[Qgis-developer] Bringing diagrams into labeling-ng

[Martin Dobias]

Hi Paolo

On Wed, Feb 16, 2011 at 7:57 AM, Paolo Cavallini <cavallini at faunalia.it> wrote:
> Il giorno mer, 16/02/2011 alle 00.50 +0100, Martin Dobias ha scritto:
>
>> - what would be the impact on the labeling itself?
>
> Beware however: in ordinary machines, hundreds of labels are enough to
> keep QGIS busy for a long time. I think this should be solved, as adding
> diagrams can only add to the problem.

PAL has several stages: 1. extraction of label candidates of features
2. evaluation of cost of each candidate 3. solution of the conflicts.
IIRC the slowness is caused by evaluations of cost, especially
polygons need quite complex computation. This could be approached with
a smarter evaluation that does not do so many operations. What I mean
here is that the library itself is quite fast, just one piece causes
the slowness.

Martin