Cascadia ݿ (U+077F : Arabic Letter Kaf With Two Dots Above) rendering problem in Terminal

[PhMajerus]

Windows Terminal version

1.21.1272.0

Windows build number

10.0.22631.3593 x64

Steps to reproduce

Anything that displays the character ݿ:U+077F (Arabic Letter Kaf With Two Dots Above) using Cascadia Mono or Cascadia Code in the Terminal.

echo -e "\n\n\n\n\n\n \u0643 \u077F \n\n\n\n\n\n"

It seems to only happen in Terminal, Word does not stretch that glyph:

(beware characters order looks reversed because Word shows them RTL)

And this seems to only happen with Cascadia, here is the same terminal with the font changed to Iosevka:

And the glyph looks fine in VTT as well:

Also, that glyph is a combination of other glyphs, and ك:kaf-ar, which is U+0643, shown alongside in the screenshots and test command, does not get stretched/mirrored.

Expected Behavior

The ݿ:U+077F glyph should look like ك:U+0643 with two extra dots above it.

Actual Behavior

The ݿ:U+077F glyph is rendered stretched and mirrored, or corrupt.

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• Weird glyph rendering issue with CaskaydiaCove NerdFont (#16413), similarity score: 0.75

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[lhecker]

I've checked this glyph out under a debugger, and this weird shape is what we get back from the Direct2D API. There's no matrix transformation, or any other kind of unusual configuration active when this happens.

I've also found that the issue goes away at a font size of 38pt at 100% display scale (26pt at 150% scale, and so on). This indicates that the issue is with grid fitting, because at very large font sizes glyphs are rendered from their outlines only. And indeed, using DWRITE_RENDERING_MODE_OUTLINE solves the issue.

If you check the rendering in VTT you'll see that it shows the exact same issue if you enable Grid Fit (Ctrl+G):

xtUGubqfjgYygqLz.mp4

[PhMajerus]

Thanks for looking into this @lhecker

I just read through Cascadia issues and there seems to have been an issue report related to this: microsoft/cascadia-code#743
I guess there is something wrong with the Arabic glyphs in the font.

[DHowett]

Oh yeah, that's broken. Gonna close this in favor of the one on the Cascadia repo. Thanks!