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>
- A dimension snaps to what it draws: the objects of its block (read from a
file), expanded like block references, or else the lines generated from it
(Endpoint on their ends, Midpoint, Intersection, Nearest); Node on its
definition points.
- TEXT justified other than left-baseline (as read from DXF, group 11)
snaps (Insertion) and grips at its alignment point; attributes too.
- The snap grid starts at SNAPBASE and turns by SNAPANG (drawing variables,
defaults 0,0 and 0 degrees). SETVAR takes `x,y` for point variables.
- Hatches are left out of object snaps unless OSNAPHATCH is 1 (new session
variable, default 0 as in AutoCAD).
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
A circle in the aperture replaced the best Nearest candidate without
comparing distances, so a closer line drawn earlier lost to it.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
Follow-up to #318: a huge array of an empty or tiny block could spin up to
1e8 cells in the snap path without touching the entity budget.
Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
Running snaps only saw a block reference's insertion point. Now the objects
inside it snap where they are drawn: nested references and MINSERT arrays are
expanded, placed exactly by the reference's transform (non-uniform scale
turns circles and arcs into ellipses), and hidden objects or objects on layers
that are off are left out. Insertion also snaps to visible attributes.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
TAN and PER snaps need the other end of the line, so the first point of a
LINE (no base point yet) could never snap tangent: a belt line tangent to
two circles was impossible to draw.
Now, as in AutoCAD, a point prompt can accept *deferred* snaps:
- snap: with no base and the new `deferred` flag, osnap offers "Deferred
Tangent" (circles, arcs) and "Deferred Perpendicular" (circles, arcs,
lines, xlines, rays) where no other snap wins. The hit carries the curve
(`SnapHit::deferred`, `Deferred`, `SnapCurve`).
- `resolve_deferred` solves the line once the other end is known: tangent
or perpendicular from a point, tangent-to-tangent (common tangents of two
circles, new `Circle::common_tangents` in geom) and the perpendicular
mixes. Among several solutions the one nearest the picks wins. No
solution (point inside the circle, concentric or nested circles,
non-finite input) is `None`, never a panic.
- prompt: `Prompt::deferred()` opts a prompt in; `Input::Deferred` reaches
only such prompts, everywhere else the session turns it into the point it
was picked at, so other commands snap as before.
- LINE opts in for its first point (and the next one while the first is
still deferred). No solution reports and re-prompts; Undo drops the
deferred point. The rubber band shows the resolved line, also the
tangent-to-tangent one while hovering the second curve
(`Session::cursor_deferred`, set by the canvas).
- canvas: passes the prompt's flag to osnap and sends a deferred pick as
`Input::Deferred`.
Co-authored-by: Claude Opus 5.5 <noreply@anthropic.com>
