[QGIS-trac] Re: [Quantum GIS] #2243: Not accurate extent frame in map overview

[Quantum GIS]

#2243: Not accurate  extent frame in map overview
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        Reporter:  gislab            |         Owner:  nobody       
            Type:  bug               |        Status:  new          
        Priority:  minor: annoyance  |     Milestone:  Version 1.4.0
       Component:  GUI               |       Version:  HEAD         
      Resolution:                    |      Keywords:               
Platform_version:                    |      Platform:  All          
        Must_fix:  No                |   Status_info:  0            
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Comment (by smizuno):

 I believe the extent frame is operating correctly. The main intent of the
 frame is to show what area in the full map data is currently being
 displayed on the main map when zoomed in.

 These are some factors that affect the display position of the rectangle:

 1. Aspect ratio of the Overview vs. main map canvas.

 2. the Overview shows the full extent exactly for all active layers
 (within its aspect ratio), but the zoom full extent actually puts a 5%
 additional buffer so the data are not right on the edge of the map. This
 will cause the rectangle to be outside the overview if both canvases have
 the same aspect ratio.

 3. The small matter of + or - one pixel due to conversion of floating
 point values to integer.

 A better test is to zoom in until the rectangle is the smallest size it
 can be, then positioning the rectangle over a feature on the map. That
 feature will be displayed on the main map.

-- 
Ticket URL: <http://trac.osgeo.org/qgis/ticket/2243#comment:3>
Quantum GIS <http://qgis.org>
Quantum GIS is an Open Source GIS viewer/editor supporting OGR, PostGIS, and GRASS formats