[OpenLayers-Trac] Re: [OpenLayers] #1894: Digitizing donut-like polygons

[OpenLayers]

#1894: Digitizing donut-like polygons
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 Reporter:  jachym           |       Owner:  tschaub     
     Type:  feature          |      Status:  assigned    
 Priority:  minor            |   Milestone:  2.11 Release
Component:  Handler.Polygon  |     Version:  SVN         
 Keywords:  Polygon          |       State:  Review      
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Changes (by tschaub):

  * state:  => Review


Comment:

 Latest patch adds interior ring digitizing to the Polygon handler.  The
 [http://dev.openlayers.org/sandbox/tschaub/donut/examples/donut.html
 example] demonstrates its use.  Some basic topology rules are enforced
 while digitizing interior rings:

  * All nodes of interior rings must intersect existing polygon
  * Newly added interior rings must have non-zero area
  * Newly added interior ring cannot intersect any existing interior rings
  * Newly added interior ring cannot contain any existing interior rings

 The first rule is enforced while digitizing.  The others are enforced when
 ring digitizing is complete.  This allows the creation of more complex
 rings (like a C shaped ring that nearly encloses another interior ring)
 while disallowing the most egregious of invalid geometries (as with
 exterior rings, bow-tie rings are still allowed).

 The example works and tests pass in FF 3.6, Chrome 6, and IE 6.  Thanks
 for any review.

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Ticket URL: <http://trac.openlayers.org/ticket/1894#comment:3>
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