[Qgis-developer] Data-defined symbol size is not backwards compatible to 2.8.2

[Andreas Neumann]

Hi,

Thanks for explaining. The assistant is very nice and a welcome 
improvement! Thanks for investing and working on it.

I had an issue that I had a size defined in 2.8.x with "scaling by area" 
which, when opened in QGIS master displayed much bigger. Once I changed 
that in 2.8x to "scale by diameter" the symbol sizes are identical in 
master.

So there seems to be an issue with converting "scale by area" symbol 
sizes from 2.8 over to QGIS master.

Should I open a bug report or is one open already?

Thanks,
Andreas

On 01.06.2015 20:05, Régis Haubourg wrote:
> Hi,
> here are the ideas behind this work, Nyall (code reviewer) and Vincent
> (author) could explain implentation choices more than me (funder):
>
> - get a more consistent UI with data defined widgets, and not "advanced
> fields". That way, size is in one place only.
> - offer an assistant on size varying common expression. You will find it at
> the bottom of the drop down widget. It computes max value from field or
> expression and allows normal user to do what other GIS do.
> - That assistant offer legend previsualisation, and generates a legend for
> map and composer. I wish we have a legend for any expression...
> - During implementation, we understood that symbol size was a multiplication
> factor of size varying factor. That implied that it was impossible to
> predict final screen size. The new implementation clears that up.
> - offer a size varying graduated renderer, allowing the use of
> classifications algorithms
> - offer a legend for diagrams (yes!)
>
> IMHO, we need to read previous versions correctly, but that sometimes need
> to read all features to retroengineer a size expression. Vincent have
> planned to polish that now that feature freeze is made.
>
> All that needs testing of course. I'm not totally satisfied with the
> assistant shortcut, hidden inside the size varying widget. If someone have a
> better UI idea..
>
> Hope that helps clarifying those changes.
> Cheers
> Régis
>
>
>
>
>
> --
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