I have whipped up a demo where I am using OL to serve up a simple,
single-tile MapServer layer. My goal is to display a legend in an
adjacent div using a mode=legend call to MapServer. I almost have it
working, but the synchronization is a little off. My test is that I
have a scale-dependent layer in my map file and I am watching when the
this layer gets added to the legend. I am wondering if I am listening
for the wrong event.
I am listening for the 'moveend' event, grabbing the bounds and using
it to construct the legend call. Here is my (admitedly verbose) code.
map.events.register("moveend", map, function(e) {
var bounds = map.getExtent();
var boundsArr = bounds.toArray();
var currentExtent =
boundsArr[0]+'+'+boundsArr[1]+'+'+boundsArr[2]+'+'+boundsArr[3];
document.getElementById('legend_box').getElementsByTagName('img')[0].src="http://localhost/cgi-bin/mapserv?mode=legend&map=/Users/david/backendmaps/roads/roads_ol.map&mapext=";
+ currentExtent;
The legend is updating, but when the new layer appears on the map, it
doesn't often show up in the legend until the next zoom.
I see that the bbox value returned by getExtent is not the same as the
bbox values that OL plugs into the map request to MapServer. I assume
that this is because getExtent() is giving the value for the visible
map, not the whole image being requested.
This leads me to two questions:
1. If I am zooming in/out on a map is 'moveend' the correct event to
listen for if I want to grab the extent of the image being requested?
2. If so, is getExtent() the right call to get the extent of the new
image being requested?
Thanks,
David.
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