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 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
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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 the 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  // Renders the selected feature(s)
  RenderLayers = 2     // Renders the features on the map
  KeepSelection = 4    // Renders the selected feature(s) even if they are outside the current scale

Examples:

• RenderSelection | RenderLayers will render selection and layers within the current scale
• RenderSelection | KeepSelection will render only the selection regardless of scale

Add a SELECTIONCOLOR parameter to the existing GETDYNAMICMAPOVERLAYIMAGE. The color may be specified as an integer or hex string and the encoding is specified as 8 bit RGBA values.

Include support for "PNG8" in the FORMAT parameter of GETDYNAMICMAPOVERLAYIMAGE.

For the Web Extensions API add an additional signature for MgRenderingService.RenderDynamicMapOverlay that includes an MgRenderingOptions class:

  MgByteReader* RenderDynamicOverlay(MgMap* map, MgSelection* selection, MgRenderingOptions* options);

MgRenderingOptions will contain information on the image format, the behavior, and the selection color

class MgRenderingOptions
{
  MgRenderingOptions(CREFSTRING format, INT32 behavior, MgColor* selectionColor);
  STRING GetImageFormat();
  INT32 GetBehavior();
  MgColor* GetSelectionColor();
}

Update the existing WebLayout based ajax viewer to use the new API while maintaining the existing functionality. A new "selection" layer will not be added to the WebLayout based viewer.

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 will provide resources to implement the enhanced HTTP request.

Time permitting, DM Solutions will update the new "Fusion" based viewer to include a new "selection" layer.