Expected output for Geometry Generator of Polygon

Question

I have a number of point features and created various font and simple markers for each point.

I now want to add background for the Font marker, so that it would be readable against the basemap background. I assume a way to do this would be to add a geometry generator (polygon) for the layer. Now, I have a trouble creating the output desired to produce the polygon.

I have tried using make_polygon, but I can't understand what arguments need to be to produce a polygon. Ideally I want to specify origin point ($geometry=original point layer location) and -x, x, -y, y extents. Maybe there is another way to accomplish this?

TL;DR: Need to create a polygon with defined size using geometry generator based on point layer.

Answer 1

The make_polygon() function expects a line as input. Use the make_line() function to create a line.

The make_line() function expects a series of points as input. Use the make_point() function to create points.

The make_point() function expects input in the format of x,y. Use the variables $x and $y to get the x and y coordinates of the current point feature.

To make a rectangular polygon

make_polygon( make_line( make_point($x+dx, $y+dy), make_point($x+dx, $y-dy), make_point($x-dx, $y-dy), make_point($x-dx, $y+dy) ) )

Substitute appropriate values for dx and dy. They represent the amount to change the x and y coordinates of the current point, respectively.

• Use a fixed amount if you want the same size rectangle for each feature.
• If you want a different size rectangle for each feature, add a field called dx and a field called dy. Put the field names into the expression as "dx" and "dy".

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