The tab headers are one TabHeader, the node board and the tile board pan and zoom through one helper, reordering tile pictures and tilemap layers goes through one moveItem, and a tilemap cell is one named type (#85)

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

README.md

@@ -13,8 +13,8 @@ way in.
 ## In one screen
 
 - An **asset** is a named, typed thing (scene, camera, sprite, text, behavior, collider, container,
-  texture, font, sound, animation, state machine, shader, particles, variables) with properties and
-  no position.
+  texture, font, sound, animation, state machine, shader, particles, variables, tile, tilemap) with
+  properties and no position.
 - A **scene object** places an asset: position, sparse **overrides** of its properties, an optional
   parent. Only what differs from the asset is stored; the inspector paints it gold and offers ↺ / ↑.
 - A **container** is a reusable group edited once and placed many times; its content is resolved
@@ -65,6 +65,9 @@ beside it – so locally take the gate plus the step your change touches and lea
 | [Particles](https://git.nockal.com/meleki/game-maker/wiki/Particles) | Particle graphs: a particle as a function of its age |
 | [State machines](https://git.nockal.com/meleki/game-maker/wiki/State-machines) | The asset, named transitions, `State branch`, `Set state` and `State transition` |
 | [Containers](https://git.nockal.com/meleki/game-maker/wiki/Containers) | Templates, instances, screens |
+| [Tiles](https://git.nockal.com/meleki/game-maker/wiki/Tiles) | The tile asset, plain tiles and the two autotile kinds, the pictures as animation steps, the Tile tab |
+| [Tilemaps](https://git.nockal.com/meleki/game-maker/wiki/Tilemaps) | The tilemap asset, painting in the scene view, layers, what it looks like in the game |
+| [Plugins](https://git.nockal.com/meleki/game-maker/wiki/Plugins) | Extending the editor: the plugin file, how it is loaded, switching one on and off, API v1 |
 | [Keyboard](https://git.nockal.com/meleki/game-maker/wiki/Keyboard) | Every shortcut |
 | [Architecture](https://git.nockal.com/meleki/game-maker/wiki/Architecture) | Stack, source layout, the rules that keep it organised |
 | [Development](https://git.nockal.com/meleki/game-maker/wiki/Development) | Commands, the e2e suite, the example games, CI |

src/core/commands/assetCommands.ts

@@ -101,7 +101,7 @@ export interface TextureImage {
  * result, which carries `bytes` and – since original names are kept – a `name` of its own. A
  * spread would put the *file's* name where the asset's belongs and silently overrule the caller.
  */
-export function buildTextureAsset(name: string, image: TextureImage, id = newId()): TextureAsset {
+function buildTextureAsset(name: string, image: TextureImage, id = newId()): TextureAsset {
   return {
     id,
     name,
@@ -147,8 +147,8 @@ export class CreateTextureCommand extends ImportFileCommand<TextureAsset> {
   }
 }
 
-export function buildFontAsset(name: string, file: string, id = newId()): FontAsset {
-  return { id, name, props: defaultsFor('font'), type: 'font', file };
+function buildFontAsset(name: string, file: string): FontAsset {
+  return { id: newId(), name, props: defaultsFor('font'), type: 'font', file };
 }
 
 export class CreateFontCommand extends ImportFileCommand<FontAsset> {
@@ -157,8 +157,8 @@ export class CreateFontCommand extends ImportFileCommand<FontAsset> {
   }
 }
 
-export function buildSoundAsset(name: string, file: string, id = newId()): SoundAsset {
-  return { id, name, props: defaultsFor('sound'), type: 'sound', file };
+function buildSoundAsset(name: string, file: string): SoundAsset {
+  return { id: newId(), name, props: defaultsFor('sound'), type: 'sound', file };
 }
 
