[Qgis-user] Variables for colour values

[Matthias Kuhn]

Hi,

Instead of adding a new "hard" field to the data you may also add a
"virtual field" that you can then use for several data-defined
properties. That will also reflect the changes if the data below
changes. I think this should be pretty much what you want?

Regards,
Matthias


On 02/24/2015 03:17 PM, Mofo Yoda wrote:
> Hi,
> When I use data defined properties, I can set the expression for colour and width etc.
> But what I really want to do is to set the variable once and use the same variable inside multiple expressions for many symbols in my project.
> So I can change the value of that variable in one place, and automatically change all symbols, that use this variable in their expressions. 
> It should be a kind of global variable for all symbols.
>
> The only workaround I can think of is to store variable values as fields of data itself (I use postgis db, so this is potentially possible) and use a fields value in the expression, 
> like “fill_color_field” for color, but that’s very inconvenient, and I guess there should be a better way. 
> Is it possible using ‘function editor’ in expression maybe?
>  
>
>> On 24 Feb 2015, at 16:07, Jonathan Moules <J.Moules at hrwallingford.com> wrote:
>>
>> Hi,
>> Yes, it is.
>> You want the "Data defined properties" button, which you'll see when you click on a style (in 2.6.1, it's at the bottom of the list of style options.
>>
>> The variables need to be of a specific datatype/structure for each item you want to style. So Pen Width requires a double. Colour is more complex, requiring a RGBA string. The dialog shows what's necessary.
>>
>> Cheers,
>> Jonathan
>>
>> -----Original Message-----
>> From: qgis-user-bounces at lists.osgeo.org [mailto:qgis-user-bounces at lists.osgeo.org] On Behalf Of Mofo Yoda
>> Sent: Tuesday, February 24, 2015 11:19 AM
>> To: qgis-user at lists.osgeo.org
>> Subject: [Qgis-user] Variables for colour values
>>
>> I wonder if it’s possible to use variables for colour values, line widths etc? I have rule-based styling with lots of rules, and I want to change the colour value in one place and not in every rule that uses the same symbol. I’ve been using variables a lot in CartoCSS styling, but I really miss them in QGIS. Since I can define project colours with names in QGIS, i thought it may be possible somehow.
>> I’m on QGIS 2.8 for OS X.
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