screen space offset or custom line anchor (for Projected3DLabel)

The position of a Projected3DLabel is given in 3D world space (using World unit) while the font size and direction are given in screen space (using Pixel unit).

A position offset (or a custom line anchor, that also allows x-offset) could help to position such a label more precisely in the screen space. Currently, an application would have to use a dynamic Position2DLabel and update its position manually (i.e., the application calculates position in world space to screen space) with every camera change.

Start by locating the Projected3DLabel and Position2DLabel entry points and reviewing how World and Pixel units are handled when the camera changes. Define whether the feature should use a screen-space position offset or a custom line anchor, then verify that labels can be positioned precisely without application-managed projection updates.

Written by the indexing model from the issue text.