Read the pixel size of a texture in a graph (#262)

A graph had no way to know how big a picture is. An icon sprite with a
fixed size therefore stretched every icon of another size, an 8x8
pixel-art icon in a 16x16 slot was drawn twice as big.

- New data node Texture size. It takes a texture, a frame or a pixel
  art and hands out width and height in pixels, 0 x 0 for none.
  Wired into a sprite's width and height, the picture shows pixel for
  pixel.
- GraphLookup gets textureSize. The project answers it with the same
  pictureSize rule a sprite uses to size itself.

Tests:

- ./check.sh: 2749 tests, CHECK EXIT 0.
- 2 catalog cases (a picture, no picture) and one test against a real
  project: pixel-art sheet, single frame, missing texture.
- No e2e check and no counter-check for this node.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

src/core/graph/lookup.ts

@@ -46,6 +46,8 @@ export interface GraphLookup {
   curve(assetId: string): readonly VectorPoint[] | null;
   /** A Struct asset as a run knows it: a name and field names, nothing else travels (#254). */
   structType(assetId: string): StructShape | null;
+  /** A texture's, frame's or pixel-art frame's own size in pixels; null for no picture. */
+  textureSize(pictureId: string): { w: number; h: number } | null;
 }
 
 export interface StructShape {
@@ -58,4 +60,5 @@ export const NO_LOOKUP: GraphLookup = {
   machine: () => null,
   curve: () => null,
   structType: () => null,
+  textureSize: () => null,
 };

src/core/graph/nodes/data/TextureSize.ts

@@ -0,0 +1,29 @@
+import type { NodeDef } from '../../NodeRegistry';
+import { asString } from '../../values';
+import { num } from '../shared';
+
+/**
+ * A picture's own pixel size: a texture, one of its frames or a pixel-art frame, as a sprite wears
+ * it. Written into a sprite's `width` and `height`, the picture shows pixel for pixel – an icon slot
+ * that holds pictures of different sizes stretches none of them. 0 × 0 for no picture.
+ */
+export const TextureSize: NodeDef = {
+  type: 'TextureSize',
+  label: 'Texture size',
+  category: 'data',
+  description: "The picture's own size in pixels, 0 × 0 for none – to show a sprite pixel for pixel.",
+  inputs: [
+    {
+      key: 'texture',
+      label: 'texture',
+      type: 'string',
+      field: { key: 'texture', label: 'Texture', kind: 'texture', default: '' },
+    },
+  ],
+  outputs: [num('width'), num('height')],
+  params: [],
+  read: (_ctx, _params, input, _def, lookup) => {
+    const size = lookup.textureSize(asString(input('texture')));
+    return { width: size?.w ?? 0, height: size?.h ?? 0 };
+  },
+};

src/core/graph/nodes/index.ts

@@ -99,6 +99,7 @@ import { IndexOf } from './data/IndexOf';
 import { ItemAt } from './data/ItemAt';
 import { SetItem } from './data/SetItem';
 import { SubList } from './data/SubList';
+import { TextureSize } from './data/TextureSize';
 import { OnAnimationFinished } from './events/OnAnimationFinished';
 import { OnClick } from './events/OnClick';
 import { OnCollisionEnter } from './events/OnCollisionEnter';
@@ -184,6 +185,7 @@ export const BUILT_IN_NODES: readonly NodeDef[] = [
   IsEnabled,
   Properties,
   GetPosition,
+  TextureSize,
   NumberLiteral,
   BooleanLiteral,
   StringLiteral,

src/core/model/graphLookup.ts

@@ -1,9 +1,11 @@
 import type { GraphLookup } from '../graph/lookup';
 import { startStateOf, statesOf, transitionsOf } from '../graph/stateMachine';
+import { pictureSize } from '../properties/aspect';
 import { resolveAssetProps } from '../properties/resolve';
 import { bagWithoutItemTypes } from './Properties';
 import { typeFields } from './structTypes';
 import { findAssetOf, type Project } from './Project';
+import { resolvePicture } from './texture';
 
 /**
  * What a graph may see of the project around it. A behavior's `defaults` are its variable values;
@@ -36,5 +38,9 @@ export function graphLookup(project: Project): GraphLookup {
       const asset = findAssetOf(project, assetId, 'struct');
       return asset ? { name: asset.name, fields: typeFields(asset).map((f) => f.key) } : null;
     },
+    textureSize: (pictureId) => {
+      const ref = resolvePicture(project, pictureId);
+      return ref ? pictureSize(ref) : null;
+    },
   };
 }

tests/core/node-catalog.test.ts

@@ -265,6 +265,19 @@ const CASES: Record<string, Case[]> = {
       after: (ctx) => expect(ctx.states).toEqual({}),
     },
   ],
+  TextureSize: [
+    {
+      name: "hands out the picture's own pixel size",
+      inputs: { texture: 'coin' },
+      lookup: { ...NO_LOOKUP, textureSize: (id) => (id === 'coin' ? { w: 8, h: 6 } : null) },
+      outputs: { width: 8, height: 6 },
+    },
+    {
+      name: 'no picture is 0 × 0',
+      inputs: { texture: '' },
+      outputs: { width: 0, height: 0 },
+    },
+  ],
   CurrentState: [
     {
       name: 'names the state the machine is in, and hands out its id as well',

tests/core/pixel-art.test.ts

@@ -54,6 +54,7 @@ import {
   withLayerMoved,
   withLayerRemoved,
 } from '../../src/core/model/pixelEdit';
+import { graphLookup } from '../../src/core/model/graphLookup';
 import { findAsset, type Project } from '../../src/core/model/Project';
 import { resolvePicture } from '../../src/core/model/texture';
 import { pictureChoices, textureRefLabel } from '../../src/core/properties/textureRef';
@@ -295,6 +296,23 @@ describe('the picture', () => {
     }
   });
 
+  it('tells a graph its own pixel size, the sheet for the asset and the cut for a frame', () => {
+    const remove = registerPictureSource('pixelart', pixelArtPicture);
+    try {
+      const { project } = makeProject();
+      const asset = art(project);
+      asset.width = 8;
+      asset.height = 6;
+      asset.frames.push({ id: 'second', cels: {} });
+      const lookup = graphLookup(project);
+      expect(lookup.textureSize(asset.id)).toEqual({ w: 16, h: 6 });
+      expect(lookup.textureSize('second')).toEqual({ w: 8, h: 6 });
+      expect(lookup.textureSize('gone')).toBeNull();
+    } finally {
+      remove();
+    }
+  });
+
   it('with one frame is offered as the picture alone', () => {
     const remove = registerPictureSource('pixelart', pixelArtPicture);
     try {