Character rendering broken with varying word lengths combined with wrapping

[Lyude]

Describe the bug
If you have wrapping enabled in neovim-gtk (:set wrap) and you have a long string of text which contains words of varying lengths (such as the string "foo ba " repeated until wrapping starts), some of the words don't appear to actually render. Interestingly enough, the only words that don't render are ones which are shorter than the longest word in the string.

Technical information (please complete the following information):

• OS: Fedora 33 x86_64
• Neovim version: master
• Neovim-Gtk build version: https://copr.fedorainfracloud.org/coprs/yalter/neovim-gtk/build/1650863/

Some other info that might help:

• Pango version: 1.47.0
• GTK version: 3.24.23

[Lyude]

Heh, moments after filing this issue I happened to notice something else: it's not just word wrapping, the problem seems to happen if there's any non-ASCII glyphs being displayed on the same line ("→foo ba foo" by itself exhibits the same issue):

[theHamsta]

Possible duplicate of #254 . I have the same issue since updating to Ubuntu 20.10 and thus to a newer pango version. Would really love having this solved.

[Lyude]

Hm, ironically I had just finished teaching myself rust (I've done plenty of C programming, but rust is new to me!) and was about to start debugging this and come up with a fix, and then I noticed after updating my system today I'm not seeing the issue anymore. It looks like maybe this was a regression with pango or something? Unfortunately I'm not quite sure what updated to fix this, fwiw: I'm now on pango 1.48.0-1.fc33, gtk3 3.24.24-1.fc33.

@theHamsta btw ^

[Lyude]

Ah-nevermind, just managed to reproduce it. Looking to see if I can figure out the fix for this

[theHamsta]

😄 Just recompiled with latest master of pango, and I'm also still seeing this issue.

[Lyude]

Also dear neovim-gtk maintainer - if you can get to this first I'd recommend it, I'm definitely not that familiar with this codebase (and don't have a whole ton of time on my hands) so it might take me a while to figure out the problem here.

I have figured out one thing at least, which is that it was 279bd5256b17ed68d50fbaaf7df60f189de33c96 ("itemize: Work around gtk2 brokenness") in pango that caused this breakage

[theHamsta]

Btw. I am not a maintainer. But your info may be interesting for @daa84