[QGIS-trac] Re: [Quantum GIS] #1134: grass toolbox: can't unselect an optional map

[Quantum GIS]

#1134: grass toolbox: can't unselect an optional map
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        Reporter:  hamish                            |         Owner:  rugginoso    
            Type:  defect                            |        Status:  new          
        Priority:  major: does not work as expected  |     Milestone:  Version 1.0.3
       Component:  GRASS                             |       Version:  0.10.0       
      Resolution:                                    |      Keywords:  grass toolbox
Platform_version:  Etch                              |      Platform:  Debian       
        Must_fix:  Yes                               |   Status_info:  0            
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Comment (by hamish):

 Replying to [comment:3 rugginoso]:
 > I can't understand what do you mean about "can't unselect an optional
 map".
 > In the example you provided me (r.cost) you must select a layer into
 each combobox, so the choice to leave empty one of them is incorrect.

 yeah sorry, that's a bad example. in GRASS it is optional but in the QGIS
 wrapper it is not.

 In GRASS you can use specific coordinates, vector map points, or raster
 map pixels for the starting points. Apparently the QGIS wrapper for it
 only offers the chance to use a raster map for that, so it becomes a
 required option in QGIS.

 I'll have to hunt around for one that really shows the behaviour, although
 the effort to minimize module options in the QGIS wrappers may make it
 hard.


 the general idea is this: some modules take optional input maps with a
 default of none. (eg if input data comes from a vector map instead) If you
 use the pulldown menu to select a map for that option there is no way to
 get back to the "none" state.


 Hamish

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Ticket URL: <https://trac.osgeo.org/qgis/ticket/1134#comment:4>
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