[GRASS5] Driver Update

[Markus Neteler]

On Wed, Apr 25, 2001 at 05:48:53PM +0100, Glynn Clements wrote:
> 
> Markus Neteler wrote:
> 
> > Maybe it is a KDE2/Xfree4.0.2 related problem. In past the backing store
> > problem was odd in GRASS 5, this was fixed by Eric Miller. This little
> > problem described above doesn't harm me, I just wanted to report it.
> 
> This may have been fixed by my most recent commit. Now:
> 
> 1. backing_store is always set to NotUseful
> 
> 2. A Pixmap is always created.
> 
> 3. All rendering is performed on the Pixmap.
> 
> 4. The Pixmap is made the window's background pixmap, so there is no
> need to handle Expose events. A RESPOND command (sent by
> R_stabilize()) will force an update using XClearArea.

I see. BTW: Now the monitor behaviour is different than before: The image
will be displayed only when it is complete. Of course the same result
as if it would be build up continuously. However, with larger datasets
(and slow machines) users may become nervous why nothing is seen for
a while. I am not sure if this "wait - then display-at-once" is better
than "draw line-by-line" is better (however, you may have reasons for
this change).

> BTW: Are the "Panel" operations actually used by anything? Neither
> CELL nor PNGdriver implement them, and the XDRIVER implementation
> looks suspicious. Is there any way to test them?
Sorry, no idea about this.
The progmangrass50.pdf tells us (chapter23.tex = "28 Writing a Graphics
Driver"):

"28.3.6 Panels 
The following routines cooperate to save and restore sections of the display
screen."
[...]

A "find" didn't find it in use anywhere else.

This manual is in CVS
cvs -z3 co progmangrass50

in case you want to update above section.

Markus

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