[Qgis-developer] Buffering/caching/auto-saving vector styles

Zoltan Szecsei zoltans at geograph.co.za
Sun Mar 2 02:10:49 PST 2014

On 2014/03/02 00:32, Ramon Andiñach wrote:
> On 01/03/2014, at 20:33 , Zoltan Szecsei wrote:
>> Hi All,
>> Sorry about the repeat, but Nathan felt I was hijacking his thread. Apologies.
>> If there are going to be modifications done to styling, please consider adding a feature whereby the various styles chosen or experimented with, are auto-saved for that mapsheet (perhaps in your project files).
>> I find when editing, edge-matching or QAing various mapsheets, I want to easily switch between styles - I might choose "single symbol" for the map I am editing, but "rule-based" for the adjoining maps. Rule based choices would change depending on scenarios, so it does not make sense to save a rule-based set (I could end up with too many).
>> So, what I am seeking is the ability to switch between the 5 style categories, and not lose the ones I may have set up a few minutes ago. If I close QGIS, and come back to the project later, I would like to see the last styles I had set up for a mapsheet, still be available when I click through the style options.
>> Hope I'm making myself clear.
>> Thanks & regards,
>> Zoltan
> Hi Zoltan,
> This is what I'm currently doing to sort of get this effect. This isn't as complex as yours, but it might help.
> For some of the geology maps (say geology.shp) that I work with I normally look at them coloured by rock type. So my styling for maps becomes (geology.qml). Sometimes it's also useful to look at them by other features, say age or formation name, so I'll make some other styles for those (geology_age.qml) and geology_name.qml). The the layer opens up they way I expect, but I can also switch betweeen styles reasonably quickly.
> Do the rule change completely? or are they variations? If they're variations then saving still be useful. You might end up with a style files that you used as a road rulesets template and vegetation ruleset template, and then modified these for the job at hand.
> -ramon.
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Thanks for the thoughts, Ramon.
The rules do change because I create the spontaneously. When I am QAing 
map compilations using various orthos, satellite imagery and whatever I 
have, the tone/clarity/resolution/ground colour changes as I pan accross 
the area, so I am changing the styles to (for that moment) suit the 
quality of the backdrop.
So what happens is, is that I might set up a "currently useful" rules 
based style, I then pan across the AOI, and get to an area that is 
tonally very different so I might switch single-symbol, and then a few 
minutes later go back to my rule-based - but then I have to set it up 
again (because I didn't manually save it).

The bigger picture:
What if the QGIS Dev Team considered creating a mapname.qgis file in the 
directory where the map is stored. When a map layer is deleted 
(removed), one could get a pop-up asking if the .qgis file should be 
deleted or not (or just leave it, so as not to be irritated by pop-ups 
each time you remove a layer)

The availability of this .qgis file is likely to then then inspire a 
host of other map-layer related uses (like the .prj file is for your 
project), but for me the currently useful one would be to stare the 
style-related states of the layer - ie: as you flip through the 5 style 
possibilities, you would not lose the most recent parameters you had set 
for any of the style options.

My 2c.



Zoltan Szecsei PrGISc [PGP0031]
Geograph (Pty) Ltd.
GIS and Photogrammetric Service

P.O. Box 7, Muizenberg 7950, South Africa.

Mobile: +27-83-6004028
Fax:    +27-86-6115323     www.geograph.co.za

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