Live preview of the real link while drawing + default link style = elbow arrow

[rustamgarifulin]

Why

While drawing/dragging a link, the overlay shows a straight dashed line (drawLinkPreview) instead of the link as it will actually render (routing, arrowheads, style). Also: default new link should be an elbow arrow instead of a straight line.

Proposed solution

Default style of a new link → elbow arrow:

• New links created with routing: "orthogonal" (Manhattan elbow) + end arrowhead (arrowheads.end = "arrow"/"triangle"). Was: default routing straight, no arrowheads (packages/scene/src/edge.ts:114-139).
• Decide WHERE default is set (computeCreateLink in scene vs state at creation) without breaking serialization of old links (fields optional — old links without routing stay straight, or migrate).
• Constants (arrowhead on/off, length, type) in constants.ts.

Live preview = the real rendered link:

• During draw-edge / endpoint-drag, show link with real rendering (routing + arrowhead + dash/color/lineKind) instead of straight drawLinkPreview.
• Source of truth = same path that draws committed link (renderLinks / edge-renderer in renderer-core). Build a ghost Link from preview endpoints through the same render path, or render a temporary link in the main layer.
• Handle preview endpoints not yet bound (point) or bound to anchor/outline — route correctly for all three.
• Both backends (Canvas2D + WebGL2); manual verification + snapshot if applicable.

Where in code: packages/scene/src/edge.ts / operations.ts (computeCreateLink) — default routing/arrowhead; packages/state/src/overlay.ts (drawLinkPreview, edgePreview) — replace line with real rendering; packages/state/src/editor.ts (applyLinkPreview, computeLinkPreviewEndpoints, applyCreateLink); packages/renderer-core edge-renderer — reuse for preview; constants.ts — arrowhead/elbow defaults.

Kind: feature

Alternatives / Notes

• UI/UX change → needs approval of details (arrowhead type, thickness, color, elbow behavior across relative positions) before implementing. Do AFTER anchor-overlay-ux bugs are closed.
• Status (2026-06-18): Section 1 (default = elbow) DONE (DEFAULT_LINK_ROUTING = "orthogonal" in buildLinkForCreate). Section 2 (applyLinkPreview / routeElbowPreview in editor.ts, render-orchestrator.ts) appears implemented; needs manual verification (both backends, all three endpoint types) before closing.