[comp.sys.hp] Double buffering in Starbase/X11 combined mode.

beshers@division.cs.columbia.edu (Clifford Beshers) (09/11/90)

Using a Turbo SRX, with X11R4 in combined mode, 12/12 planes
double buffered, I ran two copies of an animation on the same
display.  When a process has the input focus, it runs smoothly,
but the other flickers, because the double buffering is out of sync.

Fortunately, the manual documents this.  Unfortunately, it seems
to suggest that there is no cure.  Does anyone know otherwise?
--
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Clifford Beshers
450 Computer Science Department
Columbia University
New York, NY 10027
beshers@cs.columbia.edu

tomg@hpcvlx.cv.hp.com (Thomas J. Gilg) (09/11/90)

> Using a Turbo SRX, with X11R4 in combined mode, 12/12 planes
> double buffered, I ran two copies of an animation on the same
> display.  When a process has the input focus, it runs smoothly,
> but the other flickers, because the double buffering is out of sync.

The TSRX only has one hardware colormap, so you're seeing one of your
two applications controlling it, and the other being ignored.  There
is no way to avoid this for multiple unrelated clients.  It is possible
for one client to have multiple DB output windows however.

BTW - the new Turbo VRX (hp98735/98736) finally supports multiple (~14)
hardware colormaps.

Thomas Gilg
tomg@cv.hp.com

stroyan@hpfcso.HP.COM (Mike Stroyan) (09/12/90)

> Using a Turbo SRX, with X11R4 in combined mode, 12/12 planes
> double buffered, I ran two copies of an animation on the same
> display.  When a process has the input focus, it runs smoothly,
> but the other flickers, because the double buffering is out of sync.
> 
> Fortunately, the manual documents this.  Unfortunately, it seems
> to suggest that there is no cure.  Does anyone know otherwise?

There are a couple of possible cures.  One involves effort and the
other involves money.

You could modify the animation programs to communicate between
each other and synchronize their dbuffer_switch operations.
System V semaphores would make a good communication channel.

You could buy a Turbo VRX, which supports multiple simultaneous
colormaps and double buffering states.

Mike Stroyan, mike_stroyan@fc.hp.com