[cairo] problem with downscaling images and destination coordinate spaces

[Bill Spitzak]

Behdad Esfahbod wrote:
> On Tue, 2007-05-29 at 14:14 -0400, Daniel Amelang wrote:
>> On 5/28/07, Vladimir Vukicevic <vladimir at pobox.com> wrote:
>>> The problem seems to be that pixman transformation matrices are 16.16
>>> fixed; thus the scaled offsets end up overflowing.
>> Carl has been threatening to make cairo fixeds 24.8. Maybe pixman
>> fixeds should also be made 24.8 when that happens.
>>
>> Dan Amelang
> 
> There should be a better fix possible in this case.  Not sure how
> exactly, maybe extract the integer part of the offset into a full int or
> something.

That may work very well, because a flag could also be kept that 
indicates whether the remaining matrix is the identity or not, and avoid 
the matrix mulitply in those cases.