[Qgis-developer] Ellipse renderer

[Martin Dobias]

Hi Marco

finally I'm back :-)

On Tue, Jun 14, 2011 at 3:48 PM, Marco Hugentobler
<marco.hugentobler at sourcepole.ch> wrote:
> - A pointer to the rendered QgsFeature* has been added to
> QgsSymbolV2RenderContext (such that the symbollayer has the possibility to
> check the data defined attribute values)
>
> - A symbollayer has the possibility to specify which attribute fields it needs
> for rendering (by default, QgsSymbolLayerV2::usedAttributes returns an empty
> set).
>
> - The symbollayer widgets receive a pointer to their vector layer. Normal
> symbol layer widgets don't use it, the widgets of  data defined symbol layers
> get the available fields through that pointer.

I have looked at the code and these changes look OK to me.

However would not it be better to add data defined fields to the
simple marker symbol layer instead of creating a new one? The ellipse
symbol layer seem to duplicate a lot of code, the only difference I
see is that ellipse marker supports unequal width and height).
Additionally it will probably make sense to add such data defined
rendering also e.g. for simple line and simple fill.

Regarding the widget for symbol layer properties - I do not really
like the tabbed approach (the second tab with lots of combo boxes
looks scary :-), though I am not sure what would be the most user
friendly approach. I am merely a fan of "Advanced" buttons that show
this functionality (maybe in a separate dialog or by adding further
widgets). I guess this way the regular users do not get overwhelmed
with complexity and power users are happy.

One more technical issue: in the ellipse symbol layer you store
indexes together with the field names. This is suboptimal and the
field indexes should be resolved in startRender() method.

This is going to be another nice addition to the new symbology!

Regards
Martin