Placing labels for points outside of separate polygon layer's boundary

Question

Is there a way to place all labels from three different point based vector layers outside of a boundaries of a separate polygon?

I have three layers of projects sites and want to have them all display outside of the island polygon. I have manually moved a few in the screenshot attached but would like to automate it as there are many project sites across the island.

Answer 1

As a possible starting point, you could use Geometry Generator (under the Placement tab for Labels) to move the labels outside the polygon. The following expression will generate a point on the boundary of your polygon (in my case, 'Country'), buffered by a certain amount (in my case, 0.2 degrees) to force it outside. The aggregate and convex hull are to cater for issues with multi-polygons - may not be required in all cases:

Code:

closest_point(
        aggregate(layer:='Country', 
            aggregate:='collect', 
            expression:=exterior_ring(convex_hull(buffer($geometry,0.2)))
    ),$geometry
)

You can then use a very similar expression in the Symbology, by adding a Geometry Generator to the original marker:

Code:

make_line(
    closest_point(
            aggregate(layer:='Country', 
                aggregate:='collect', 
                expression:=exterior_ring(convex_hull(buffer($geometry,0.2)))
        ),$geometry
    ),$geometry
)

This should be able to be extended to multiple point layers, per the original question.

Output on my single point layer looks like the following. Not a perfect solution, but might be a building block: