[Qgis-developer] API changes

[Marco Hugentobler]

Hi Brendan,

> It was an optimisation feature.  The reason why it's linked to
> mUpdateTreshold is that's most efficient to grab all the Postgres
> features for a screen refresh all at once.

Oh, I see.
mUpdateTreshold was just for making the background buffer visible after the 
specified number of features have been drawn in the background buffer. The 
buffer swapping is (or was since it does not work with qt4) a very fast 
action. So I'm not sure if the coupling with mUpdateTreshold enhanced 
performance.

But the idea to draw while feature fetching is in progress is quite good. 
Something similar is done in the GPX and WFS providers, where the expat 
parser already starts parsing the xml when the first data arrives.

Regards,
Marco