Fine-tuning curved text positioning

Question

I'm trying to label features using the geometry generator (QGIS 3.8). I used the following expression to build a simple circle :

buffer(centroid($geometry), 500)

In Placement i used Using Perimeter (curved)

The labeling is working pretty good except some of my features label are written clockwise and some counterclockwise. How could i control this rendering ?

Furthermore i would like the mid-point of my labeling string to be at the most northern point of the circle ...

How could i achieve that ?

Answer 1

For clockwise/counterclockwise fix, you can allow upside-down labels. In label rendering tab set Show upside-down labels to allways.

For centering the label to the north, I figure out a workaround based on Using QGIS Geometry Generator to get rectangle from point?. Using geometry generator in label placement tab, you can create buffer of tiny polygon witch starts at such a place that the label is then rendered on top. Just adjust the buffer size to your needs.

buffer(geom_from_wkt( 
    'POLYGON(('|| 
        (x(centroid($geometry)))||' '||(y(centroid($geometry)) - 0.0001) ||','||
        (x(centroid($geometry)))||' '||(y(centroid($geometry)) + 0.0001) ||','||
        (x(centroid($geometry)) + 0.0001)||' '||(y(centroid($geometry)) - 0.0001) ||','||
    '))'
    ),
    0.3
)

Note that geometry generator for label placement is available from version QGIS 3.8