MapGuide RFC 56 - Add additional map commands to GETDYNAMICMAPOVERLAYIMAGE

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	October 6, 2008
Last Modified	Chris Claydon Timestamp
Author	Chris Claydon
RFC Status	(draft, proposed, frozen for vote, adopted, retracted, or rejected)
Implementation Status	(pending, under development, completed)
Proposed Milestone	2.1
Assigned PSC guide(s)	(when determined)
Voting History	(vote date)
no vote

Overview

The proposal is to add additional, optional parameters to the GETDYNAMICMAPOVERLAYIMAGE HTTP request format to allow setting the map view state. These parameters are already supported by the GETVISIBLEMAPEXTENT and GETMAPIMAGE HTTP request formats.

Motivation

The MGOS AJAX and Fusion viewers currently make (at least) two HTTP requests to render each new map image - one to GETVISIBLEMAPEXTENTS, which is used to set the current map view, and one to GETDYNAMICMAPOVERLAYIMAGE. The first request returns the extents of the map after the view state parameters have been applied. But in some cases this information is not required, and the two calls could easily be combined into one. This would provide increased efficiency and scalability.

Proposed Solution

The proposal is to add support for the following parameters to the GETDYNAMICMAPOVERLAYIMAGE HTTP request format:

SETDISPLAYDPI	Sets the display resolution in dots per inch
SETDISPLAYWIDTH	Sets the display width in pixels
SETDISPLAYHEIGHT	Sets the display height in pixels
SETVIEWSCALE	Sets the required view scale
SETVIEWCENTERX	Sets the view center point x coordinate in mapping coordinates
SETVIEWCENTERY	Sets the view center point y coordinate in mapping coordinates
SHOWGROUPS	Sets the list of groups to display
HIDEGROUPS	Sets the list of groups to hide
SHOWLAYERS	Sets the list of layers to display
HIDELAYERS	Sets the list of layers to hide

Implications

The code to parse and apply the view setting parameters already exists in the MG web tier. Implementing it for GETDYNAMICMAPOVERLAYIMAGE is therefore very straightforward. No changes are required in the MG server code to support the change.

Test Plan

Web tier unit tests should be added to test the new parameters.

Funding/Resources

Autodesk to provide resources to implement web tier changes. Updates to AJAX and/or Fusion viewers can be made by the appropriate parties following the web tier updates.