fix: Path2D arc continuity, Rect geometry, loader asset hygiene (audit mediums)

[obiot]

Batch 2 of the bug-hunt fixes — the loader/geometry mediums, all test-first (8 of 11 new tests red on the old code, plus one updated existing test).

Path2D.arc()/arcTo()/ellipse() started a hole instead of connecting

Per the native Path2D spec, an arc appended to a non-empty path is connected to the current point with a straight line — arcTo's own JSDoc even promises it. All three methods instead called moveTo() unconditionally. Under this release's multi-sub-path fill semantics (#1253), that stray sub-path is a hole: an arc appended to a filled outline punched a hole in the shape. Worth landing before 19.9 ships. (The SVG A parser had been quietly working around this — its comment even said "not ellipse/arc which call moveTo and break path continuity".)

Fix: a connectTo helper — lineTo when the path has content or the pen was explicitly placed, moveTo only on a virgin path. A new penMoved flag (reset by beginPath) distinguishes "virgin path" from "pen parked at (0,0)", so moveTo(P); arc(...) keeps its native connecting line. Preserved behaviors, each with a test: virgin-path arc() starts cleanly (no spurious origin line), the canonical circle-hole idiom (moveTo before arc()) still registers a hole via lineTo's gap detection, roundRect() stays a single sub-path, explicit moveTo holes still register.

One existing #1253 adversarial test ("a far disjoint arc() mid-path records a pen-up boundary") codified the old auto-detach accident — updated to assert native connect semantics, with a new companion test for the moveTo hole idiom. (rect() mid-path correctly keeps its boundary — native rect() does open a sub-path.)

Rect geometry

• right/bottom: this.left + w || w — an edge sitting exactly at coordinate 0 is falsy, so the getter returned the width/height. Now plain arithmetic.
• toPolygon(): passed the rect's live Vector2d[] into the pooled polygon — Polygon.setVertices stores vector arrays by reference, so transforming the "new" polygon corrupted the rectangle. Vertices are now cloned.

Loader asset hygiene

• load() mutated the caller's asset descriptor: the resolved URL (fontface url() unwrap + baseURL prefix) was written back into asset.src, so loader.reload() — which re-loads the same stored object — or simply load()ing the same manifest entry twice fetched base + base + src. The URL is now resolved into a shallow copy handed to the parser; caches, LOADER_ERROR payloads and failure tracking all keep the caller's original src (which also makes reload(src) keys consistent).
• unload() of a never-loaded fontface threw: FontFaceSet.delete(undefined) is a WebIDL TypeError, not a false return — the fontface case was the only one missing the membership guard every other type has.

Test plan

• 3 new spec files (11 tests) written failing-first: 8 red on old code, all green after
• 1 stale adversarial test updated to native semantics (+1 new hole-idiom companion)
• Full suite: 4609 passed / 0 failed / 15 skipped; eslint + biome + build clean

🤖 Generated with Claude Code

https://claude.ai/code/session_019t8kP8vp58ZrvaD2FqJU6A

[Copilot]

Pull request overview

This PR fixes several correctness issues uncovered during a “bug-hunt” audit across Path2D arc continuity, Rect geometry utilities, and loader asset lifecycle behavior, and adds/updates tests to lock in the corrected semantics (notably aligning Path2D arc/arcTo/ellipse behavior with native Path2D continuity rules).

Changes:

• Fix Path2D arc(), arcTo(), and ellipse() to connect to the current point (via a new connectTo helper + penMoved tracking) instead of incorrectly starting new sub-paths.
• Fix Rect.right/Rect.bottom origin-edge correctness and ensure Rect.toPolygon() returns an independent polygon (no shared live vertex array).
• Prevent loader.load() from mutating caller asset descriptors (avoids double-prepending baseURL on retries) and make loader.unload() for never-loaded fontface return false instead of throwing.

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated no comments.

Show a summary per file

File	Description
packages/melonjs/src/geometries/path2d.ts	Implements native-style arc/ellipse/arcTo continuity via connectTo + penMoved, preventing unintended hole sub-paths.
packages/melonjs/tests/path2d.spec.js	Updates an adversarial test to assert native arc connection semantics and adds a companion hole-idiom test.
packages/melonjs/tests/path2d-arc-connect.spec.ts	Adds focused spec coverage for arc/ellipse/arcTo continuity, virgin-path behavior, and hole/sub-path expectations.
packages/melonjs/src/geometries/rectangle.ts	Fixes right/bottom arithmetic and prevents toPolygon() from sharing rect vertices by reference.
packages/melonjs/tests/rect-geometry.spec.ts	Adds regression tests for right/bottom at coordinate 0 and toPolygon() vertex independence.
packages/melonjs/src/loader/loader.js	Resolves effective src without mutating the caller asset object; adds fontface unload membership guard.
packages/melonjs/tests/loader-asset-src.spec.js	Adds regression tests for load() not mutating asset.src and safe fontface unload behavior.
packages/melonjs/CHANGELOG.md	Documents the fixed behaviors for Path2D, Rect, and loader.

---

💡 Add Copilot custom instructions for smarter, more guided reviews. Learn how to get started.