Re: Problems with x-, y-coordinates > 8388307

[Damon Chaplin <damon karuna eclipse co uk>]

On Thu, 2008-10-09 at 20:09 +0200, Joachim Geyer wrote:
> Hi all,
> 
> i like to use high coordinate-values (like x(y)-center), but for
> ellipses and lines, coordinates greater than  8388307 do not work for
> me. I have extended the simple-demo.c example to demonstrate the
> problem. If I set the variable "shft" to 8388307.0, I get the
> rectangle, the circle and the text. But with 8388308.0 the circle
> vanishes.

Yes, I can reproduce it. Though it is worse for me - the problem starts
when shft is 32500 here.

It looks like problems with cairo's fixed-point calculations - cairo
uses 24.8 fixed point arithmetic internally so values over +/-2^23 can
cause problems (cairo used to use 16.16, which explains why the problem
happens at ~2^15 for me.)

I added code to GooCanvas to try to work around these limits, but it
looks like it isn't working in this case. I'm not sure where the problem
lies yet.

Damon