feuerwerk/tests/core/tilemap.test.ts

import { describe, expect, it } from 'vitest';
import {
  CreateAssetCommand,
  CreateTextureCommand,
  SetAssetPropertyCommand,
} from '../../src/core/commands/assetCommands';
import { AddTilePictureCommand } from '../../src/core/commands/tileCommands';
import {
  AddTilemapLayerCommand,
  DuplicateTilemapLayerCommand,
  MoveTilemapLayerCommand,
  PaintTilesCommand,
  paintTiles,
  RemoveTilemapLayerCommand,
  RenameTilemapLayerCommand,
  SetTilemapLayerHiddenCommand,
  SetTilemapLayerZCommand,
} from '../../src/core/commands/tilemapCommands';
import type { TilemapAsset } from '../../src/core/model/Asset';
import { isPlaceableType } from '../../src/core/model/AssetTypes';
import { TILE_KIND_KEY, type TileKind } from '../../src/core/model/tile';
import { findAsset, type Project } from '../../src/core/model/Project';
import {
  cellAt,
  cellAtPoint,
  cellKey,
  cellOrigin,
  cellsAlong,
  cellsInRect,
  floodFill,
  inGrid,
  layerTiles,
  neighboursOf,
  TILEMAP_COLUMNS_KEY,
  TILEMAP_ROWS_KEY,
  TILEMAP_TILE_KEY,
  tilemapTileIds,
  tilemapSize,
} from '../../src/core/model/tilemap';
import { tilemapsUsing } from '../../src/core/model/usages';
import { DIMMED_LAYER_ALPHA, layerAlpha } from '../../src/viewport/tilemap';
import { groupByTile, tileMesh } from '../../src/viewport/tilemapMesh';
import { makeProject, roundTrip } from '../helpers';

const FILE = `${'a1b2c3d4'.repeat(8)}.png`;

/** A tilemap with a floor autotile to paint with, both sized like the RPG-Maker sheets. */
function makeTilemap(kind: TileKind = 'floor') {
  const fixture = makeProject();
  const texture = new CreateTextureCommand('Outside', {
    file: FILE,
    width: 96,
    height: kind === 'floor' ? 144 : 96,
  });
  fixture.stack.execute(texture);
  const tile = new CreateAssetCommand('tile', 'Grass');
  fixture.stack.execute(tile);
  fixture.stack.execute(new SetAssetPropertyCommand(tile.asset.id, TILE_KIND_KEY, kind));
  fixture.stack.execute(new AddTilePictureCommand(tile.asset.id, texture.asset.id));
  const tilemap = new CreateAssetCommand('tilemap', 'Ground');
  fixture.stack.execute(tilemap);
  const assetOf = () => findAsset(fixture.project, tilemap.asset.id) as TilemapAsset;
  return {
    ...fixture,
    tileId: tile.asset.id,
    tilemapId: tilemap.asset.id,
    assetOf,
    layerId: () => assetOf().layers[0]!.id,
    paint: (cells: { x: number; y: number }[], tileId = tile.asset.id) =>
      fixture.stack.execute(
        new PaintTilesCommand(
          tilemap.asset.id,
          assetOf().layers[0]!.id,
          cells.map((at) => ({ ...at, tileId })),
        ),
      ),
  };
}

function cellsOf(project: Project, assetId: string): Record<string, string> {
  const asset = findAsset(project, assetId) as TilemapAsset;
  return asset.layers[0]!.cells;
}

describe('the tilemap asset', () => {
  it('is placed, unlike the tiles it draws with', () => {
    expect(isPlaceableType('tilemap')).toBe(true);
    expect(isPlaceableType('tile')).toBe(false);
  });

  it('starts with one layer and no cells', () => {
    const f = makeTilemap();
    expect(f.assetOf().layers).toHaveLength(1);
    expect(f.assetOf().layers[0]!.cells).toEqual({});
  });

  it('is as big as its grid says, centred on its position', () => {
    const f = makeTilemap();
    const props = f.assetOf().props;
    expect(tilemapSize(props)).toEqual({ w: 20 * 48, h: 15 * 48 });
    expect(cellOrigin(props, 0, 0)).toEqual({ x: -480, y: -360 });
    // The centre of the map is the corner of the four middle cells.
    expect(cellAtPoint(props, 0, 0)).toEqual({ x: 10, y: 7 });
    expect(cellAtPoint(props, -480, -360)).toEqual({ x: 0, y: 0 });
    expect(cellAtPoint(props, -1, -1)).toEqual({ x: 9, y: 7 });
  });

