Created attachment 6744 configure.ac.in patch Patch attached.
Looks OK at a glance. The only thing I'd change is to use AS_MSG_ERROR() rather than echo/exit commands, but it's not really important, and I didn't look to see which way the existing checks do it.
I just pulled it from xfce4-notifyd as gaston suggested.
(In reply to Igor from comment #2) > I just pulled it from xfce4-notifyd as gaston suggested. It's probably fine, I suppose most shells probably have some kind of builtins or separate utilities for `echo` and `exit`, it just seems a little nicer using the Autoconf macros to be sure. No biggie, I'll look at it closer when I merge this.
Igor referenced this bugreport in commit 595b3a572cea618d2fa87506860ab3d01fddd0f6 Check for exo-csource in maintainer mode (Bug #12719) https://git.xfce.org/apps/mousepad/commit?id=595b3a572cea618d2fa87506860ab3d01fddd0f6
LGTM, thanks.
Thanks for merging! I'd completely forgotten about this patch and was so surprised seeing I committed something. ;)