[QGIS-trac] [Quantum GIS] #2542: field calculator default behaviour

[Quantum GIS]

#2542: field calculator default behaviour
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   Reporter:  best              |              Owner:  nobody       
       Type:  enhancement       |             Status:  new          
   Priority:  minor: annoyance  |          Milestone:  Version 1.5.0
  Component:  Vectors           |            Version:  1.4.0        
   Keywords:  field calculator  |   Platform_version:               
   Platform:  All               |           Must_fix:  No           
Status_info:  0                 |  
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 Thank you for the field calculator it is a very welcome feature!
 However its default behaviour (checkbox settings) is to update '''all'''
 records in the first '''existing''' field. This applies to QGIS 1.4.0-2.8
 (OpenSuse).[[BR]]
 To prevent users from corrupting their data I would expect it the other
 way round: update only selected records and ask for a new field.

 == Explanation ==
  * Most of the time I am using the field calculator, I want to update only
 selected records (graphical or logical selection). So I have to take extra
 care to check ''only update selected features''. When I forget to do so,
 my data already being in the target field are gone. On the other hand if I
 want to update all records and the default would be ''only update selected
 features'' all I have to do is redoing the calculation after unchecking
 ''only update selected features''.[[BR]]

  * The first existing field normally is an ID field. You do not want to
 update this field! But if you do not take extra care you do so. If
 ''update existing field'' would be unchecked the user has to do something
 in order to execute the calcualtion: either check ''update existing
 field'' and choose the field or enter a new field. Thus the risk of data
 corruption by accident is minimized.[[BR]]

 I am totally aware that discarding the changes keeps the data as they are.
 But it is annoying to stop the edit mode, discard all(!) changes and redo
 all I did when I realize I made a mistake (if I realize!).

 == Proposal ==
  * If a selection exists on the table check ''only update selected
 features'' by default.
  * Uncheck ''update exisiting field'' by default.

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Ticket URL: <https://trac.osgeo.org/qgis/ticket/2542>
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