You are not seeing thing like "we're enabling system cairo here ..." directly in ebuild because it is done inside mozcoreconf-2.eclass which inherited by mozconfig-3.eclass which inherited by firefox ebuild. Inheriting eclass can be thought of as pretty close equavivalent of using #include directive in C.
(In reply to comment #53) sources. gentoo. org/cgi- bin/viewvc. cgi/gentoo- x86/www- client/ firefox/ 19.0.2. ebuild? view=markup it seems that the use of system-cairo has
> Reading
> http://
> firefox-
> been dropped. Which is a shame.
You are not seeing thing like "we're enabling system cairo here ..." directly in ebuild because it is done inside mozcoreconf- 2.eclass which inherited by mozconfig-3.eclass which inherited by firefox ebuild. Inheriting eclass can be thought of as pretty close equavivalent of using #include directive in C.