  it('follows the grid and the cell size when they change', () => {
    const f = makeTilemap();
    f.stack.execute(new SetAssetPropertyCommand(f.tilemapId, TILEMAP_COLUMNS_KEY, 4));
    f.stack.execute(new SetAssetPropertyCommand(f.tilemapId, TILEMAP_ROWS_KEY, 3));
    f.stack.execute(new SetAssetPropertyCommand(f.tilemapId, TILEMAP_TILE_KEY, 10));
    expect(tilemapSize(f.assetOf().props)).toEqual({ w: 40, h: 30 });
    expect(inGrid(f.assetOf().props, 3, 2)).toBe(true);
    expect(inGrid(f.assetOf().props, 4, 2)).toBe(false);
    expect(inGrid(f.assetOf().props, -1, 0)).toBe(false);
  });
});

describe('painting a tilemap', () => {
  it('paints, erases and takes both back as one step', () => {
    const f = makeTilemap();
    f.paint([
      { x: 1, y: 1 },
      { x: 2, y: 1 },
    ]);
    expect(cellsOf(f.project, f.tilemapId)).toEqual({ '1,1': f.tileId, '2,1': f.tileId });
    f.stack.execute(new PaintTilesCommand(f.tilemapId, f.layerId(), [{ x: 1, y: 1, tileId: '' }]));
    expect(cellsOf(f.project, f.tilemapId)).toEqual({ '2,1': f.tileId });
    f.stack.undo();
    expect(cellsOf(f.project, f.tilemapId)).toEqual({ '1,1': f.tileId, '2,1': f.tileId });
    f.stack.undo();
    expect(cellsOf(f.project, f.tilemapId)).toEqual({});
  });

  it('puts back what a stroke painted over, not merely empty', () => {
    const f = makeTilemap();
    const other = new CreateAssetCommand('tile', 'Sand');
    f.stack.execute(other);
    f.paint([{ x: 3, y: 3 }]);
    f.paint([{ x: 3, y: 3 }], other.asset.id);
    expect(cellAt(f.assetOf().layers[0]!, 3, 3)).toBe(other.asset.id);
    f.stack.undo();
    expect(cellAt(f.assetOf().layers[0]!, 3, 3)).toBe(f.tileId);
  });

  it('knows when a stroke would change nothing', () => {
    const f = makeTilemap();
    f.paint([{ x: 0, y: 0 }]);
    const layer = f.assetOf().layers[0]!;
    expect(PaintTilesCommand.changes(layer, [{ x: 0, y: 0, tileId: f.tileId }])).toBe(false);
    expect(PaintTilesCommand.changes(layer, [{ x: 0, y: 0, tileId: '' }])).toBe(true);
    expect(PaintTilesCommand.changes(layer, [{ x: 5, y: 5, tileId: f.tileId }])).toBe(true);
  });

  it('makes no undo step for a rectangle over cells that already hold its tile', () => {
    const f = makeTilemap();
    const box = cellsInRect(f.assetOf().props, { x: 0, y: 0 }, { x: 2, y: 2 });
    f.paint(box);
    const again = box.map((at) => ({ ...at, tileId: f.tileId }));
    expect(paintTiles(f.assetOf().layers[0]!, f.tilemapId, again)).toBeNull();
    // The one undo left takes back the first rectangle, not an empty second one.
    f.stack.undo();
    expect(cellsOf(f.project, f.tilemapId)).toEqual({});
  });

  it('still makes one when a single cell of the rectangle changes', () => {
    const f = makeTilemap();
    f.paint(cellsInRect(f.assetOf().props, { x: 0, y: 0 }, { x: 1, y: 1 }));
    const wider = cellsInRect(f.assetOf().props, { x: 0, y: 0 }, { x: 2, y: 1 });
    const command = paintTiles(
      f.assetOf().layers[0]!,
      f.tilemapId,
      wider.map((at) => ({ ...at, tileId: f.tileId })),
    );
    expect(command).not.toBeNull();
    f.stack.execute(command!);
    expect(Object.keys(cellsOf(f.project, f.tilemapId))).toHaveLength(6);
    f.stack.undo();
    expect(Object.keys(cellsOf(f.project, f.tilemapId)).sort()).toEqual(['0,0', '0,1', '1,0', '1,1']);
  });

