Re: Unidentified subject!

[Kaz Kylheku <kaz ashi footprints net>]

On Mon, 22 Nov 1999 pbg1854@garnet.acns.fsu.edu wrote:

> Don't forget that sometimes X programs are run over a network link.
> Smooth scrolling would be slow as hell if it has to be transfered over
> that, even if it's 100 BaseT ethernet. It doesn't matter *what* you
> use for graphics hardware in this case. And wouldn't double buffering
> be *slower* over a network link? If you use standard X calls, only the
> commands for those calls are transmitted, but if you use a buffer, you
> have to send every pixel in the region over the link, right?

There is no point to doing double buffering for scrolling, because it's just a
bitblt operation, followed by a redraw of some small area. So there may be some
lack of smoothness near the edge away from which the scrolling is taking place.

Double buffering doesn't mean doing image puts over the network; it means that
you draw to a hidden canvas, and then blit from the canvas to the window.  Thus
the user doesn't see the construction of the drawing, just the final result
appearing simultaneously. 

This can be nice if you have a complex drawing, such as dialog box with many
widgets.

Smooth scrolling means scrolling text at a better resolution than the height of
a row of text, for example, scrolling by a single raster line at a time. This
creates an illusion of continous motion, allowing the eye to better track to 
the next line when you are reading.  Some existing X apps have smooth
scrolling: e.g.  ghostview.