MS RFC 63: Built-in OpenLayers map viewer¶

Date:	2010-09-25
Author:	Daniel Morissette (dmorissette at mapgears.com)
Author:	Alan Boudreault (aboudreault at mapgears.com)
Last Edited:	2010-10-26
Status:	Adopted on 2010-10-29. Implementation complete.
Version:	MapServer 6.0
Id:	$Id$

Overview¶

Users often request for a simple way to test mapfiles. This RFC proposes a simple way to preview, test and navigate a mapfile with MapServer using a built-in OpenLayers based map viewer that will be triggered via the cgi. This is for testing/development purposes only and not for production or deploying full-featured sites. This will use the a built-in openlayers template. It will return a simple html viewer based on OpenLayers.

Note that GeoServer already provides a similar functionnality and this is what this RFC was inspired from.

Implementation Details¶

In order to implement this enhancement, the following changes should be made in the MapServer codebase:

Add a built-in openlayers template.
Some new template tags will be needed. These tags will be used to construct the mapserver cgi url.
- [mapserv_onlineresource]
  
  or
- [protocol]
- [host]
- [program]
See ticket 3552 for more detail.

The template will be triggered using one of the following ways:

Using mode=browse&template=openlayers: The viewer will be initialized based on the mapfile defaults, and some of the traditional mapserv CGI params may also work (such as map size, layer selection, etc.)
Using FORMAT=application/openlayers in a WMS GetMap request: The rest of the GetMap parameters would be used to configure the map to view (BBOX, WIDTH, HEIGHT, LAYERS, etc.)

Both cases would call the same functions internally to produce a simple OpenLayers viewer with one singletile layer for the whole map with the selected layers.

Here’s the simple viewer html code that could be used:

<html>
<head>
  <title>MapServer Simple Viewer</title>
    <script src="http://www.mapserver.org/lib/OpenLayers-ms60.js"></script>
    </head>
    <body>
      <div style="width:[mapwidth]; height:[mapheight]" id="map"></div>
      <script defer="defer" type="text/javascript">
        var map = new OpenLayers.Map('map',
                                     {maxExtent: new OpenLayers.Bounds([minx],[miny],[maxx],[maxy]),
                                      maxResolution: [cellsize]} );

        var mslayer = new OpenLayers.Layer.MapServer( "MapServer Layer",
            "[mapserv_onlineresource]",
             {layers: '[layers]'},
             {singleTile: "true", ratio:1} );
        map.addLayer(mslayer);
        map.zoomToMaxExtent();
      </script>
</body>
</html>

OpenLayers Dependency¶

Obviously, this functionnality needs the OpenLayers javascript library. A minimal build will be used and hosted on the MapServer website at http://www.mapserver.org/lib/OpenLayers-ms60.js. The “ms60” suffix in the OpenLayers-ms60.js filename is so that we can increase the version number in the future if/when needed to match the requirements of future releases of MapServer.

Users will also be able to use their own OpenLayers library in one of two ways:

Using a environment variable: by setting the environment variable MS_OPENLAYERS_JS_URL, MapServer will use that url rather than the default one.
Using a CONFIG setting in the mapfile: by adding the config variable MS_OPENLAYERS_JS_URL in a mapfile, MapServer will use that url rather than the default one.

Files affected¶

To determine...

Further Considerations¶

In the future, we may provide a mechanism to support multiple frameworks and ship generic templates with MapServer.

Bug ID¶

The ticket for RFC-63 (containing the implementation) can be found here.

Ticket 3549

Ticket 3552

Voting history¶

Adopted on 2010-10-29 with +1 from SteveL, DanielM, JeffK, AssefaY, TomK, TamasS, SteveW and PerryN.

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