[CM] snd and opengl

[Bill Schottstaedt]

>  Btw, how can I turn it off to revert to the normal FFT display ?

I added a switch named "with-gl" -- set it to #f to revert to the
previous style of spectrogram.

> OTOH I built Snd with just OSS support. Of course it doesn't report any
> xruns, but the traveling cursor is out of sync with the playback. Any
> suggestions ??

This is caused by the "fragments" (i.e. buffers) on the audio card --
Snd is using its current read location to set the cursor location, but
that can be as much as 1/2 second ahead of what's coming out of the
speakers.  You can improve it by using fewer (or smaller?) fragments --
this also improves the responsiveness of the various controls, but
at the cost of clicks.  My "TODO" list includes trying to readback
the fragment settings to fixup this bug; I'll bump it higher
in the queue.