[GRASS-dev] Vote for your favorite zoom out

Hamish hamish_nospam at yahoo.com
Mon Oct 2 04:37:04 EDT 2006

Michael Barton wrote:
> Zooming in with a zoom box is pretty straight forward. But zooming out
> is conceptually and computationally somewhat more complex, and is done
> in various ways (or not at all) in other graphics/GIS programs.
> After working off list on various approaches to zooming out with a
> zoom box, I want to give you all several alternative proposals and let
> you vote on them. It gives us a chance to try out the voting
> procedure. I think that we¹d said that we¹d have 2 or 3 days. Since
> it¹s the weekend, I¹ll take votes through Tuesday Arizona time

two points re voting. a) IMO 2-3 days is too short, 4-5 days is a better
compromise between non-stalling & inclusiveness b) I really hope that
any formal voting proceedure doesn't stop anyone who doesn't vote from
speaking up if they have an opinion or new idea.

> Vote for options (I¹m willing to do either 1a/b or 2a/b, and
> personally favor variants 1a or 2a):
> 1a: 1+
> 1b: 0+
> 2a: 1+
> 2b: 0+
> 3:  1-

write in vote: option 4.   (call it 3b if you want)

> 3. The box causes the the display to zoom out, but either does not
> control the amount of zoom out (e.g., region is extended by some set
> amount) or doesn¹t control the region geometry (e.g., the display
> window controls the geometry regardless of the shape of the zoom out
> box).
> Issues: I see no point in going to the trouble of coding a zoom box if
> it doesn¹t give a user control over the region extents (i.e., both the
> amount of zoom and the resulting region geometry). We already have a
> nice quick, 1-click zoom in and zoom out that I¹ve cleaned up a bit
> more over what is now in the cvs.

4. No zoom out by box. Zoom out click (right click from zoom-in?)
zooms out by a factor of 2 or sqrt(2) [or something in between].
New region is centered on location of the click. bounds change but
resolution is preserved.

A couple problems with zoom out by box:

 - it's friggin confusing for us to decide what it means, think of how
the user will cope.

 - it's easy to try and single-click to zoom out, but actually draw a
1x1 pixel box, and zoom out like mad. I *always* do this when using
software with zoom-out by box and it drives me nuts.

 - conceptually you are drawing a box on the window glass, and ignoring
what's behind the glass [ie imagine what the new map will look like in
real time, then draw your box on that mental projection after rescaling
and placing the current display map in your head...]. This is a totally
different place to put your brain vs. zooming in where you are using a
direct god's eye view. When quickly zooming in+out to get just the right
area this duality makes your head spin, or at least slow you down when
you jump the groove.

I can see the advantage of using a zoom-out box if you want to ever so
slightly zoom out, but the click to zoom-out by sqrt(2), and redoing a
zoom-in box ain't so bad.

I argue for the right click to unzoom when in zoom-in mode for speed
to final result. (probably in addition to a formal zoom-out button)


- left click zooms in by 2 or sqrt(2) immediately
- left click drag zooms in to box, highlights box but doesn't zoom yet
   (gives you a chance to try again)
- middle click accepts highlighted zoom-in box & redraws
- left or right button click while highlight box is up cancels the box
   and does nothing to the zoom (escape route)
  left click drag draws a new box
- right click zooms out by 2 or sqrt(2)

now you may be thinking this is as confusing as the current xmon
prompts, but those not in the know can still click to zoom in/out.

keyboard click for zoom-out ain't so bad for 1 button applers.
keyboard clicks for zoom-in box is not intuitive for applers, but not
 disabling as single click to zoom still works. but it kinda sucks.
 ("gis requires at least 3 buttons. spend the $10. not long ago GIS
   digitizing pallets were 4-12 buttons")
 Photoshop's authors probably have the same UI nightmares on Mac.

without getting into platform wars, I always saw the single button mac
mouse more as a way to force developers to come up with easy to use
interfaces (like now), but much less useful for a user. We have 5
fingers after all, and know how to use them to do different things.
All users win a lot in the forced good design with a single button mac,
but the power user is slowed down some. This doesn't mean a 3 button
mouse is bad to use!


More information about the grass-dev mailing list