Whether a block of text fits into an object in a plan, and where it goes: the rectangle rule when the object fills
its rectangle, the circle rule otherwise (Viewer3D/docs/plan-labels-design.md §6). k is pixels per millimetre along
the baseline (bx, by); out.lines is the number of lines shown, 0 when the label does not fit.
Whether a block of text fits into an object in a plan, and where it goes: the rectangle rule when the object fills its rectangle, the circle rule otherwise (Viewer3D/docs/plan-labels-design.md §6). k is pixels per millimetre along the baseline (bx, by); out.lines is the number of lines shown, 0 when the label does not fit.