[Qgis-developer] Data-defined buttons for "en masse" size and rotation

[Régis Haubourg]

Hi Anita, 
I was not sure on first message of Vincent, but now I'm sure, I'm the funder
of such features ;-). I did not spoil that work before, because that took us
a loooong time to validate the contract. We should have make it for 2.8 at
start.. 2.10 will be the goal. 
Discussion with community is more than welcome of course!

What we need is :
- use data defined widget used in labeling windows in symbology screens.
This will be more consistent and was discussed previously on the list. I
found some money for that, hope community still agrees

- add graduated classification for size, with same classification options as
for current renderer. This will be possible to set both color graduated
legend and size varying legend that way, with legend enabled. 

- add a GUI assistant to help users define expressions for continuous size
varying expressions. We currently have that in "advanced fields", which
appears to be confusing to users here. We would like to plug that assistant
with "label" expressions widgets.  We only propose squaretail (= circle
surface or exp 0.5), linear and flannery  (exp 0.57) at start. If you know
other interesting functions, feel free to submit.
Flannery gives good results and is considered as better classification
method by some cartographers. No objection to keep circle surface as default
instead if you have other references. This topic needs precise mockups
because it's not easy to understand interactions of datadefined tools on
symbol / marker level from a UX point of view. 

- when using the GUI assistant or the graduated classification, we will
enable a legend for mapcanvas and composer 's legend. That legend will be of
this type  [0]

- we will also add test and documentation in english and french in qgis
documentation. 

Please tell us how that sounds to you. 

Cheers, 
Régis

[0] http://s14.postimage.org/3jr9kcmgh/muesure.png




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