[cello-devel] Scroll, baby, scroll!

Kenny Tilton ktilton at nyc.rr.com
Thu Mar 11 13:28:45 UTC 2004

Kenny Tilton wrote:

> Well it took a fundamental change to Cello rendering, a fix to Cells, 
> and thank god for gl-bitmap, but we now have scrolling of textures and 
> pixels in Cello, as well as clipping of pixels. It's just a scroll 
> pane which responds to arrow and pagedown/up/home/end keys, but the 
> scroll bars are just sliders, should roll over with an hours work.
> Gonna treat myself to a workout, then see if I can jazz up the Cello 
> website on common-lisp.net. 

Damn, just flailing away on the elliptical I realized sub-widgets would 
still execute gl-raster-pos calls and knock themselves out of 
consideration by OpenGL. So if a text widget scrolls its origin (on the 
left, at the type baseline) one pixel out of the clipping plane, poof!, 
the whole thing disappears.

So there is more work to do, but at least the technology is getting 
understood and seems adequate to the task. I just have to make Cello 
play by their rules. And I haven't even explored using gl-view-port as a 
clipping weapon, or my original idea of a separate glutWindow or 
glutLayer. I am holding off on the glut-based solutions to keep things 
simpler and avoid glut dependencies Just In Case we ever need to dump 



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