This changes the buildlink3.mk files to use an include guard for the
recursive include. The use of BUILDLINK_DEPTH, BUILDLINK_DEPENDS,
BUILDLINK_PACKAGES and BUILDLINK_ORDER is handled by a single new
variable BUILDLINK_TREE. Each buildlink3.mk file adds a pair of
enter/exit marker, which can be used to reconstruct the tree and
to determine first level includes. Avoiding := for large variables
(BUILDLINK_ORDER) speeds up parse time as += has linear complexity.
The include guard reduces system time by avoiding reading files over and
over again. For complex packages this reduces both %user and %sys time to
half of the former time.
From pkgsrc-wip, packaged by Paulo Matias.
Anti-Grain Geometry (AGG) is an Open Source, free of charge
graphic library, written in industrially standard C++. AGG
doesn't depend on any graphic API or technology. Basically,
you can think of AGG as of a rendering engine that produces
pixel images in memory from some vectorial data.
