[Qgis-developer] Re: New Symbology : merge borders on nodes for lines

[Martin Dobias]

On Wed, Feb 23, 2011 at 1:33 PM, Robert Rehammar <robert at rehammar.se> wrote:
> No I mean the main dialogue, please see the screencapture I attached
> last time. In the list of symbols defined here, why not make the order
> of the symbols defining the rendering order. Then symbols placed higher
> up in the list are rendered later, this would obsolete the symbol levels
> dialogue.

It is more complicated than just ordering the symbols. When using
'symbol levels' you actually define order of individual symbol layers.
Having two symbols (a,b) with two symbol layers each (a1, a2, b1, b2)
you should be able to specify arbitrary order of drawing the symbol
layers.

Not all combinations of ordering really make sense. Typically you want
something like: a1,b1,a2,b2 - that is first draw bottom layer of both
symbols, then draw top layer of both symbols. This produces a
desirable effect if you are drawing roads with outlines as seen in
professional maps. When you start thinking about rendering road maps
with various types of crossings, the order becomes more complex.

Regards
Martin