(No version information available, might only be in SVN)
Matrices are used throughout cairo to convert between different coordinate spaces.
$xx
= 1.0
[, float $yx
= 0.0
[, float $xy
= 0.0
[, float $yy
= 1.0
[, float $x0
= 0.0
[, float $y0
= 0.0
]]]]]] )