  it('makes no undo step for a fill that finds nothing to fill', () => {
    const f = makeTilemap();
    f.paint([{ x: 0, y: 0 }]);
    const layer = f.assetOf().layers[0]!;
    expect(floodFill(f.assetOf().props, layer, { x: 0, y: 0 }, f.tileId)).toEqual([]);
    expect(paintTiles(layer, f.tilemapId, [])).toBeNull();
  });

  it('covers the cells between two pointer events', () => {
    expect(cellsAlong({ x: 0, y: 0 }, { x: 3, y: 0 })).toEqual([
      { x: 1, y: 0 },
      { x: 2, y: 0 },
      { x: 3, y: 0 },
    ]);
    expect(cellsAlong({ x: 0, y: 0 }, { x: 2, y: 2 })).toEqual([
      { x: 1, y: 1 },
      { x: 2, y: 2 },
    ]);
    expect(cellsAlong({ x: 4, y: 2 }, { x: 4, y: 2 })).toEqual([{ x: 4, y: 2 }]);
  });

  it('clips a rectangle to the grid', () => {
    const f = makeTilemap();
    f.stack.execute(new SetAssetPropertyCommand(f.tilemapId, TILEMAP_COLUMNS_KEY, 3));
    f.stack.execute(new SetAssetPropertyCommand(f.tilemapId, TILEMAP_ROWS_KEY, 2));
    const cells = cellsInRect(f.assetOf().props, { x: -2, y: 1 }, { x: 9, y: 9 });
    expect(cells).toEqual([
      { x: 0, y: 1 },
      { x: 1, y: 1 },
      { x: 2, y: 1 },
    ]);
  });
});

describe('what a painted cell shows', () => {
  it('joins only cells holding the same tile', () => {
    const f = makeTilemap();
    const other = new CreateAssetCommand('tile', 'Sand');
    f.stack.execute(other);
    f.paint([
      { x: 5, y: 5 },
      { x: 6, y: 5 },
    ]);
    f.paint([{ x: 5, y: 4 }], other.asset.id);
    const layer = f.assetOf().layers[0]!;
    const props = f.assetOf().props;
    const around = neighboursOf(props, layer, 5, 5, f.tileId);
    expect(around.e).toBe(true);
    // The cell above holds a *different* tile, so this one closes against it.
    expect(around.n).toBe(false);
    expect(around.w).toBe(false);
  });

  it('counts anything outside the grid as empty', () => {
    const f = makeTilemap();
    f.stack.execute(new SetAssetPropertyCommand(f.tilemapId, TILEMAP_COLUMNS_KEY, 2));
    f.stack.execute(new SetAssetPropertyCommand(f.tilemapId, TILEMAP_ROWS_KEY, 2));
    f.paint([
      { x: 0, y: 0 },
      { x: 1, y: 0 },
      { x: 0, y: 1 },
      { x: 1, y: 1 },
    ]);
    const asset = f.assetOf();
    const around = neighboursOf(asset.props, asset.layers[0]!, 1, 1, f.tileId);
    expect(around.n).toBe(true);
    expect(around.w).toBe(true);
    expect(around.e).toBe(false);
    expect(around.s).toBe(false);
  });

  it('gives a lone cell the four convex corners and a joined one the inside', () => {
    const f = makeTilemap();
    f.paint([{ x: 2, y: 2 }]);
    const asset = f.assetOf();
    const lone = layerTiles(f.project, asset.props, asset.layers[0]!)[0]!;
    // The block's convex corners, as `FLOOR_CORNERS` names them.
    expect(lone.quadrants).toEqual([
      { x: 0, y: 2 },
      { x: 3, y: 2 },
      { x: 0, y: 5 },
      { x: 3, y: 5 },
    ]);
    f.paint([
      { x: 1, y: 1 },
      { x: 2, y: 1 },
      { x: 3, y: 1 },
      { x: 1, y: 2 },
      { x: 3, y: 2 },
      { x: 1, y: 3 },
      { x: 2, y: 3 },
      { x: 3, y: 3 },
    ]);
    const after = layerTiles(f.project, f.assetOf().props, f.assetOf().layers[0]!);
    const middle = after.find((tile) => tile.x === 2 && tile.y === 2)!;
    expect(middle.quadrants).toEqual([
      { x: 2, y: 4 },
      { x: 1, y: 4 },
      { x: 2, y: 3 },
      { x: 1, y: 3 },
    ]);
  });

