[OpenLayers-Dev] preliminary UTFGrid support in OpenLayers

[Tom MacWright]

> In addition, I'd like to add support for highlighting regions in the
grid.  I've got a plan for doing this, and while I don't want to hold
up inclusion of the existing functionality, I do think the highlight
functionality might inform a bit more how things could be structured.

Highlighting is a bit of an unusual question with UTFGrid. It's a
tiles-only format - original geometries are never sent over in their full
form. I've written a quick proof of concept, glower:
http://mapbox.com/glower/# which does an overlay of canvas tiles over
normal tiles and implements some simple edge-squaring, anti-aliasing (by
hand :/ ), and such. The OpenLayers implementation - I'm not sure if I've
seen whether it loads all tiles by default or lazy-loads (as the other
implementations do), but basically you need to resolve tile boundaries and
do a bit of odd logic for figuring out which features are equal.

On Sat, Feb 25, 2012 at 6:35 PM, Tim Schaub <tschaub at opengeo.org> wrote:

> Hey Matt,
>
> Thanks for this great contribution.  It's been high on my list of
> desires to get UTFGrid support into OpenLayers, and it looks like you
> have done a nice job of it.
>
> After a quick preliminary review, I do have a few comments.  First,
> we'll need some tests to go along with this addition.  Beyond that,
> I've got some suggestions about the layer API that I hope you'll be
> amenable to.  I think it would make sense to provide a method on the
> layer to get attribute data for a map location.  This functionality is
> currently in the control, but can see situations where it would be
> useful to access this and awkward to have to add a control.  I'll
> provide a pull request for this and some additional tweaks.  Note that
> my pull request will look a lot smaller if you merge the latest master
> into your utfgrid branch.
>
> In addition, I'd like to add support for highlighting regions in the
> grid.  I've got a plan for doing this, and while I don't want to hold
> up inclusion of the existing functionality, I do think the highlight
> functionality might inform a bit more how things could be structured.
>
> I'll leave more comments on your pull request.
>
> Tim
>
> On Thu, Feb 16, 2012 at 12:08 PM, Matt Perry <perrygeo at gmail.com> wrote:
> > Hey all - I'm excited to share my implementation of OpenLayers support
> > for UTFGrids. I wanted to get some feedback before doing a pull
> > request.
> >
> > Just a little background: UTFGrids are json "hit grids" used to
> > provide a high degree of interactivity. For example, you can have
> > mouseover events that display the attributes of the features *without*
> > fetching additional data from the server. The best demo of the concept
> > is probably http://mapbox.com/demo/visiblemap/.
> >
> > This functionality exists in the wax library and is largely deployed
> > with ModestMaps. I've ported it to native OpenLayers code to better
> > integrate with OL event handlers and such. There are three additional
> > components: a UTFGrid Layer, Control and Tile. It has both ajax and
> > jsonp loading protocols, tries to keep a clear separation between the
> > grid layers, the grid controls and callbacks which allows things like
> > multiple handlers and multiple hit grids per map.
> >
> > Some example code:
> >        var world_utfgrid = new OpenLayers.Layer.UTFGrid(
> >            'UTFGrid Layer',
> >            "http://tiles.example.com/world_utfgrid/${z}/${x}/${y}.json"
> >        );
> >        map.addLayer(world_utfgrid);
> >
> >        var control = new OpenLayers.Control.UTFGrid({
> >            'div': 'attrsdiv',
> >            'layers': [world_utfgrid],
> >            'handlerMode': 'move'
> >        })
> >        map.addControl(control);
> >
> >
> > Some demos:
> > http://labs.ecotrust.org/utfgrid/events.html
> > http://labs.ecotrust.org/utfgrid/multi.html
> >
> > and source:
> > https://github.com/perrygeo/openlayers/tree/utfgrid
> >
> > Any thoughts on getting this into 2.12? This is my first substantial
> > effort in extending OpenLayers so if you have any critiques or
> > concerns that need to be addressed before a pull request would be
> > considered, let me know.
> > --
> > ·´¯`·.¸. , . .·´¯`·.. ><((((º>`·.¸¸.·´¯`·.¸.·´¯`·...¸><((((º>
> > "The best way to predict the future is to invent it."  -- Alan Kay
> > Matthew T. Perry
> > http://www.perrygeo.net
> > http://viedevelo.wordpress.com
> > _______________________________________________
> > Dev mailing list
> > Dev at lists.osgeo.org
> > http://lists.osgeo.org/mailman/listinfo/openlayers-dev
>
>
>
> --
> Tim Schaub
> OpenGeo http://opengeo.org/
> Expert service straight from the developers.
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