[Qgis-developer] Symbol levels

[Hugo Mercier]

Hi Martin,

Le 16/04/2014 11:34, Martin Dobias a écrit :
> Hi Hugo
> 
> On Tue, Apr 15, 2014 at 3:07 PM, Hugo Mercier <hugo.mercier at oslandia.com> wrote:
>>
>> The UI asks for numeric levels, but, if I am correct, only relative
>> orders between two symbol layers are important.
>> Was there something else originally planned ? Something like a global
>> level to be able to order symbol layers of different vector layers ?
> 
> No, it was meant just for levels within one layer.

Ok, so ... why the UI asks the user for integers ? And what is the
meaning of two layers with the same number ?
What about a UI with the list of symbol layers and some up/down buttons ?

> 
> 
>> Another point : apart from performance issue, I cannot see any reason
>> why *not* to enable symbol levels. Are there situations were users do
>> want different symbol layers to overlap ?
> 
> I think there are such situations, from the top of my head:
> - with symbol levels you cannot see the rendering progress (everything
> is rendered at the end) - this makes quite a difference with big
> layers

If I am correct, you can still see the progress. You will see the first
symbol layer, then the second one, etc.

> - you don't always want the symbol layers to be blended (different appearance)

Now that Nyall gives an example of such rendering, that is clear.

> - not all renderers need to support symbol levels
> 
> I don't think we should go with symbol levels always on.
> 
> Regards
> Martin
> 
> 


-- 
Hugo Mercier
Oslandia