[Qgis-user] Variables in print composer

[Nyall Dawson]

On 23 Jun 2016 21:57, "Neumann, Andreas" <a.neumann at carto.net> wrote:
>
> Hi Uwe,
>
> All "map_xx" variables are only available on the map frame item itself
(when it is selected) - nowhere else. Items in print composer are on the
same hierarchy - so can't see each other's scope or variables in each
scope. But all items in a composition can see the "composition" variables
because they are one hierarchy above in the scope.
>
> That's a limitation you can't currently overcome. It would be nice to
cross-reference variables from other elements in the same hierarchy - but
it is not possible currently - at least I don't know how.

Andreas has summed it up perfectly. I originally had a function which
allowed items to access variables from another composer item, but had to
pull it out as it opened the risk of circular references (ie data defined
position for an item which uses item position variable from another item,
which in turn uses a variable from the first item). It's not trivial (or
fun) to solve, but if sponsorship is available I could fix this.

Nyall

>
> Andreas
>
> On 2016-06-23 13:36, Uwe Fischer wrote:
>>
>> Martin,
>>
>>
>>
>> thank you very much for your tip, but in the variables list no variables
of type „map" show up (please see attachment). But in print composter they
are present and visible.
>>
>>
>>
>> Mit freundlichen Grüßen,
>>
>>
>>
>> Uwe Fischer
>>
>>
>>
>> Von: Qgis-user [mailto:qgis-user-bounces at lists.osgeo.org] Im Auftrag von
Martin Stubbs
>> Gesendet: Donnerstag, 23. Juni 2016 12:46
>> An: qgis-user at lists.osgeo.org
>> Betreff: Re: [Qgis-user] Variables in print composer
>>
>>
>>
>> On 23/06/16 08:30, Uwe Fischer wrote:
>>>
>>> Hello List,
>>>
>>>
>>>
>>> what is the use of variables in print composer? A map frame has
variables assigned like map_extent_height and _width. But how to make use
of those variables? If I try to place a rectangle around the map frame
using the determined extent variables (plus something), I cannot use the
variables. There is a ‚data defined override' section in the Position and
size dialog for rectangles, but when I select ‚variable' it tells me that
there are no variables, which seems to be nonsense.
>>>
>>>
>>>
>>>
>>>
>>> Best regards, Uwe
>>>
>>>
>>
>> Uwe,
>>
>> When you select a Data_defined_override in Position and size, pick edit
from the list instead of variable. In the Expression string builder you
will find map_extent_height in the Variables list.
>>
>> Regards
>> Martin
>>
>>
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>
>
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