[cairo] API Shakeup: default matrix (axes and origin)

[Øyvind Kolås]

On Mon, 21 Feb 2005 10:28:02 -0500, Carl Worth <cworth at cworth.org> wrote:
>    **snipped away stuff about initial user space unit**

Since we're already doing a shakeup on the API and drawing model
of cairo I think we also should reconsider the axes, and origin
used by cairo.

Doing as postscript and having the origin in the lower left corner
with the y axis extending upwards, provides a coordinate system that
is simpler for mathematicians to work with, since then they would
be drawing in the "positive quadrant".

Having the y axis extending upwards also has the added benefit of
matching the coordinate system used when describing fonts.

The regular computer graphics way of describing a coordinate system
only has the advantage of familiarity for people that are familiar
with the memory layout used for linear frame buffers.

An even more extreme option, would be to place the origin in the
middle of the surface. This will make some vectorial drawing simpler,
but I have not put a large amount of thought into it.

/Øyvind K./pippin

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