Ligature for spaceship operator not rendered correctly

[domi413]

The spaceship operator <=> in C++ is sometimes not rendered correctly. The rendering issue appears sporadically, and the incorrect rendering of ligatures can vary between instances. It seems like Ghostty doesn't know how to handle <=> properly under certain conditions.

Unfortunately, I don't know how to reproduce this issue yet, sorry. But here's an image to illustrate it:

Environment:

Ghostty 1.0.1-arch

Version
  - version: 1.0.1-arch
  - channel: tip
Build Config
  - Zig version: 0.13.0
  - build mode : builtin.OptimizeMode.ReleaseFast
  - app runtime: apprt.Runtime.gtk
  - font engine: font.main.Backend.fontconfig_freetype
  - renderer   : renderer.OpenGL
  - libxev     : main.Backend.io_uring
  - GTK version:
    build      : 4.16.12
    runtime    : 4.16.12
  - libadwaita : enabled
    build      : 1.6.3
    runtime    : 1.6.3
  - libX11     : enabled

I will update this report if I find a consistent way to reproduce the issue.

Thank you for looking into this!

[rhodes-b]

are you moving your cursor around? Ghostty splits ligatures between the cursor which will cause this to happen

[domi413]

The cursor isn't placed under the ligature

[mitchellh]

Ghostty splits the ligature by color too. If your syntax highlighting is changing cell color then we'd introduce a break there. A reproduction here is critical.

[00-kat]

Looks like it's the underline's fault, printf '<=> \e[4m<=\e[0m>\n' reproduced it for me.

Edit: I misinterpreted their screenshot, it was actually the change in the underline colour that's to blame; printf '<=> \e[4m\e[58;5;3m<=\e[58;5;1m>\e[0m\n' reproduced it for me.