# Path editor

The project-authored path core accepts every SVG path command: `M/m`, `L/l`,
`H/h`, `V/v`, `C/c`, `S/s`, `Q/q`, `T/t`, `A/a` and `Z/z`, including repeated
parameter groups, implicit lines after move, packed arc flags, exponents,
relative forms and multiple subpaths. It rejects non-finite values, malformed
arity/flags and paths beyond the command limit.

Segments resolve to absolute geometry while retaining source command/form and
fragment offsets for the command table. Serialization intentionally normalizes
edited geometry; no editor metadata is emitted.

## Controls

- Every segment endpoint is an anchor.
- Cubics show both controls. `S` reflects the previous cubic control and marks
  the resulting handle as derived/dashed until edited.
- Quadratics show their one control. `T` reflects the previous quadratic
  control and marks it derived.
- Arcs expose endpoint, radii and derived center controls and show rotation,
  large-arc and sweep flags in the command panel.
- Handle radii and strokes use screen-oriented overlay styling so they remain
  usable across zoom levels.

The full selected-element/ancestor transform chain maps local path geometry into
root space. Pointer coordinates use its inverse, including an active preview
matrix; non-invertible chains disable handles. Dragging commits one transaction
on release; arrow keys use 1, Shift+10 or Alt+0.1 units and merge safely.

Segment splitting uses the mathematical midpoint: linear interpolation for
lines, de Casteljau for quadratic/cubic curves, and arc subdivision preserving
the ellipse. Path reversal reverses every supported segment/subpath and adjusts
controls/sweep where required.

## Current limits

The 0.1.0 UI supplies drag/nudge, split at 50%, reverse and a read-only numeric
command table. It does not yet supply node modes, multi-selection, deletion,
conversion, open/close, join/break/combine, subpath-start changes, arbitrary
split parameter, pen creation, snapping, simplification or boolean operations.
Visual editing expands shorthand/relative commands to normalized absolute data;
the dialog/help discloses that source-form change.