  it('draws a plain tile the same in every cell, whatever lies around it', () => {
    const f = makeTilemap('none');
    f.paint([
      { x: 1, y: 1 },
      { x: 2, y: 1 },
      { x: 1, y: 2 },
      { x: 5, y: 5 },
    ]);
    const asset = f.assetOf();
    const tiles = layerTiles(f.project, asset.props, asset.layers[0]!);
    expect(tiles).toHaveLength(4);
    for (const tile of tiles)
      expect(tile.quadrants).toEqual([
        { x: 0, y: 0 },
        { x: 1, y: 0 },
        { x: 0, y: 1 },
        { x: 1, y: 1 },
      ]);
  });

  it('leaves out cells outside the grid and cells naming nothing', () => {
    const f = makeTilemap();
    f.stack.execute(new SetAssetPropertyCommand(f.tilemapId, TILEMAP_COLUMNS_KEY, 2));
    f.stack.execute(new SetAssetPropertyCommand(f.tilemapId, TILEMAP_ROWS_KEY, 2));
    f.paint([
      { x: 0, y: 0 },
      { x: 5, y: 0 },
    ]);
    f.stack.execute(new PaintTilesCommand(f.tilemapId, f.layerId(), [{ x: 1, y: 1, tileId: 'gone' }]));
    const asset = f.assetOf();
    const tiles = layerTiles(f.project, asset.props, asset.layers[0]!);
    expect(tiles.map((t) => `${t.x},${t.y}`)).toEqual(['0,0']);
    // The cell naming a deleted tile is kept in the model – an undo may bring it back.
    expect(asset.layers[0]!.cells[cellKey(1, 1)]).toBe('gone');
  });

  it('reads the same tiles twice, in reading order', () => {
    const f = makeTilemap();
    f.paint([
      { x: 4, y: 2 },
      { x: 1, y: 1 },
      { x: 2, y: 1 },
    ]);
    const asset = f.assetOf();
    const order = layerTiles(f.project, asset.props, asset.layers[0]!).map((t) => `${t.x},${t.y}`);
    expect(order).toEqual(['1,1', '2,1', '4,2']);
  });
});

describe('the layers of a tilemap', () => {
  it('adds, renames, reorders, hides and removes, each with an undo', () => {
    const f = makeTilemap();
    const add = new AddTilemapLayerCommand(f.tilemapId);
    f.stack.execute(add);
    expect(f.assetOf().layers.map((l) => l.name)).toEqual(['Layer 1', 'Layer 2']);

    f.stack.execute(new RenameTilemapLayerCommand(f.tilemapId, add.layerId, 'Roofs'));
    expect(f.assetOf().layers[1]!.name).toBe('Roofs');

    f.stack.execute(new MoveTilemapLayerCommand(f.tilemapId, 1, 0));
    expect(f.assetOf().layers.map((l) => l.name)).toEqual(['Roofs', 'Layer 1']);
    f.stack.undo();
    expect(f.assetOf().layers.map((l) => l.name)).toEqual(['Layer 1', 'Roofs']);

    f.stack.execute(new SetTilemapLayerHiddenCommand(f.tilemapId, add.layerId, true));
    expect(f.assetOf().layers[1]!.hidden).toBe(true);
    f.stack.undo();
    expect(f.assetOf().layers[1]!.hidden).toBeUndefined();

    f.stack.execute(new RemoveTilemapLayerCommand(f.tilemapId, add.layerId));
    expect(f.assetOf().layers).toHaveLength(1);
    f.stack.undo();
    expect(f.assetOf().layers.map((l) => l.name)).toEqual(['Layer 1', 'Roofs']);
  });

  it('duplicates a layer right above it, with its cells, its z and a name of its own', () => {
    const f = makeTilemap();
    f.paint([{ x: 1, y: 1 }]);
    f.stack.execute(new SetTilemapLayerZCommand(f.tilemapId, f.layerId(), 3));
    f.stack.execute(new AddTilemapLayerCommand(f.tilemapId));
    const copy = new DuplicateTilemapLayerCommand(f.tilemapId, f.layerId());
    f.stack.execute(copy);
    const layers = f.assetOf().layers;
    expect(layers.map((l) => l.name)).toEqual(['Layer 1', 'Layer 1 copy', 'Layer 2']);
    expect(layers[1]).toMatchObject({ id: copy.layerId, z: 3, cells: layers[0]!.cells });
    // Cells of its own: painting on the copy leaves the original alone.
    f.stack.execute(new PaintTilesCommand(f.tilemapId, copy.layerId, [{ x: 1, y: 1, tileId: '' }]));
    expect(f.assetOf().layers[0]!.cells[cellKey(1, 1)]).toBeTruthy();

