[Qgis-developer] Patch Proposal #1974 Render caching

[Marco Hugentobler]

Hi Tim

> I remember chatting to Martin about this at the last hackfest. His main
> concern was that providers are not thread safe so we could run into
> issues e.g. try to run two threads on the same ogr datasource.

I think this concern was as we discussed layer tyling and rendering each tile 
of a layer in a thread. 
If a whole layer renders in a thread, we shouldn't have this problem because 
each layer has its own datasource object instance.

Regards,
Marco

Am Samstag, 24. Oktober 2009 14.40:40 schrieb Tim Sutton:
> Hi
>
> Marco Hugentobler wrote:
> > Hi Tim
> >
> > Wow, this is really cool and speeds up rendering in many situations.
> >
> > Now that every layer has its QImage to paint on, it might be a
> > possibility to render each in its own thread and have great performance
> > on todays quad core machines.
>
> I remember chatting to Martin about this at the last hackfest. His main
> concern was that providers are not thread safe so we could run into
> issues e.g. try to run two threads on the same ogr datasource.
>
> I have further plans for the caching system to that can realise speed
> improvements when panning and zooming in.
>
> I guess from the feedback there are no objections to me committing this
> patch.
>
>
> Regards
>
> Tim
>
> > Regards,
> > Marco
> >
> > Am Samstag, 24. Oktober 2009 00.41:39 schrieb Tim Sutton:
> >> Hi Devs
> >>
> >> I've been working a little on implementing some render caching to make
> >> QGIS feel more responsive and avoid unnecessary re-rendering of layers
> >> when nothing has really changed.
> >>
> >> I've finished writing a simple caching mechanism and would like to ask
> >> you to a) test and b) indicate if you are happy for this to go into
> >> trunk.
> >>
> >> The patch is here
> >>
> >> https://trac.osgeo.org/qgis/attachment/ticket/1974/qgis_rendercachepatch
> >>_v7 _23Oct2009.diff
> >>
> >> Note that caching is disabled by default - you need to enable it in the
> >> Options dialog, rendering tab.
> >>
> >>
> >> Regards,

-- 
Dr. Marco Hugentobler
HUGIS - GIS programming and consulting
Honrainweg 5
CH-8038 Zürich
marco at hugis.net
http://homepage.hispeed.ch/hugis/