I'm printing QR-code that is generated on the fly in QGIS Print Composer. The URL to get the QR-code ist stored in a PostgreSQL database in the attribute-field "url".
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In Print Composer this works fine as long as the map, I use is part of an Atlas. When the map switches to another Atlas-feature, the generated QR-code is updated.
My problem is, that I want to use a map without the Atlas functionality. How can I get the URL only for the feature (supposing that only one feature is displayed) that is displayed on the map in Print Composer?
I was looking trough the expressions from QGIS, but did not find a suitable function to catch the data of a feature on a defined layer within the extent of a a map in Print Composer.