    f.stack.undo();
    f.stack.undo();
    expect(f.assetOf().layers.map((l) => l.name)).toEqual(['Layer 1', 'Layer 2']);
  });

  it('renames a layer without the spaces around it, refuses a blank name and undoes to the old one', () => {
    const f = makeTilemap();
    f.stack.execute(new RenameTilemapLayerCommand(f.tilemapId, f.layerId(), '  Ground  '));
    expect(f.assetOf().layers[0]!.name).toBe('Ground');
    expect(() => f.stack.execute(new RenameTilemapLayerCommand(f.tilemapId, f.layerId(), '   '))).toThrow(
      'A layer needs a name',
    );
    expect(f.assetOf().layers[0]!.name).toBe('Ground');
    f.stack.undo();
    expect(f.assetOf().layers[0]!.name).toBe('Layer 1');
  });

  it('keeps the last layer, because there has to be one to paint on', () => {
    const f = makeTilemap();
    expect(() => f.stack.execute(new RemoveTilemapLayerCommand(f.tilemapId, f.layerId()))).toThrow(
      'A tilemap keeps at least one layer',
    );
    expect(f.assetOf().layers).toHaveLength(1);
  });

  it('takes the cells of a removed layer with it and brings them back', () => {
    const f = makeTilemap();
    const add = new AddTilemapLayerCommand(f.tilemapId);
    f.stack.execute(add);
    f.stack.execute(new PaintTilesCommand(f.tilemapId, add.layerId, [{ x: 2, y: 2, tileId: f.tileId }]));
    f.stack.execute(new RemoveTilemapLayerCommand(f.tilemapId, add.layerId));
    expect(f.assetOf().layers).toHaveLength(1);
    f.stack.undo();
    expect(f.assetOf().layers[1]!.cells).toEqual({ '2,2': f.tileId });
  });
});

describe('how the scene view shows the layers next to the painted one', () => {
  it('draws all of them whole, fades the others or leaves them out', () => {
    expect(layerAlpha('a', null)).toBe(1);
    expect(layerAlpha('b', { layerId: 'a', mode: 'all' })).toBe(1);
    expect(layerAlpha('a', { layerId: 'a', mode: 'dim' })).toBe(1);
    expect(layerAlpha('b', { layerId: 'a', mode: 'dim' })).toBe(DIMMED_LAYER_ALPHA);
    expect(layerAlpha('a', { layerId: 'a', mode: 'solo' })).toBe(1);
    expect(layerAlpha('b', { layerId: 'a', mode: 'solo' })).toBe(0);
  });
});

describe('a tilemap in the document', () => {
  it('survives a round trip with its layers and cells', () => {
    const f = makeTilemap();
    const add = new AddTilemapLayerCommand(f.tilemapId);
    f.stack.execute(add);
    f.stack.execute(new SetTilemapLayerHiddenCommand(f.tilemapId, add.layerId, true));
    f.paint([{ x: 1, y: 2 }]);
    const back = roundTrip(f.project);
    const asset = findAsset(back, f.tilemapId) as TilemapAsset;
    expect(asset.layers).toHaveLength(2);
    expect(asset.layers[0]!.cells).toEqual({ '1,2': f.tileId });
    expect(asset.layers[1]!.hidden).toBe(true);
  });

  it('drops cells that are not a pair of whole numbers, and doubled layers', () => {
    const f = makeTilemap();
    const asset = f.assetOf();
    asset.layers[0]!.cells['nonsense'] = f.tileId;
    asset.layers[0]!.cells['1.5,2'] = f.tileId;
    asset.layers[0]!.cells['3,3'] = f.tileId;
    asset.layers.push({ ...asset.layers[0]!, name: 'Twin' });
    const back = findAsset(roundTrip(f.project), f.tilemapId) as TilemapAsset;
    expect(back.layers).toHaveLength(1);
    expect(back.layers[0]!.cells).toEqual({ '3,3': f.tileId });
  });

  it('counts as a use of the tiles painted on it', () => {
    const f = makeTilemap();
    expect(tilemapsUsing(f.project, [f.tileId])).toHaveLength(0);
    f.paint([{ x: 0, y: 0 }]);
    expect(tilemapsUsing(f.project, [f.tileId]).map((a) => a.id)).toEqual([f.tilemapId]);
    expect(tilemapTileIds(f.assetOf())).toEqual([f.tileId]);
  });
});

