Hey,

Diego Nicola Barbato <dnbarbato@posteo.de> writes:

[...]

> Apparently there is nothing wrong with the slider.  Instead matrix
> multiplication, which is used under the hood for transformations, seems
> to sometimes produce incorrect results on i686-linux.  I have reported
> this as a separate bug (https://debbugs.gnu.org/41665).

I got this wrong: This issue isn't caused by the Numpy bug, since
Matplotlib doesn't use Numpy for transformations.  Both bugs are caused
by the excess precision of the x87 FPU's floating point registers.

I've attached a patch which makes sure that the C and C++ extensions are
compiled with -ffloat-store.  This doesn't get rid of all possible
rounding errors but it's enough for the slider test to pass.

[...]

Regards,

Diego