[Qgis-developer] comments on qgsvectorlayer.cpp

[Marco Hugentobler]

On Friday 31 August 2007 10:07:15 you wrote:

> I wanted to implement rendering in a background thread some time ago
> to allow some features we really miss, like:
> - interruption of rendering
> - GUI interaction during rendering
> - prerendering of areas near the border (as OpenLayers or GMaps do)
> This needs a deep analysis of how it would work, where to put
> synchronisation etc.

Yes, it would be much work and is quite difficult.

> and it will need also some architecture changes - 
> e.g. data providers do not provide thread-safe access, so concurrent
> reads from providers would end up with incorrect results.

Wouldn't it be possible to have only one rendering thread so that thread safe 
providers are not needed (at least as a first step)? 
But yes, on multiprocessor machines, it would be really cool to have different 
threads rendering different tiles. Do you have an idea how providers could be 
made thread safe? 

Marco



-- 
Dr. Marco Hugentobler
Institute of Cartography
ETH Zurich
Technical Advisor QGIS Project Steering Committee
marco.hugentobler at karto.baug.ethz.ch