 export class CreateSoundCommand extends ImportFileCommand<SoundAsset> {

src/core/commands/require.ts

@@ -57,7 +57,7 @@ export function requireObjectRef(project: Project, holderId: string, objectId: s
  * Rejects an object that only exists because a container template says so. Its structure – what
  * exists, what it is parented to – is the template's business, not the instance's.
  */
-export function requireStructural(project: Project, holder: ObjectTree, objectId: string): void {
+function requireStructural(project: Project, holder: ObjectTree, objectId: string): void {
   if (!isTemplateContent(holder, objectId)) return;
   // Not resolvable at all is a plain "not found", which the caller's own lookup words better.
   const object = objectRef(project, holder, objectId)?.object;

src/core/commands/tileCommands.ts

@@ -5,6 +5,7 @@
  */
 import type { Project } from '../model/Project';
 import { resolvePicture } from '../model/texture';
+import { moveItem } from '../util/list';
 import { type Command, CommandError } from './Command';
 import { requireTile } from './require';
 
@@ -76,12 +77,10 @@ export class MoveTilePictureCommand implements Command {
 
   private move(project: Project, from: number, to: number): void {
     const asset = requireTile(project, this.assetId);
-    const picture = asset.pictures[from];
-    if (picture === undefined) throw new CommandError(`${asset.name} has no picture ${from + 1}`);
-    if (to < 0 || to >= asset.pictures.length)
+    if (asset.pictures[from] === undefined)
+      throw new CommandError(`${asset.name} has no picture ${from + 1}`);
+    if (!moveItem(asset.pictures, from, to))
       throw new CommandError(`${asset.name} has no place ${to + 1} to move it to`);
-    asset.pictures.splice(from, 1);
-    asset.pictures.splice(to, 0, picture);
   }
 }
 

src/core/commands/tilemapCommands.ts

@@ -12,6 +12,8 @@ import { apply } from '../model/matrix';
 import type { Position } from '../model/Properties';
 import type { SceneObject } from '../model/SceneObject';
 import {
+  type Cell,
+  cellAt,
   cellKey,
   edgeCompensation,
   edgeSizeKey,
@@ -26,15 +28,14 @@ import {
 import type { Project } from '../model/Project';
 import { resolveSceneObjectProps } from '../properties/resolve';
 import { localMatrixOf, transformOfObject } from '../properties/transform';
+import { moveItem, type Removed, removeById, removeFirst, restoreAt } from '../util/list';
 import { nextNumberedName } from './naming';
 import { type Command, CommandError } from './Command';
 import { requireTilemap, requireTilemapLayer } from './require';
 import { ObjectEditCommand } from './sceneObjectCommands';
 
 /** One cell as a stroke wants it: `tileId` empty erases. */
-export interface CellEdit {
-  x: number;
-  y: number;
+export interface CellEdit extends Cell {
   tileId: string;
 }
 
@@ -57,7 +58,7 @@ export class PaintTilesCommand implements Command {
 
   /** Nothing to do when every cell already holds what the stroke would write – no empty undo step. */
   static changes(layer: TilemapLayer, edits: readonly CellEdit[]): boolean {
-    return edits.some((edit) => (layer.cells[cellKey(edit.x, edit.y)] ?? '') !== edit.tileId);
+    return edits.some((edit) => cellAt(layer, edit.x, edit.y) !== edit.tileId);
   }
 
   execute(project: Project): void {
@@ -170,15 +171,14 @@ export class AddTilemapLayerCommand implements Command {
 
   undo(project: Project): void {
     const asset = requireTilemap(project, this.assetId);
-    asset.layers = asset.layers.filter((layer) => layer.id !== this.layerId);
+    asset.layers = removeById(asset.layers, this.layerId);
   }
 }
 
 /** Takes a layer out with everything painted on it; the last layer stays, there must be one to paint on. */
 export class RemoveTilemapLayerCommand implements Command {
   readonly label = 'Remove layer';
-  private removed: TilemapLayer | null = null;
-  private index = -1;
+  private removed: Removed<TilemapLayer> | undefined;
 
