English after it.

Notice how the English text is bugged because you actually need to begin reading at "This is a ..."

Hebrew with English (RTL)

זה מילה באנגלית English ויש עברית אחריה