Created attachment 30874 [details] [review]
Stop cairo requiring specific versions of libpng
Cairo configure.ac specifically detects libpng versions, thus attempts to release new versions of libpng (post 1.2) are foiled by the failure of cairo to even configure.
The attached file fixes the problem.
1.4.0 has been tested against cairo and compiles correctly.
This has been fixed in cairo master in commit
If you can check whether the fix works for you that would be great, and if it doesn't please provide some OS info in your bug report. If it does we can push the fix into the 1.8 branch for the next stable update.
(In reply to comment #1)
I tested it (the commit diff) and it worked. I applied it to configure, not configure.ac, as gentoo loads a distribution package (the source with autogen.sh already run). The result did, indeed, find libpng14
Anyway by visual examination it will be equivalent to my version.
You can repro anywhere by installing libpng-1.4.0beta88 (or, probably, any 1.4.0 beta) and *removing* any older libpng libraries. If you don't remove the libraries (the normal situation) the problem is undetectable because configure finds the old library but then the build uses the new, 1.4, png.h header (and the new library.)
Cherry-picked and pushed to the 1.8 branch, so it'll be fixed in 1.8.10 when that's released. Cheers.