   constructor(
     private readonly assetId: string,
@@ -188,15 +188,13 @@ export class RemoveTilemapLayerCommand implements Command {
   execute(project: Project): void {
     const asset = requireTilemap(project, this.assetId);
     if (asset.layers.length <= 1) throw new CommandError('A tilemap keeps at least one layer');
-    this.index = asset.layers.findIndex((layer) => layer.id === this.layerId);
-    const layer = asset.layers[this.index];
-    if (!layer) throw new CommandError(`Layer ${this.layerId} not found`);
-    this.removed = layer;
-    asset.layers.splice(this.index, 1);
+    const removed = removeFirst(asset.layers, (layer) => layer.id === this.layerId);
+    if (!removed) throw new CommandError(`Layer ${this.layerId} not found`);
+    this.removed = removed;
   }
 
   undo(project: Project): void {
-    if (this.removed) requireTilemap(project, this.assetId).layers.splice(this.index, 0, this.removed);
+    if (this.removed) restoreAt(requireTilemap(project, this.assetId).layers, [this.removed]);
   }
 }
 
@@ -219,11 +217,8 @@ export class MoveTilemapLayerCommand implements Command {
   }
 
   private move(project: Project, from: number, to: number): void {
-    const asset = requireTilemap(project, this.assetId);
-    const layer = asset.layers[from];
-    if (!layer || to < 0 || to >= asset.layers.length) throw new CommandError('No such layer');
-    asset.layers.splice(from, 1);
-    asset.layers.splice(to, 0, layer);
+    if (!moveItem(requireTilemap(project, this.assetId).layers, from, to))
+      throw new CommandError('No such layer');
   }
 }
 

src/core/model/tile.ts

@@ -26,14 +26,14 @@ export const TILE_COLLISION_SCALE_MIN = 0.1;
 export const TILE_COLLISION_SCALE_MAX = 2;
 
 /** Only the two that make sense for a tile that is always on screen; there is no end to hold. */
-export const TILE_PLAYBACKS = ['loop', 'pingpong'] as const;
+const TILE_PLAYBACKS = ['loop', 'pingpong'] as const;
 export type TilePlayback = (typeof TILE_PLAYBACKS)[number];
 
 /** Quadrant columns of a block: one tile for `none`, two for the autotile blocks. */
-export const BLOCK_COLUMNS: Record<TileKind, number> = { none: 2, floor: 4, wall: 4 };
+const BLOCK_COLUMNS: Record<TileKind, number> = { none: 2, floor: 4, wall: 4 };
 
 /** Quadrant rows of a block: `none` is one tile tall, `floor` three and `wall` two. */
-export const BLOCK_ROWS: Record<TileKind, number> = { none: 2, floor: 6, wall: 4 };
+const BLOCK_ROWS: Record<TileKind, number> = { none: 2, floor: 6, wall: 4 };
 
 export function tileKind(asset: TileAsset): TileKind {
   const value = textOf(asset.props[TILE_KIND_KEY] ?? 'none');

src/core/model/tilemap.ts

@@ -49,11 +49,17 @@ export function tilemapSize(props: PropertyBag): { w: number; h: number } {
   return { w: tilemapColumns(props) * tile, h: tilemapRows(props) * tile };
 }
 
+/** A cell of the grid by column and row; `0,0` is the top-left corner. */
+export interface Cell {
+  x: number;
+  y: number;
+}
+
 export function cellKey(x: number, y: number): string {
   return `${x},${y}`;
 }
 
-export function parseCellKey(key: string): { x: number; y: number } | null {
+export function parseCellKey(key: string): Cell | null {
   const [x, y] = key.split(',').map(Number);
   return Number.isInteger(x) && Number.isInteger(y) ? { x: x as number, y: y as number } : null;
 }
@@ -152,7 +158,7 @@ export function tilemapTileIds(asset: { layers: TilemapLayer[] }): string[] {
  * The cell a point in the tilemap's own frame falls into. The grid is centred on the object's
  * position, as every footprint is, so the top-left corner lies half a map up and to the left.
  */
-export function cellAtPoint(props: PropertyBag, x: number, y: number): { x: number; y: number } {
+export function cellAtPoint(props: PropertyBag, x: number, y: number): Cell {
   const tile = tilemapTileSize(props);
   const { w, h } = tilemapSize(props);
   return { x: Math.floor((x + w / 2) / tile), y: Math.floor((y + h / 2) / tile) };
@@ -214,12 +220,8 @@ export function edgeCompensation(
 }
 
