[mapguide-trac] #1481: getselectedfeatures should use more efficient centroid processing

[MapGuide Open Source]

#1481: getselectedfeatures should use more efficient centroid processing
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   Reporter:  jng          |       Owner:  jng  
       Type:  defect       |      Status:  new  
   Priority:  low          |   Milestone:  2.2  
  Component:  AJAX Viewer  |     Version:  2.2.0
   Severity:  major        |    Keywords:       
External_id:               |  
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 The current getselectedfeatures.aspx/php/jsp uses MgGeometry.GetCentroid()
 to calculate the zoom location.

 It turns out GetCentroid() does a full scan of the geometry's WKT.

 For geometries with an absurd amount of vertices, this is a woefully
 inefficient method of calculating the centroid.

 Since the purpose of this centroid is to be the zoom location, we don't
 exactly require a *precise* zoom location. Something approximate should
 suffice. So the centroid processing should change from this:

 {{{
 MgCoordinate pt = geom.Centroid.Coordinate
 zoom.X = pt.X;
 zoom.Y = pt.Y;
 }}}
 to this:
 {{{
 MgEnvelope env = geom.Envelope();
 MgCoordinate ll = env.GetLowerLeftCoordinate();
 MgCoordinate ur = env.GetUpperRightCoordinate();
 zoom.X = (ur.X + ll.X) / 2;
 zoom.Y = (ur.Y + ll.Y) / 2;
 }}}

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Ticket URL: <http://trac.osgeo.org/mapguide/ticket/1481>
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