Preview Construction Lines

Overview

The Preview Construction Line feature allows operators to create temporary helper lines during a Preview session. These lines assist with geometry construction without becoming part of the committed drawing.

Visible on the canvas during the Preview session (amber, dashed)
Capable of supporting intersections, references, and geometric reasoning
Automatically removed when Preview is committed
Completely absent from DXF exports and toolpath output

Design philosophy: Minimal operator surface area — one toggle, one behaviour, zero management overhead. Construction lines assist geometry creation during Preview and are automatically discarded when the final geometry is committed.

The Construct Line Control

Item	Detail
Control name	Construct Line OFF / Construct Line ON
Location	Right flyout panel
Default state	Construct Line OFF (when Preview starts)
Availability	Enabled only when a Preview session is active
Scope	Affects new preview lines and broken preview lines only
Does NOT affect	Points, circles, arcs, imports, existing geometry, committed geometry

Construction Line Properties

Property	Construction Line (ON)	Normal Preview Line (OFF)
construction flag	true	false
transient flag	true	true
stable_id	None (not assigned)	None (until commit)
Colour	#ffcc00 (amber)	Standard preview colour
Dash pattern	[6, 3] — dashed	Solid
Supports intersections	Yes	Yes
Supports references	Yes	Yes
Committed on Commit Preview	No — discarded	Yes — becomes canonical
Appears in DXF	No	Yes
Appears in toolpath	No	Yes

Step-by-Step Workflow

Start Preview — the Construct Line control becomes available. Default state is OFF.
Enable Construct Line ON — subsequent new lines will be created as construction geometry (amber, dashed).
Draw helper lines — use any supported line operator. Lines appear amber and dashed on the canvas.
Use helper lines for references — construction lines support intersections, tangency, and all geometric reasoning operators.
Disable Construct Line OFF — subsequent new lines return to normal preview behaviour.
Create final geometry — use construction lines as references to place final geometry precisely.
Commit Preview — construction lines are filtered and discarded. Final geometry receives stable IDs and becomes canonical.

Commit Behaviour

Entity	construction	transient	stable_id
Construction line (before commit)	true	true	None
Construction line (after commit)	— removed —
Final geometry (before commit)	false	true	None
Final geometry (after commit)	false	false	Assigned

Example: A circle created using two construction lines as centre references: the circle has construction = false and is committed. The two construction lines have construction = true and are discarded. The circle remains; the helper lines disappear.

Dashed Circle

The Dashed/Circle operator creates the circle equivalent of a construction line — a reference circle displayed with dashed amber styling that is automatically removed on commit.

Dashed/Circle, Centre, R
Dashed/Circle, P1, R
Dashed/Circle, X, Y, R

Dashed circles support intersections and references during Preview. They are not included in DXF exports or toolpath output.

View Dashed/Circle Operator →

Examples

Example 1 — Locating a Circle Centre Using Construction Lines

Goal: Place a circle at the intersection of two reference lines
      without those lines appearing in the final drawing.

Step 1: Start Preview
Step 2: Enable Construct Line ON
Step 3: Line/Parlel, XAxis, D=50  → amber dashed line at Y=50
Step 4: Line/Parlel, YAxis, D=80  → amber dashed line at X=80
Step 5: Disable Construct Line OFF
Step 6: Point/Intof, L_const1, L_const2  → P0 = (80, 50)
Step 7: Circle/Centre, P0, R=25  → C0: committed circle
Step 8: Commit Preview
  → Construction lines removed
  → C0 remains at (80, 50), radius 25

Example 2 — Using a Dashed Circle as a Reference

Goal: Create a tangent line to a reference circle
      without the reference circle appearing in the final drawing.

Step 1: Start Preview
Step 2: Dashed/Circle, X=0, Y=0, R=40  → amber dashed reference circle
Step 3: Line/P0, YLarge, Tanto, C_dashed  → tangent line to dashed circle
Step 4: Commit Preview
  → Dashed circle removed
  → Tangent line remains as committed geometry

FAQ

Which line operators support construction mode?

All supported preview line-generation routes inherit construction intent automatically through the shared internal registration boundary. This includes: add_line, add_line_parallel_to_line, ui_line_perpendicular_to_line, ui_line_at_angle_from_point, ui_line_circles_tangent, ui_line_parallel_x_axis, ui_line_parallel_y_axis, ui_line_parallel_at_distance, ui_line_perpto_line_at_circle, ui_line_at_angle_from_circle, ui_line_px_xsmall_tanto_cx, ui_line_parlel_l1_tanto_cx, ui_line_tangent_to_arc, ui_create_broken_line_from_point_angle, and additionally trim, extend, offset, fillet, chamfer, and intersection-generated lines.

Does Construct Line affect circles, arcs, or points?

No. Construct Line affects only new preview lines and broken preview lines. It does not affect points, circles, arcs, imports, existing geometry, or committed geometry.

Can I use construction lines as inputs to intersection operators?

Yes. Construction lines support intersections, tangency, and all geometric reasoning operators during the Preview session.

What if I forget to turn Construct Line OFF before creating final geometry?

Any lines created while Construct Line is ON will be treated as construction geometry and discarded on commit. Turn Construct Line OFF before creating the final geometry you want to keep.

Are construction lines included in DXF exports?

No. Construction lines are completely absent from DXF exports and toolpath output. Only committed geometry appears in exports.

Dashed/Circle Operator → Full Documentation Download Manual v1.1