[OpenLayers-Users] too much CPU used when zooming

[Christopher Schmidt]

On Thu, Nov 26, 2009 at 05:20:28PM +0100, Florent Coste wrote:
> Hello OpenLayer community
> 
> I'm a little surprised by the CPU used when zooming on any layer
> (WMS, TMS....)
> 
> It is like there is a spinning loop somewhere. For me this is like the tiles
> are displayed synchronously :
> It is looks like the map is not rendered until all tiles are retreived from
> the network.

This is definitely not true. Tiles are displayed asynchronously as they
are downloaded. 

> Inside FireBug, clear() method is eating time and CPU (i'm not used to
> firebug for profiling)

Note that Firebug is a poor tool for profiling DOM interactions, because
the 'last mile' of things like 'actually displaying the image' just gets
'lost'; there is no "DOM Rendering" method which the time gets attributed
to. Also, any useful profiling requires working against a non-singlefile
build, since it will just attribute time to whatever the first function is
on a line that's actually using the time, so you'll need to use a development
build to get any meaningful profiles.

> clear()7025.62%73.726ms*3316.139*ms47.373ms40.459ms97.064msOpenLayers.js
> (ligne 886)
> The CPU used during zoom is so high that the user experience is not good...
> 
> i'm available to test any patch to test/investigate the situation.

Good luck investigating the issue.

Best Regards,
-- 
Christopher Schmidt
MetaCarta