[GRASS-dev] Re: gis.m zooming: 2 new bugs

[Maciej Sieczka]

Michael Barton wrote:
> Maciej has the right idea. Let's start with how the zoom out box works in
> the "normal" context and deal with the "abnormal" context later.
> 
> The zoom out box DOES respect the form of the box drawn... BUT not in the
> same way that the zoom in box does.

> So how is this actually used in practice? Say you have a regional map,
> zoomed in to a city. You'd like to zoom out to the larger region and have
> the city end up in the upper left corner of your map. Create a zoom out box
> of the size you want--that is, such that the current display will fit
> inside--in the upper left corner of your display. The currently displayed
> map, with the city in the center, will appear within the area of the zoom
> out box.

OK, now I understand how it works. Questions:

Why did you implement it this way? Other GIS software working the same?

I checked the box-zoom-out in QGIS and UDIG - neither behaves the way
gis.m does. Of course, this is not an ultimate argument. But I'm
wondering why you decided for an IMO counter-intuitive, non-standard
(to my limited experience) solution?

I can explain why IMO counter-intuitive: when I draw a box (no matter
if zoom-out or zoom-in one) I (naturaly, I think) expect the objects
within this box to be in the center of display in a result. With gis.m
for box-zoom-out this will only happen if I over a center of the
canvas. If I draw the zoom box in eg. the top left corner, the
resulting region will be still centered on the former center, not on
the center of my zoom-box. Also, I don't know how to enforce the region
shape as I wish.

It took me 3 days to understand how box-zoom-out in gis.m works. Only
thanks to your long emails and patience. I admit my attitude was biased
by what I expected, but I believe other Grass users might be biased the
same way and get puzzled or frustrated as I did. I believe the "normal"
way (eg. QGIS and UDIG) of box-zoom-out is as good as your current
approach in terms of browsing maps, but, which is even more important
for Grass GIS in the *restricted* zoom mode, the "normal" way lets the
user control the region shape and extent precisely. I'm sorry, but the
way your box-zoom-out works I'm really not able to control the region
extent and shape. Which I believe is a defect, epsecially in the
restricted zoom mode, which is mainly about setting the region in a
predictable way.

Would you be willing to implement it the way I mean?

Moritz, what do you think. Guys?

Maciek