 /** The cells of the rectangle between two corners, both included and clipped to the grid. */
-export function cellsInRect(
-  props: PropertyBag,
-  a: { x: number; y: number },
-  b: { x: number; y: number },
-): { x: number; y: number }[] {
-  const cells: { x: number; y: number }[] = [];
+export function cellsInRect(props: PropertyBag, a: Cell, b: Cell): Cell[] {
+  const cells: Cell[] = [];
   const x0 = Math.max(0, Math.min(a.x, b.x));
   const x1 = Math.min(tilemapColumns(props) - 1, Math.max(a.x, b.x));
   const y0 = Math.max(0, Math.min(a.y, b.y));
@@ -234,12 +236,7 @@ export function cellsInRect(
  * count, or a fill would leak through the gap between two corners. Filling with the tile already
  * there changes nothing, so that returns no cells.
  */
-export function floodFill(
-  props: PropertyBag,
-  layer: TilemapLayer,
-  start: { x: number; y: number },
-  tileId: string,
-): { x: number; y: number }[] {
+export function floodFill(props: PropertyBag, layer: TilemapLayer, start: Cell, tileId: string): Cell[] {
   if (!inGrid(props, start.x, start.y)) return [];
   const from = cellAt(layer, start.x, start.y);
   if (from === tileId) return [];
@@ -269,13 +266,10 @@ export function floodFill(
  * The cells a stroke from one cell to another covers. A pointer jumps between events, so without
  * this a fast drag would paint dots instead of a line.
  */
-export function cellsAlong(
-  from: { x: number; y: number },
-  to: { x: number; y: number },
-): { x: number; y: number }[] {
+export function cellsAlong(from: Cell, to: Cell): Cell[] {
   const steps = Math.max(Math.abs(to.x - from.x), Math.abs(to.y - from.y));
   if (steps === 0) return [{ ...to }];
-  const cells: { x: number; y: number }[] = [];
+  const cells: Cell[] = [];
   for (let i = 1; i <= steps; i++)
     cells.push({
       x: Math.round(from.x + ((to.x - from.x) * i) / steps),

src/core/model/usages.ts

@@ -16,10 +16,7 @@ export interface SceneObjectRef {
   object: SceneObject;
 }
 
-export function objectsWhere(
-  project: Project,
-  predicate: (object: SceneObject) => boolean,
-): SceneObjectRef[] {
+function objectsWhere(project: Project, predicate: (object: SceneObject) => boolean): SceneObjectRef[] {
   const result: SceneObjectRef[] = [];
   for (const holder of objectHolders(project)) {
     for (const object of holder.objects) if (predicate(object)) result.push({ holder, object });

src/core/util/list.ts

@@ -25,6 +25,14 @@ export function restoreAt<T>(list: T[], removed: readonly Removed<T>[]): void {
   for (const entry of [...removed].sort((a, b) => a.index - b.index)) list.splice(entry.index, 0, entry.item);
 }
 
+/** In place; `false` means `from` or `to` is no place in the list, and nothing moved. */
+export function moveItem<T>(list: T[], from: number, to: number): boolean {
+  const inside = (index: number) => Number.isInteger(index) && index >= 0 && index < list.length;
+  if (!inside(from) || !inside(to)) return false;
+  list.splice(to, 0, ...list.splice(from, 1));
+  return true;
+}
+
 /** Returns a new list; unlike the helpers above this one does not mutate. */
 export function removeById<T extends { id: string }>(list: readonly T[], id: string): T[] {
   return list.filter((item) => item.id !== id);

src/editor/AssetTabEditor.ts

@@ -1,19 +1,8 @@
-import { Graphics } from 'pixi.js';
 import type { Asset } from '../core/model/Asset';
 import { findAsset } from '../core/model/Project';
-import {
-  Button,
-  Dropdown,
-  HStack,
-  Label,
-  Menu,
-  type MenuItem,
-  Spacer,
-  Theme,
-  VStack,
-  type Widget,
-} from '../ui';
+import { Button, Dropdown, Label, Menu, type MenuItem, Spacer, VStack, type Widget } from '../ui';
 import type { EditorState } from './state';
+import { TabHeader } from './TabHeader';
 
