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

[Rob Marjot]

2014-07-02 1:30 GMT+02:00 Phil Scadden <p.scadden at gns.cri.nz>:

> 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.


Yes; onZoom, onPan events would trigger a serverside call to fetch the
vectors for the given BBOX.

Very true that I should first take this approach based on worldly
coordinates and from there see whether exchange in canvas coordinates is
going to improve performance significantly. Thanks.


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