Certain nerdfont characters suddenly large when they're supposed to be small

[johnnyggalt]

Issue Description

Certain nerdfont icons, like \udb82\udf3a and \udb82\udf3b are suddenly appearing much larger than they're supposed to:

Notice the first two characters appearing much larger than they should, and how other NF icons appear correctly alongside them. Those same faulty characters appear fine elsewhere (this is the built-in Terminal but I also checked in VS Code):

And Ghostty was also displaying them perfectly until recently, so I guess there was an update that broke this.

Expected Behavior

The numerical NF icons I'm using should appear at a much smaller size than they are.

Actual Behavior

Those specific numerical NF icons are appearing much too large, even though other similar icons appear correctly.

Reproduction Steps

1. Open Ghostty
2. Copy an icon from the NF cheat sheet (I just searched for "1" or "2")
3. Paste into Ghostty

Ghostty Logs

N/A

Ghostty Version

Ghostty 1.2.2-1.fc42

Version
  - version: 1.2.2-1.fc42
  - channel: tip
Build Config
  - Zig version   : 0.14.1
  - build mode    : builtin.OptimizeMode.ReleaseFast
  - app runtime   : apprt.Runtime.gtk
  - font engine   : font.main.Backend.fontconfig_freetype
  - renderer      : renderer.generic.Renderer(renderer.OpenGL)
  - libxev        : io_uring
  - kernel version: 6.16.10-200.fc42.x86_64
  - desktop env   : gnome
  - GTK version   :
    build         : 4.18.6
    runtime       : 4.18.6
  - libadwaita    : enabled
    build         : 1.7.7
    runtime       : 1.7.7
  - libX11        : enabled
  - libwayland    : enabled

### OS Version Information

Fedora Silverblue 42

### (Linux only) Display Server

Wayland

### (Linux only) Desktop Environment/Window Manager

Gnome 48

### Minimal Ghostty Configuration

```ini
# no config required

### Additional Relevant Configuration

_No response_

### I acknowledge that:

- [X] I have reviewed the FAQ and confirm that my issue is NOT among them.
- [X] I have searched the Ghostty repository (both open and closed Discussions and Issues) and confirm this is not a duplicate of an existing issue or discussion.
- [X] I have checked the "Preview" tab on all text fields to ensure that everything looks right, and have wrapped all configuration and code in code blocks with a group of three backticks (` ``` `) on separate lines.

[danielwe]

Thanks for the feedback! The weird thing about these particular letter/number icons is that the monospace version that you get if you don't put a space after them was always this big. Try using SomeFont Nerd Font Mono instead of SomeFont Nerd Font in VSCode or Terminal.app and you'll see the same large sizes. However, the "full-size" variants used to be tiny as in your second screenshot.

Read that again: you'd give an icon more space and it would shrink.

It was a deliberate change to make it so that, in Ghostty, the full-size icon is never smaller than its monospace version. I've also submitted a pull request upstream to Nerd Fonts, suggesting they do the same when patching fonts: ryanoasis/nerd-fonts#1926.

However, if this proves unpopular I guess it's something to reconsider.

[danielwe]

What I hadn't considered before but is clear from your screenshot is that there may be an intention behind the commensurate sizes of characters with and without circles/squares (though, as noted, this was already broken in monospaced nerd fonts). The actual solution for this within Nerd Fonts is to put such glyph families in a common scale group. However, these particular icons originated in the Material Design font, and no one has taken on the daunting task of defining scale groups for that font yet. It's almost 7000 icons.

I guess I'll mull over this for a little while. @johnnyggalt let me know if you have any thoughts in response to all of this.