 /**
  * The canvas each tab wraps: the header's Fit button and the tab's own plumbing need this much.
@@ -46,7 +35,6 @@ export abstract class AssetTabEditor<
   protected readonly info: Label;
   /** Assigned by `mount`. Public because the check hooks and the play loop reach for it. */
   canvas!: C;
-  private readonly headerBg = new Graphics();
 
   constructor(
     protected readonly state: EditorState,
@@ -62,9 +50,7 @@ export abstract class AssetTabEditor<
   /** Builds the header (with `strip` below it) around `canvas`, wires the state events and shows the first asset. */
   protected mount(canvas: C, extras: readonly Widget[] = [], strip?: Widget): void {
     this.canvas = canvas;
-    const header = new HStack({ gap: Theme.gap, padding: Theme.padding, align: 'center' });
-    header.minHeight = Theme.controlHeight + Theme.padding * 2;
-    header.addChildAt(this.headerBg, 0);
+    const header = new TabHeader();
     header.add(new Label(this.options.noun, { style: 'muted' }));
     header.add(this.picker);
     for (const widget of extras) header.add(widget);
@@ -153,12 +139,4 @@ export abstract class AssetTabEditor<
       items.push({ label: `No ${this.options.noun.toLowerCase()}s yet`, onSelect: () => undefined });
     new Menu(items, { searchable: true }).openBelow(this.picker);
   }
-
-  override redraw(): void {
-    super.redraw();
-    this.headerBg.clear();
-    const h = Theme.controlHeight + Theme.padding * 2;
-    this.headerBg.rect(0, 0, this.w, h).fill(Theme.colors.panelHeader);
-    this.headerBg.rect(0, h - 1, this.w, 1).fill(Theme.colors.border);
-  }
 }

src/editor/TabHeader.ts

@@ -0,0 +1,18 @@
+import { Graphics } from 'pixi.js';
+import { HStack, Theme } from '../ui';
+
+/** The bar across the top of a tab: its controls in a row on the header colour, a line below. */
+export class TabHeader extends HStack {
+  private readonly bg = new Graphics();
+
+  constructor() {
+    super({ gap: Theme.gap, padding: Theme.padding, align: 'center' });
+    this.minHeight = Theme.controlHeight + Theme.padding * 2;
+    this.addChildAt(this.bg, 0);
+  }
+
+  override redraw(): void {
+    this.bg.clear().rect(0, 0, this.w, this.h).fill(Theme.colors.panelHeader);
+    this.bg.rect(0, this.h - 1, this.w, 1).fill(Theme.colors.border);
+  }
+}

src/editor/debugHook.ts

@@ -29,7 +29,7 @@ import { currentFontPicker } from './font/FontPicker';
 import { currentNodePalette } from './graph/NodePalette';
 import { currentSoundPicker } from './sound/SoundPicker';
 import { currentImagePicker } from './texture/ImagePicker';
-import { currentTilemapSection } from './panels/TilemapPanel';
+import { currentTilemapWidgets } from './panels/TilemapPanel';
 import type { EditorState, TilemapTool } from './state';
 
