tl;dr: cairo-sphinx is on the chopping block for 1.18.0; if you use it, please tell us how you're using it, so we can actually document it.

In order to reduce the amount of differences between upstream and downstream Cairo builds, I have recently enabled the tee surface, which is currently used by Firefox.

With the tee surface enabled, cairo-sphinx is also getting built, which produced a build failure when building Cairo as a static library: https://gitlab.freedesktop.org/cairo/cairo/-/issues/791

I tried to fix this, but ended up making a mess; luckily, Uli proposed another fix that always builds cairo-sphinx as a shared library: https://gitlab.freedesktop.org/cairo/cairo/-/merge_requests/509

The problem is, though, that we have no way of knowing if the fix is working, because there are no instructions on how to use cairo-sphinx; the code was committed in 2009 and has not changed in the past 14 years, so we don't even know if it has been working properly in that time. The tee surface has always been disabled by default, and only downstreams building Firefox with a system copy of Cairo would actually exercise the build.

So now is the time: if you use, or used, cairo-sphinx, please tell us **how**, so we can at least add a README file in there. Otherwise, we should remove it: https://gitlab.freedesktop.org/cairo/cairo/-/merge_requests/510

Ciao,

 Emmanuele.