= !MapGuide RFC 38 - GETDYNAMICMAPOVERLAYIMAGE Enhancements for Selection =

This page contains an change request (RFC) for the !MapGuide Open Source project.  
More !MapGuide RFCs can be found on the [wiki:MapGuideRfcs RFCs] page.


== Status == 
 
||RFC Template Version||(1.0)|| 
||Submission Date||Oct 2 15:40:00 2007 ||
||Last Modified||Trevor Wekel [[Timestamp]]||
||Author||Trevor Wekel||
||RFC Status||draft||
||Implementation Status||pending||
||Proposed Milestone||2.0||
||Assigned PSC guide(s)||||
||'''Voting History'''||Oct 9, 2007||
||+1|| ||
||+0|| ||
||-0|| ||
||-1|| ||
 
== Overview ==

Enhance the GETDYNAMICMAPOVERLAYIMAGE HTTP API to allow the selection and overlay images to be rendered as separate images.

== Motivation ==

Currently, !MapGuide renders the selection and the overlay image as a single image.  This requires all untiled layers to be redrawn whenever the selection is changed.  This is an inefficient use of server-side rendering resources and it reduces multi-user performance for untiled maps.  

== Proposed Solution ==

Add an additional parameter BEHAVIOR to the existing GETDYNAMICMAPOVERLAYIMAGE. Increase the VERSION to 2.0.0 and deprecate the existing KEEPSELECTION parameter for the new version of the API.  BEHAVIOR is a bitmask with the following values:

{{{
  RenderSelection = 1
  RenderLayers = 2
  KeepSelection = 4
}}}

Add an additional signature for !MgRenderingService.!RenderDynamicMapOverlay that includes the behavior parameter:

{{{
  MgByteReader* RenderDynamicOverlay(MgMap* map, MgSelection* selection, CREFSTRING format, INT32 behavior);
}}}

Update the existing !WebLayout based ajax viewer to use the new API.

== Implications ==

Since this is a new version of the HTTP request and a new signature for RenderDynamicMapOverlay, compatibility with existing clients/scripts is maintained.  The behavior parameter encapsulates the current "keepSelection" functionality so the existing RenderDynamicOverlay methods could be deprecated in a future release.

== Test Plan ==

Ensure that existing clients continue to function as expected.  Verify that the new HTTP API renders only the selection or layers, or both depending on the behavior setting.  

== Funding/Resources ==

Autodesk.  TBD: Selection improvements for the new "Fusion" based viewer.