[cairo] Shouldn't Cairo use/offer degrees rather than radians?

Ray Gardener rayg at daylongraphics.com
Mon Jul 10 22:26:18 UTC 2017

One can do cairo_matrix_init right? Just directly set unitary values
to get perfect right-angle rotations?


On 7/10/2017 1:04 PM, David Kastrup wrote:
> cecashon at aol.com writes:
>> Has anyone figured out a good explanation for this? I haven't been
>> able to figure it out. It looks like the problem is tied to only one
>> particular precision point. I don't know why that is. If I change the
>> size of the surface, radius, y-point or even pi I get the same problem
>> point. If I run with valgrind I get a different repetitive problem
>> point.
> Does valgrind link debug libraries in some manner?
>> Maybe on some hardware this doesn't happen?
> That's certainly quite likely since it depends on just what sin/cos do
> on a minuscule scale where different FPUs will quite likely deliver
> different results.
>> I am testing on a Intel 32 bit Atom CPU N270 1.60GHz × 2 with
>> Ubuntu16.04. This is my latest to try to figure out what is happening.
> Compilers may choose to use more floating point precision than specified
> for intermediate results.  That means that different GCC versions and
> different optimization options might change values around.
> For that reason it's important that you don't link with any different
> libraries, even libraries compiled from the same source code.

More information about the cairo mailing list