Blender already had the ability to sample the depth with an eyedropper
and fill the focus distance (see `"ui.eyedropper_depth"`). But this feature
was fairly hidden. You had to hover over the `focal_distance` property
in the camera data panel and then press `E` (then sample a distance
in the 3D viewport).
This patch adds a `prop_data_path` property to the `ui.eyedropper_depth`
operator to allow specifying the property that should be filled with the
depth value.
The idea for this is taken from `wm.radial_control`, which also uses this
approach to write to a property. This allows us to add the eyedropper
as a button.
Pull Request: https://projects.blender.org/blender/blender/pulls/121486
7f8d4df410