[OpenLayers-Users] Interactive hot spots on a map for large, complex vector geometries

[Phil Scadden]

On 2/07/2014 10:51 a.m., Rob Marjot wrote:
>
>
> One approach could be to start the download of vector geometries only 
> after finish rendering the WMS map. So, the user can already start 
> reading the map, deciding what to hover over. By that time, 
> ((over)simplified) vectors will nicely have been received and 
> rendered, so the actual highlighting will work. Thus implemented, I'm 
> expecting a better user experience that requiring the user to wait for 
> 1 second again-and-again for each hovered pixel / location.
So logic then would be for an onmove event to make a serverside call 
with BBOX which does WFS to fetch the vectors, and then then simplify 
(generalise) the geometry before passing them to the application. I 
remain uncertain as to whether putting them into canvas coordinates 
would give you the required time-boost. I would try NOT converting to 
canvas and seeing how you go but use the NET tab of debugger to time the 
download. If you convert to canvas, then you are going to have move 
outside OL for the drawing and mouse handling. It still wouldnt work in 
my application as even simplified to extreme (start and end point), I 
would have more than a 5000 objects to send down the web and render with 
only moderate zoom out. The web still imposes limitations on what can be 
done.

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