Ligature support

[bts]

Thanks for this project! What would be necessary for us to add ligature support to termonad? e.g. for the font PragmataPro

[cdepillabout]

@bts I'm not very familiar with ligature support, or how it is handled in the Gnome ecosystem.

Termonad is using the VTE library, which is a terminal emulator from the Gnome team exposed as a GTK widget.

The Terminal from the VTE library exposes a method to set a FontDescription for the terminal:

https://hackage.haskell.org/package/gi-vte-2.91.19/docs/GI-Vte-Objects-Terminal.html#g:87

This method is called by Termonad when creating a new Terminal:

termonad/src/Termonad/Term.hs

Line 303 in 2588524

terminalSetFont vteTerm (Just tmStateFontDesc)

The FontDescription in question is created here:

termonad/src/Termonad/App.hs

Lines 152 to 162 in 2588524

	createFontDesc :: TMConfig -> IO FontDescription
	createFontDesc tmConfig = do
	fontDesc <- fontDescriptionNew
	let fontConf = tmConfig ^. lensOptions . lensFontConfig
	fontDescriptionSetFamily fontDesc (fontFamily fontConf)
	case fontSize fontConf of
	FontSizePoints points ->
	fontDescriptionSetSize fontDesc $ fromIntegral (points * fromIntegral SCALE)
	FontSizeUnits units ->
	fontDescriptionSetAbsoluteSize fontDesc $ units * fromIntegral SCALE
	pure fontDesc

A FontDescription itself is defined in the pango library. I think pango is the Gnome library dealing with fonts:

https://hackage.haskell.org/package/gi-pango-1.0.16/docs/GI-Pango-Structs-FontDescription.html#t:FontDescription

---

I'm not sure if adding ligature support would be an option to pass to the FontDescription when creating it, or if it is an option that would have to be set on the Terminal itself (or the underlying widget?). It is also possible that ligature support is a feature that is not supported in VTE. (In that case I would suggest creating an issue on the VTE issue tracker.)

If you wanted to spend some time to look into this, I would suggest the following:

• Read through the documentation for gi-vte, gi-gtk, and gi-pango trying to figure out if there are any functions / datatypes dealing with ligature support.
• Do a google search for something like "vte ligature support" or "gtk font ligature" and see if anything good comes up.

If you find some pango or gtk functions that looks promising, but aren't sure how to implement them in Termonad, feel free to post here.

[bts]

@cdepillabout Thanks for your response! Unfortunately it seems like VTE does not currently support ligatures: https://bugzilla.gnome.org/show_bug.cgi?id=781597#c10

[cdepillabout]

@bts Ah, that's unfortunate :-\

I guess I would still suggest opening an issue on the VTE issue tracker (and then posting a link here). At the very least it would let the VTE team know that some people are interested in ligature support in VTE.

[cdepillabout]

There does appear to be an issue on the VTE issue tracker about ligature support, but it doesn't appear to have any progress: https://gitlab.gnome.org/GNOME/vte/-/issues/192