Thanks. That's definitely a cleaner setup, but it didn't really solve the problem I was having. Before the box would look like it was being drawn properly, but then the persistent copy would be vertically offset. Now it's offset from the time I start drawing. Which is an improvement, because at least it will be easier for users to draw the box they want. Here's a screenshot to show what I mean:
http://imgur.com/5cJ4H The Box was drawn exactly from Cape Fear to Cape Hatteras, marked with little black dots on the screenshot. However, the box itself starts drawing a bit above the location of the cursor. It seems the further I get from the top of the display, the further displaced the box is. It is impossible to get closer than ~2cm from the bottom of the map. There also seems to be a very slight horizontal displacement. Any thoughts on what might cause this displacement? At this point, no transformation is being done--at least not in any of my code. Cheers, Cliff On Fri, 2009-11-13 at 09:58 -0700, Scott Lewis wrote: > I did something like this using one of the examples on the OpenLayers > site, modified slightly. Here's what I used: > > boxControl = new OpenLayers.Control(); > OpenLayers.Util.extend(boxControl, { > draw: function() { > this.box = new OpenLayers.Handler.RegularPolygon(boxControl, > {"done": this.notice}, {sides:4, irregular:true, persist:true}); > this.box.activate(); > }, > > notice: function(geom) { > // whatever you want it to do after the box has been drawn > } > }); > > // then add the boxControl to the map > > This works pretty nicely. Note that "geom" will be in the same > projection as the map, so if you want the output to be in another > projection (like a latitude/longitude display) you will have to go > through the geometry and transform the points. Also, you may have to go > through the geometry to determine which point is which (it doesn't > always start with the upper-left corner, and it's not always clockwise > or counter-clockwise). If interested, I can post some of the functions > I do for that. > > I hope this helps, > > Scott Lewis > NSIDC > > J. Cliff Dyer wrote: > > I'm trying to draw a box on a map, have it persist until another box > > gets drawn, and submit the coordinates of the box to a form. I'm doing > > this to allow the user to search for objects within a given area. > > > > I'm doing this by using an OpenLayers.Handler.Box tool in a custom > > OpenLayers.Control, which then uses to the "done" callback of the draw > > method to create (or recreate) an OpenLayers.Feature.Vector and populate > > (or repopulate) a search form. > > > > My immediate problem is that the persistent box is not in quite the same > > location as the box the user just drew. I suspect this has something to > > do with projections, but since I never explicitly set projections, I'm > > not sure where the error sneaked in. > > > > More generally, I'm not sure I'm taking the optimal route from the > > bounds passed to the callback to the Vector feature. Currently, I do > > the following: > > > > 1) Take the incoming OpenLayers.Bounds object, > > 2) Get an OpenLayers.Pixel from the the corners > > 3) Get the coordinates of each pixel using map.getLonLatFromPixel > > 4) Create a new OpenLayers.Bounds > > 5) Extend it to my new coordinates > > 6) Convert it to a geometry > > 7) Convert it to an OpenLayers.Feature.Vector > > > > Then I take the coordinates from step 3) and populate a form with them, > > which I then submit to my application server side. > > > > The code for this is pasted here: http://pastebin.com/m300c24a5 > > > > Any pointers on how to do this more cleanly would be much appreciated. > > > > Cheers, > > Cliff > > > > > > > > _______________________________________________ > > Users mailing list > > [email protected] > > http://openlayers.org/mailman/listinfo/users > _______________________________________________ Users mailing list [email protected] http://openlayers.org/mailman/listinfo/users
