I would like to build a rectangle (shape or symbol) with a given size (height/length) from the attribute-table.
In detail: I build a Atlas of maps with alternating sizes, like 145x129 or 165x129. The size of every feature is written in the attribute table of the coverage-layer. So far so good: every map got his own defined size using data defined override for map length and height.
But now I would like the bounding boxes of the atlas-maps to be shown as overlays on the map in my canvas. (Like you can do with the overlay-function in the print composer)
The best approach seemed to be to use the geometry-generator and build a polygon around the centroid of the feature. I already started a post months ago: Using QGIS Geometry Generator to get rectangle from point? With the result, that it is not possible because the "Geometry generator does not support calculations inside WKT". I still have that problem to solve. Do anyone know a other approach?