X11 – Command to Find Font Used by X Client Window

command linefontsx11

I'm trying to find a command that will report what font a given X window is configured to use. Does such a command exist?

Looking through these tools I did not see an option that would give me this:

  • xwininfo
  • xdpyinfo
  • xprop
  • xlsclient

Looking through the output of lsof I see font files that appear to be in use, however it's not clear which ones, if any, are actually being used by a given window.

Example

$ lsof |grep gnome-ter|grep font | head -8
gnome-ter  3282      saml  mem       REG              253,0    223040    1180775 /usr/lib64/libfontconfig.so.1.4.4
gnome-ter  3282      saml  mem       REG              253,0   3656228    1588238 /usr/share/fonts/un-core/UnDotum.ttf
gnome-ter  3282      saml  mem       REG              253,0    585272     266781 /usr/share/fonts/gnu-free/FreeSans.ttf
gnome-ter  3282      saml  mem       REG              253,0    323284    1447753 /usr/share/fonts/dejavu/DejaVuSansMono.ttf
gnome-ter  3282      saml  mem       REG              253,0    190240    1588229 /usr/share/fonts/paktype-naqsh/PakType_Naqsh.ttf
gnome-ter  3282      saml  mem       REG              253,0    683528    1447770 /usr/share/fonts/dejavu/DejaVuSans.ttf
gnome-ter  3282      saml  mem       REG              253,2     42144   10488291 /home/saml/.fonts/ProggyCleanSZBP.ttf
gnome-ter  3282      saml  mem       REG              253,0     15504    1966923 /var/cache/fontconfig/87f5e051180a7a75f16eb6fe7dbd3749-le64.cache-3

To be clear, I'm not interested in this solution, titled: How to check which font the system uses?:

$ gconftool-2 --get /apps/gnome-terminal/global/profile_list
[Default,Profile0]

$ gconftool-2 --get /apps/gnome-terminal/profiles/Default/font
Monospace 12
$ gconftool-2 --get /apps/gnome-terminal/profiles/Profile0/font
TakaoMincho Bold 36

I want to determine this information via X if possible.

References

Best Answer

Most modern applications, including all Gtk (→ GNOME) and Qt (→ KDE) applications, use xft, which performs the rendering client-side and sends an image to the server. (Possibly via the XRender extension, but it's an image that gets sent for rendering, not text). So for these applications the X server has no notion of fonts. You can't do any better than checking whether the application has (had) the font file opened.

Even for old-fashioned applications that use server-side fonts, I don't think there's a way in Xlib to query which fonts another client is using.

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