#1105093 fvwm: should filter out non-printable characters for the window title

Package:
fvwm
Source:
fvwm
Description:
F(?) Virtual Window Manager
Submitter:
Vincent Lefevre
Date:
2025-06-01 00:03:02 UTC
Severity:
normal
Tags:
#1105093#5
Date:
2025-05-10 23:39:33 UTC
From:
To:
Fvwm should filter out the non-printable characters for the window
title.

The issue can be reproduced with

  xmessage -geometry 400x100 -title "$(printf "\u200E ABC")" Test

(or with gxmessage). Due to the U+200E LEFT-TO-RIGHT MARK character,
I get some strange glyph before "ABC". Without the space before "ABC",
this glyph appears partly over the "A".

Note: I first saw this issue with

https://community-imdb.sprinklr.com/conversations/data-issues-policy-discussions/announcement-contribution-form-update/681b76ab20d5b71fad32eac8

whose title starts with the U+200E LEFT-TO-RIGHT MARK character, and
I was wondering about the cause of the display issue.
#1105093#10
Date:
2025-05-31 19:05:08 UTC
From:
To:
This really isn't something I think fvwm should do, as fvwm doesn't
really know if characters are in a user's fonts or not, this is all
done via libxft and fallback fonts.

This works fine on my system because I have fallback fonts with the
correct characters. You should consider using xft fonts and letting
them fallback to fonts that have the desired unicode characters to
avoid the issue.

Also, I would also suggest considering migrating to fvwm3, fvwm
(version 2) is no longer developed and no new features will be added.

xmessage -geometry 400x100 -title "$(printf "\u200E ABC")" Test

jaimos
#1105093#17
Date:
2025-05-31 20:11:55 UTC
From:
To:
Bad copy and paste, I meant to provide a link on how to migrate from
fvwm2 to fvwm3.

https://github.com/fvwmorg/fvwm3/discussions/878
#1105093#22
Date:
2025-05-31 23:55:06 UTC
From:
To:
Non-printable characters should never be present in any font,
as they are not printable.
#1105093#27
Date:
2025-05-31 23:56:08 UTC
From:
To:
Note that there is nothing about the replacement of FvwmM4.