Slow rendering when GC.line_style = LineOnOffDash

[Po Lu]

"Farrington, Paul" <Paul.Farrington at fisglobal.com> writes:

> We’ve noticed that XDrawRectangle where the GC.line_style is
> LineOnOffDash has gotten slower in recent X Server releases. We’ve
> observed this on both Linux RH8 and FBSD 11.4 and above. There are two
> sample programs pasted below, one which draws 5 rectangles with
> LineSolid and one which draws 5 rectangles with LineOnOffDash. There
> is also a makefile for RH8. Running the two programs with an X Server
> version 1.18.4, both programs render the rectangles instantly. But in
> X Server version 1.20.8 or more obviously 1.20.14, rendering the
> dashed line rectangles is much slower. You can watch them being drawn
> on the screen, whereas the solid line version still renders instantly.

This information doesn't help unless you tell us:

  - which graphics driver (xf86-video-foo) you are using.
  - what kind of acceleration it is using (i.e. EXA, UXA, SNA, or
    Glamor.)