Arch Linux

FlowIt

Member

Registered: 2014-10-25

Posts: 243

Firefox: Fonts wider on wayland and/or higher vertical resolution

I upgraded from a 16:9 screen (1920x1080 resolution) to a 16:10 screen (1920x1200 resolution). At the same time I also switched from X11 windowing to wayland windowing, in particular from i3 to sway.

When using firefox, I noticed that the text is now wider, showing fewer characters on a line in comparison to the old screen. Fonts and settings are identical. For a quick check I also tried vim and found out, that inside the editor I can now have 10 characters more on a single line. I find that a bit surprising, since the X resolution stayed the same.

Does anybody have an idea what to check?

V1del

Forum Moderator

Registered: 2012-10-16

Posts: 25,223

Re: Firefox: Fonts wider on wayland and/or higher vertical resolution

The magic keyword is DPI, on Xorg it's hard defaulted to 96 on wayland it will generally be calculated based on what the monitor reports (also "wayland" doesn't exist, which compositor is this?) .  https://wiki.archlinux.org/title/HiDPI

FlowIt

Member

Registered: 2014-10-25

Posts: 243

Re: Firefox: Fonts wider on wayland and/or higher vertical resolution

The compositor is sway.

I found this wiki article as well, but it wasn't able to solve my issue with its help.
Modifying the scaling factor seems the wrong choice, because it scales both the x and y resolution. It's hard to measure but it somehow feels that only the X resolution is off while the Y resolution is perfectly fine.

And again the comparison with vim: swaymsg -t get_outputs reports a scaling factor of 1.0. Setting ui.textScaleFactor to 100 in firefox does not change the looks at all. It's definitely not a wayland issue then but firefox specific.

seth

Member

From: Won't reply 2 private help req

Registered: 2012-09-03

Posts: 75,979

Re: Firefox: Fonts wider on wayland and/or higher vertical resolution

It's definitely not a wayland issue then but firefox specific.

Ie. you've tested the behavior on an i3/X11 session and the same behavior exists there?
Also

And again the comparison with vim

For a quick check I also tried vim and found out, that inside the editor I can now have 10 characters more on a single line.

rather suggests that "vim" (ie. the font in either gvim or your TE) is affected as well - contraditing the FF theory.

Fonts are vector graphics that get rastered into pixels at a really small absolute dimension, so minor absolute changes have large relative impact.
The actual font size (odd, even, decimal), the hinting configuration, the rasterizer (notably harfbuzz vs. freetype) play into that and it's eg. common that, at small sizes, the appearance between odd and even point sizes varies between wide and narrow.

So:
- test the behavior on X11
- record the physical dimensions of both monitors (ie. how many mm is the physical panel wide and high) - the DPI is relevant, how many pixels you have total is not.
- record the actual testcases (font/s, sizes, what is "vim" itr, gvim or some terminal window)
- to get everyone on the same page, link some screenshots.

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