Undercurl cutoff

[boltlessengineer]

What Operating System(s) are you seeing this problem on?

macOS

Which Wayland compositor or X11 Window manager(s) are you using?

No response

WezTerm version

wezterm 20230224-171344-c5247d21

Did you try the latest nightly build to see if the issue is better (or worse!) than your current version?

Yes, and I updated the version box above to show the version of the nightly that I tried

Describe the bug

When using Undercurl, the line below is cut off. This makes undercurl look less squiggly. This makes distinguishing undercurl from normal underline much harder.

To Reproduce

The picture above is from Neovim, but this can be also reproduced with code from Wezterm's FAQ section.

printf "\x1b[58:2::255:0:0m\x1b[4:1msingle\x1b[4:2mdouble\x1b[4:3mcurly\x1b[4:4mdotted\x1b[4:5mdashed\x1b[0m\n"

Configuration

return {
  font = wezterm.font_with_fallback {
    'Fira Code',
  },
  font_size = 16.0,
  underline_position = "800%",
  underline_thickness = "1.5pt",
}

Expected Behavior

No response

Logs

No response

Anything else?

Currently I put my underlines at bottom end of the cells. I can just adjust the underline position more higher to fix cutoff issue, but supporting bottom-most undercurl would be nice.

Also, there was similar issue about 2 years ago. (#734)

[wez]

If you remove the underline_position from your config, do the underlines not get cut off?

[boltlessengineer]

They don't get cut off when I remove underline_position. The issue only happens when I put underline at the bottom of the cell. I want to set underline's position there because they looks great with indent-blankline.nvim Neovim plugin.

Is this intended behavior?

[wez]

Yeah, this is working as intended: the underline is pre-rendered into a cell sprite and is (very quickly) composited into underlined cells by the GPU. Your configuration makes the underline render outside the bounds of the cell sprite, so the part that is outside the bounds of the cell are clipped away.

[boltlessengineer]

So there are no way to print undercurl on top of the under cell.

How about modifying undercurl's starting position a bit? I mean like -cosine curve. I don't know exactly how undercurl is rendered, so I might be wrong. But if it is possible, we can have a continuous curve and avoid being cut off by cell boundaries.

Having this feature as an additional option would be great :)

[wez]

https://github.com/wez/wezterm/blob/1f7a34f8b259c58387392e358f5fe54c733e193a/wezterm-gui/src/glyphcache.rs#L751 is the start of the logic in the code. If you can see a way to tweak it, you're welcome to send a PR, but I have no plans to make changes to this myself at this time.

[wez]

I'm going to close this: it is working as intended, and there is nothing more for me to do at this time.

[github-actions[bot]]

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