Resting the cursor on a snap point acquires it for tracking (seven at
most; resting again releases it). Acquired points send horizontal and
vertical alignment paths, or every polar angle with POLARMODE 2; the
cursor snaps where two paths cross, where a path crosses an object, or
onto the nearest path. EXT runs a line or arc on from an acquired end,
PAR gives a path parallel to a rested-on line through the base point,
APP snaps where objects would meet if extended. Direct distance entry
follows the path the cursor is on. POLARMODE is now AutoCAD's bitcode;
POLARADDANG and AUTOSNAP are new.
The engine owns all of it (Session::snap_cursor, snap/tracking.rs); the
canvas draws the + markers, dotted paths and tooltip.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Midpoint snaps halfway along the length of an elliptical arc or open spline.
Perpendicular and Tangent from a base point find every foot point and
tangent point on ellipses, elliptical arcs and splines (the one nearest the
cursor wins, as for circles): tangents to an ellipse exactly through the unit
circle, the rest by sampling the parameter range and bisecting each sign
change, with fixed iteration bounds. Quadrant on an elliptical arc offers only
the quadrant points the arc passes through.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Marco Arnulfo