Dear list members, A few tickets related to rule based rendering were closed recently, but one still needs some thinking: 'symbol levels ignored for rule based rendering' I opened it here 6 weeks ago: http://trac.osgeo.org/qgis/ticket/3039 mhugent said it was addressed in patch #2832 Patch #2832 was partially applied by wonder, see: http://trac.osgeo.org/qgis/ticket/2832
Wonder wrote rightfully: "I've kept back the part regarding the symbol levels. The renderer should be able to apply multiple symbols if there are more valid rules. We need to give it some more thoughts on how to deal with the symbol levels." I've posted the following as an answer to wonder's message, but maybe it's easier to discuss it here (or should I reopen ticket 3039?): "Thank you wonder for putting it in the trunk! Here are some thoughts about how to deal with the symbol levels. IMHO, here are many examples where symbol levels are needed (and with the only workaround of having tens of layers). I cannot think of many examples where using several symbols (hence many matched rules) is absolutely required; even less examples where multiple matched rules AND symbol levels together are required ; for those examples (for instance: rule A and B), if we use the full patch rule_based_renderer.diff, there is the easy workaround of creating one rule C with (C <=> (A and B)) and putting it before A and B. Anyway, thinking of how to deal with combining symbol levels and multiple-matched rules will be easier if we can test rule based rendering with symbol levels. I am precisely working on this. I have just made my own build (based on 14481) by completely the patch in r14404 (including symbol levels). The first obvious needed feature would be to reorder the rules (change the priority order). Then, next to the "use symbol levels" check box, a warning should say that if symbol levels are activated, only the first matched rule will be applied. Then qgsrulebasedrendererv2.cpp should be modified to return "mCurrentSymbol" if symbol levels are not activated, and only the first matching rule if they are. Finally, symbol levels are saved in memory when closing the dialog box, but they are not saved to the file yet and this would need to be fixed. I'm working on rendering openstreetmap data in a customized way with filters based directly on the full-length OSM tags (but I cannot save my changes because of the above). Should we have the changes suggested here, users will be able to choose between multiple matched rules and symbol levels. We will then have use cases to think about where to go next. What do you think?" Thanks for your thoughts! Best regards, Mayeul _______________________________________________ Qgis-developer mailing list Qgis-developer@lists.osgeo.org http://lists.osgeo.org/mailman/listinfo/qgis-developer