describe('the mesh a layer becomes', () => {
  const sheet = { quad: 24, block: { x: 0, y: 0, w: 96, h: 144 }, textureWidth: 96, textureHeight: 144 };

  it('is one mesh per tile, not one per cell', () => {
    const f = makeTilemap();
    const other = new CreateAssetCommand('tile', 'Sand');
    f.stack.execute(other);
    f.paint([
      { x: 0, y: 0 },
      { x: 1, y: 0 },
      { x: 2, y: 0 },
    ]);
    f.paint([{ x: 4, y: 0 }], other.asset.id);
    const asset = f.assetOf();
    const groups = groupByTile(layerTiles(f.project, asset.props, asset.layers[0]!));
    expect(groups.size).toBe(2);
    expect(groups.get(f.tileId)).toHaveLength(3);
  });

  it('builds four quads per cell, at the cell it belongs to', () => {
    const tiles = [
      {
        x: 1,
        y: 0,
        tileId: 'a',
        quadrants: [
          { x: 0, y: 0 },
          { x: 1, y: 0 },
          { x: 0, y: 1 },
          { x: 1, y: 1 },
        ] as [
          { x: number; y: number },
          { x: number; y: number },
          { x: number; y: number },
          { x: number; y: number },
        ],
      },
    ];
    const { positions, uvs, indices } = tileMesh(tiles, 48, { x: 0, y: 0 }, { ...sheet, smooth: false });
    expect(positions).toHaveLength(4 * 4 * 2);
    expect(indices).toHaveLength(4 * 6);
    // The cell starts at x = 48, and its top-left quarter is 24 wide.
    expect([positions[0], positions[1]]).toEqual([48, 0]);
    expect([positions[2], positions[3]]).toEqual([72, 0]);
    // Quadrant (0, 0) of a 96 × 144 sheet cut into 24 px quarters is the first quarter of the uvs.
    expect(uvs[0]).toBeCloseTo(0, 3);
    expect(uvs[1]).toBeCloseTo(0, 3);
    expect(uvs[2]).toBeCloseTo(24 / 96, 3);
    expect(uvs[3]).toBeCloseTo(0, 3);
  });

  it('pulls the uvs half a texel in when the picture is sampled smoothly', () => {
    const tiles = [
      {
        x: 0,
        y: 0,
        tileId: 'a',
        quadrants: [
          { x: 0, y: 0 },
          { x: 0, y: 0 },
          { x: 0, y: 0 },
          { x: 0, y: 0 },
        ] as [
          { x: number; y: number },
          { x: number; y: number },
          { x: number; y: number },
          { x: number; y: number },
        ],
      },
    ];
    const hard = tileMesh(tiles, 48, { x: 0, y: 0 }, { ...sheet, smooth: false });
    const soft = tileMesh(tiles, 48, { x: 0, y: 0 }, { ...sheet, smooth: true });
    expect(hard.uvs[0]).toBeCloseTo(0.02 / 96, 6);
    expect(soft.uvs[0]).toBeCloseTo(0.5 / 96, 6);
    // The positions are untouched: only what is sampled moves, never where it lands.
    expect([...soft.positions]).toEqual([...hard.positions]);
  });

  it('keeps nearest uvs a sliver inside the quarter so odd zooms never pick the neighbour', () => {
    const tiles = [
      {
        x: 0,
        y: 0,
        tileId: 'a',
        quadrants: [
          { x: 1, y: 1 },
          { x: 1, y: 1 },
          { x: 1, y: 1 },
          { x: 1, y: 1 },
        ] as [
          { x: number; y: number },
          { x: number; y: number },
          { x: number; y: number },
          { x: number; y: number },
        ],
      },
    ];
    const { uvs } = tileMesh(tiles, 48, { x: 0, y: 0 }, { ...sheet, smooth: false });
    // Quarter (1, 1) spans texels 24..48 on both axes. Every corner sits strictly inside it,
    // but by far less than half a texel, so the texel picked at any pixel centre stays the same.
    const us = [uvs[0]!, uvs[2]!, uvs[4]!, uvs[6]!].map((u) => u * 96);
    const vs = [uvs[1]!, uvs[3]!, uvs[5]!, uvs[7]!].map((v) => v * 144);
    for (const t of [...us, ...vs]) {
      expect(t).toBeGreaterThan(24);
      expect(t).toBeLessThan(48);
      expect(Math.min(t - 24, 48 - t)).toBeLessThan(0.05);
    }
  });
});