[symbology] respect mixed unit when applying symbol from list widget

[nirvn]

@nyalldawson , while improving the style manager, I stumbled on this irritating bug whereas a saved symbol containing mixed unit types (say a market with a map unit size and a millimeter outline) would fail to apply properly when selecting the saved symbol using the symbols list widget (i.e. our main way of serving symbols).

This PR fixes the situation by not calling setOutputUnit() when the unit type identifies a mixed-unit scenario.

[nyalldawson]

What's the even there for? Is it trying to respect the current size unit setting?

[nirvn]

@nyalldawson , funny you'd ask, I was wondering the same :) I didn't feel confident enough to simply assume we can get rid of it. That said, if you think it should go altogether, we can go down that road.

[nyalldawson]

Well.. it seems dangerous to me. A symbol designed with sizes in mm and then suddenly set to map units will almost always result in sizes too big or too little.

[nirvn]

@nyalldawson , that's indeed what was happening here (the other way around, a 500 map unit (meter) transformed into a 500mm).

Basically, as far as I understand, the units are already set up when layers are created and appended to the main symbol. The setOutputType() seems redundant.

[nirvn]

Actually, the call was added by @wonder-sk in this commit: 8b1f537

edit: fixing a bug you reported: http://hub.qgis.org/issues/10595 😄 --

[nirvn]

@nyalldawson , I'm wondering whether other underlying changes has made setOutputType() irrelevant. I've tried to remove the call altogether, and it very much looks like symbol loading is fine. Switching from mix units to mm-only to map unit-only works flawlessly.

[wonder-sk]

If the original bug is cannot be reproduced without setting unit type, let's remove it. Looking at the code again, I can't see a reason why the unit type should be explicitly set...

[nirvn]

@wonder-sk , commit updated to get rid of the setOutputUnit() call. Cheers.