[GRASS5] XDRIVER and redraw - suggestion

[Glynn Clements]

Markus Neteler wrote:

> while on the one hand the redraw function of XDRIVER is nice,
> it can become rather annoying with large maps (say, 500MB-1GB
> remote sensing data).
> 
> What about following suggestion: the XDRIVER reads the environmental
> variable
> XDRIVER_MAX_NREDRAW
> which defines the maximal number of maps kept in the monitor
> list. If not defined, no limitation, if defined, the user
> can specify the maximum numbers of maps to be redrawn. Inthis
> case the XDRIVER forgets about the older drawn maps.
> 
> It would be nice to have this optional variable.

Note that XDRIVER doesn't know anything about "maps"; it just has a
list of commands which it runs whenever the monitor is resized. 
Determining which commands constitute a "map" and which don't isn't
straightforward; "d.rast" isn't the only command which draws maps.

Ultimately the XDRIVER resize kludge is just a quick workaround to
compensate for the absence of an interactive UI. Realistically, the
monitors should just be dumb graphic "devices"; state management
belongs elsewhere (the fact that, currently, there isn't a suitable
"elsewhere" doesn't doesn't change that).

If the command list is getting too long, use "d.erase".

-- 
Glynn Clements <glynn.clements at virgin.net>