Colliders take a frame's outline and tiles have their own surface (#193)

Issue #193 asked where friction, bounciness and density of a tile
live. Tiles had a fixed surface (friction 0.5, bounciness 0) and a
collider could not use the outline drawn on a texture frame (#141).
Both gaps are closed here.

- A collider has a fifth shape "Frame collision" with a Frame row.
  The frame is picked like a sprite's texture and stored as the
  value 'frame'.
- The shape is linked, not copied. Redrawing the outline in the
  texture tab changes every collider using that frame, in the editor
  and on the next play.
- The frame centre sits on the collider origin, one image pixel is
  one unit. The shape turns, scales and mirrors like any other.
- Every outline ring blocks. Each ring is split into convex parts the
  same way a polygon is.
- Without a frame, with a whole texture or with a frame that has no
  outline, the collider is drawn red as a box and blocks nothing.
- Move, Rapier, raycast, detection, hit test, drawing and footprint
  all resolve the frame. At runtime an entity looks the frame up
  live in the current project.
- A tile has Friction and Bounciness next to Solid and One-way. The
  rows only show when Solid is on. Defaults and mixing rules match
  the collider. Density is left out because a tilemap never moves.
- Tilemap cells are grouped by surface as well as by one-way angle.
  Ice and stone never merge into one rectangle, and every cell brings
  its surface to Move and Rapier.

Findings:

- A tile with a collision scale below 1 is no longer flush with a
  neighbour of another surface. It is inset there like at an open
  side, the same as next to one-way tiles today.
- A bounce test first measured 0.84. The ball had landed on the hero
  at the origin, not on the tile. On the tile it measures 0.993.

Tests:

- ./check.sh: 130 files, 1931 tests, exit 0 (was 129 / 1917).
- 14 new unit tests in tests/core/surface.test.ts. The Move tests run
  against the editor run and the physics system.
- 3 new e2e checks: 40l (surface rows follow Solid), 42e (collider
  has frame size, a walker climbs the slope in the frame).
- GM_STEPS=1-8,39-43 freshly seeded: ALL PASSED, 376 checks.
- Three counter-probes bite: Move ignores the tile surface (2 fail),
  Rapier ignores it (1 fails), frame shape falls back to a box
  (5 fail).
- Check sum 1198 is computed (1195 + 3), the full run belongs to CI.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

src/viewport/items.ts

@@ -17,6 +17,8 @@ import {
 import { findAsset, findAssetOf, type ObjectHolder, type Project } from '../core/model/Project';
 import { fontFileOf } from '../core/model/font';
 import { resolveTexture, type TextureRef } from '../core/model/texture';
+import type { FrameOutline } from '../core/model/frameOutline';
+import { colliderFrame } from '../core/properties/collider';
 import { enabledAlongChain } from '../core/properties/enabled';
 import { fontOf } from '../core/properties/fonts';
 import { resolveSceneObjectProps } from '../core/properties/resolve';
@@ -49,6 +51,8 @@ export interface DrawItem {
   tilemap: TilemapDraw | null;
   /** How often an `Emit` node has restarted this source; a change is what makes it start over. */
   emits: number;
+  /** The frame a collider of the shape "Frame collision" wears (#193), resolved here like a sprite's picture. */
+  frame: FrameOutline | null;
 }
 
 interface DrawList {
@@ -167,6 +171,7 @@ export function collectHolderItems(
       particles: asset.type === 'particles' ? asset : null,
       tilemap: asset.type === 'tilemap' ? resolveTilemap(project, asset.id, props) : null,
       emits: 0,
+      frame: asset.type === 'collider' ? colliderFrame(project, props) : null,
     });
   }
   const byId = new Map(items.map((i) => [i.id, i]));
@@ -204,6 +209,7 @@ export function collectWorldItems(world: World): DrawList {
       particles: e.type === 'particles' ? (findAssetOf(world.project, e.assetId, 'particles') ?? null) : null,
       tilemap: e.type === 'tilemap' ? resolveTilemap(world.project, e.assetId, e.props) : null,
       emits: e.emits ?? 0,
+      frame: e.wornFrame?.() ?? null,
     }));
   return { items, background: world.backgroundColor };
 }

src/viewport/symbols.ts

@@ -8,6 +8,7 @@ import {
   isTrigger,
   oneWayAngle,
   oneWayFacing,
+  outlinesOf,
 } from '../core/properties/collider';
 import { SHEET_EDGE } from '../core/shader/nodes';
 import type { NineSlice } from '../core/model/texture';
@@ -150,9 +151,10 @@ export function drawItem(
     case 'collider': {
       // Only the outline band is hit-testable, so clicks inside still reach the sprite that the
       // collider sits on.
-      const shape = colliderShape(item.props, IDENTITY);
+      const shape = colliderShape(item.props, IDENTITY, item.frame);
       traceShape(node, shape);
-      // A polygon that crosses itself collides with nothing, and says so in red.
+      // A polygon that crosses itself collides with nothing, and says so in red – as does a frame
+      // outline without a frame or without a drawn outline (#193).
       const color =
         shape.kind === 'polygon' && shape.pieces.length === 0
           ? Theme.colors.danger
@@ -201,7 +203,7 @@ function shapeBounds(shape: ColliderShape): Bounds {
               { x: p.x - shape.r, y: p.y - shape.r },
               { x: p.x + shape.r, y: p.y + shape.r },
             ])
-          : shape.outline;
+          : outlinesOf(shape).flat();
   return {
     left: Math.min(...points.map((p) => p.x)),
     top: Math.min(...points.map((p) => p.y)),
@@ -280,7 +282,7 @@ function traceShape(node: Graphics, shape: ColliderShape): void {
       return;
     }
     case 'polygon':
-      if (shape.outline.length >= 2) node.poly(shape.outline, true);
+      for (const ring of outlinesOf(shape)) if (ring.length >= 2) node.poly(ring, true);
       return;
   }
 }
@@ -299,10 +301,12 @@ function colliderOutlineHitArea(
   if (shape.kind === 'capsule')
     return { contains: (x, y) => Math.abs(distanceToSegment({ x, y }, shape.a, shape.b) - shape.r) <= band };
   if (shape.kind === 'polygon') {
-    const ring = shape.outline;
+    const rings = outlinesOf(shape);
     return {
       contains: (x, y) =>
-        ring.some((a, i) => distanceToSegment({ x, y }, a, ring[(i + 1) % ring.length]!) <= band),
+        rings.some((ring) =>
+          ring.some((a, i) => distanceToSegment({ x, y }, a, ring[(i + 1) % ring.length]!) <= band),
+        ),
     };
   }
   const hw = shape.w / 2;