[GRASS-dev] Re: [GRASS GIS] #295: region corrupted

[Michael Barton]

On Dec 17, 2008, at 12:22 AM, <grass-dev-request at lists.osgeo.org> wrote:

> Date: Wed, 17 Dec 2008 07:22:45 -0000
> From: "GRASS GIS" <trac at osgeo.org>
> Subject: [GRASS-dev] Re: [GRASS GIS] #295: region corrupted
> To: undisclosed-recipients:;
> Message-ID: <051.2301d585497eab3a94c92ac263194240 at osgeo.org>
> Content-Type: text/plain; charset="utf-8"
>
> #295: region corrupted
> ----------------------- 
> +----------------------------------------------------
>  Reporter:  msieczka  |       Owner:  grass-dev at lists.osgeo.org
>      Type:  defect    |      Status:  new
>  Priority:  critical  |   Milestone:  6.4.0
> Component:  wxGUI     |     Version:  svn-develbranch6
> Resolution:            |    Keywords:
>  Platform:  All       |         Cpu:  All
> ----------------------- 
> +----------------------------------------------------
> Comment (by hamish):
>
> ok, so it is a matter of expectations.
>
> how to improve the wording?
>
>  * I think all the "Zoom display to ..." menu items can stay as-is,  
> as it
> is not as critical if the display region is slightly askew. -- it's  
> just a
> visual thing. So vague language is ok here.
>
>  * My suggestion to solve this ticket is to reword "'''Set  
> computational
> region extents to match display'''". It is critical to have the
> computational region set cleanly for computations, and g.region -a is
> needed to avoid sloppy regions set from the display. So crisp  
> language is
> needed to explain this.
>
> Replace "to match" with "from"? that makes it more technically  
> correct,
> but still doesn't address the user expectation issue very well.
> Replace "Set" with "Align"? That puts forward the idea that the two  
> grids
> are still somewhat independent.
>
> how about: "Align computational region to current display"?
>

This sounds fine. I need to look at the code again, but I'm pretty  
sure that most of the variance reported here is in the "Zoom display  
to computational region..." step. The display is designed to fit in  
the window regardless of whether the computational region has the same  
proportions as the window or not. The computational region can be seen  
with a colored rectangle that can be turned on or off.

When you 'Zoom computational region to display...', the region extents  
are actually set to match the display. I suppose there could be a  
pixel/grid cell difference, but the algorithm simply takes the display  
extents in real world coordinates and puts those into g.region.

If "align" seems a more accurate way to phrase this, then I'm in favor  
of it.

Michael