 /**
@@ -571,33 +571,33 @@ export function installDebugHook(app: Application, state: EditorState, editor: E
       },
       /** Where the widgets of the painting panel sit: their texts are on screen elsewhere too. */
       toolAt: (tool: string) => {
-        const button = currentTilemapSection()?.tools.get(tool as TilemapTool);
+        const button = currentTilemapWidgets()?.tools.get(tool as TilemapTool);
         return button ? centreOf(button) : null;
       },
       tileButtonAt: (assetId: string) =>
-        currentTilemapSection()?.palette?.swatchGlobal(assetId)?.centre ?? null,
+        currentTilemapWidgets()?.palette?.swatchGlobal(assetId)?.centre ?? null,
       /** A tile's box in the palette: its centre, where its picture sits and the palette's columns (#139). */
       tileSwatch: (assetId: string) => {
-        const palette = currentTilemapSection()?.palette;
+        const palette = currentTilemapWidgets()?.palette;
         const swatch = palette?.swatchGlobal(assetId);
         return palette && swatch ? { ...swatch, columns: palette.columns } : null;
       },
       addLayerAt: () => {
-        const button = currentTilemapSection()?.addLayer;
+        const button = currentTilemapWidgets()?.addLayer;
         return button ? centreOf(button) : null;
       },
       /** The name field of the painted layer and the Show dropdown, with what they hold (#138). */
       layerNameAt: () => {
-        const field = currentTilemapSection()?.layerName;
+        const field = currentTilemapWidgets()?.layerName;
         return field ? { ...centreOf(field), value: field.value } : null;
       },
       focusAt: () => {
-        const button = currentTilemapSection()?.focus;
+        const button = currentTilemapWidgets()?.focus;
         return button ? { ...centreOf(button), label: button.text } : null;
       },
       /** One row of the layer list, top-down as drawn: the layer, its switch and its buttons. */
       layerRowAt: (index: number) => {
-        const row = currentTilemapSection()?.layers[index];
+        const row = currentTilemapWidgets()?.layers[index];
         return row
           ? {
               id: row.id,

src/editor/graph/graphView.ts

@@ -1,11 +1,12 @@
-import type { Graphics } from 'pixi.js';
-import { clamp, drawGrid } from '../../ui';
+import type { Container, FederatedPointerEvent, FederatedWheelEvent, Graphics } from 'pixi.js';
+import { clamp, drawGrid, zoomFactor } from '../../ui';
 import type { Point } from '../framing';
 
 /**
  * What every surface that shows nodes shares with the graph editor: how far it zooms, how the grid
  * is drawn and how the wheel zooms about the pointer. The graph editor and a plugin's node board
- * look and move the same because they both come through here.
+ * look and move the same because they both come through here; the Tile tab's board borrows the
+ * panning and zooming.
  */
 
 /** Spacing of the background grid – and, with snapping on, of the positions a drag can leave. */
@@ -40,6 +41,33 @@ export function zoomedAbout(
   return { pan: { x: at.x - graphX * zoom, y: at.y - graphY * zoom }, zoom };
 }
 
+/**
+ * Drag with any button to pan, wheel to zoom about the pointer – all a board does with the pointer
+ * when its content takes none. `set` receives each new view and which gesture made it.
+ */
+export function panAndZoom(
+  surface: Container,
+  get: () => GraphView,
+  set: (view: GraphView, gesture: 'pan' | 'zoom') => void,
+  limits: { min: number; max: number } = ZOOM_LIMITS,
+): void {
+  let panning: { start: Point; pan: Point } | null = null;
+  surface.on('pointerdown', (e: FederatedPointerEvent) => {
+    panning = { start: { x: e.global.x, y: e.global.y }, pan: { ...get().pan } };
+  });
+  surface.on('globalpointermove', (e: FederatedPointerEvent) => {
+    if (!panning) return;
+    const { start, pan } = panning;
+    set({ ...get(), pan: { x: pan.x + e.global.x - start.x, y: pan.y + e.global.y - start.y } }, 'pan');
+  });
+  surface.on('pointerup', () => (panning = null));
+  surface.on('pointerupoutside', () => (panning = null));
+  surface.on('wheel', (e: FederatedWheelEvent) => {
+    set(zoomedAbout(get(), surface.toLocal(e.global), zoomFactor(e.deltaY), limits), 'zoom');
+    e.preventDefault();
+  });
+}
+
 export function drawGraphGrid(g: Graphics, view: GraphView, w: number, h: number): void {
   g.clear();
   const step = GRID_STEP * view.zoom;

src/editor/panels/TilemapPanel.ts

@@ -14,6 +14,7 @@ import {
   RenameTilemapLayerCommand,
   SetTilemapLayerHiddenCommand,
 } from '../../core/commands/tilemapCommands';
+import type { Command } from '../../core/commands/Command';
 import type { TilemapAsset } from '../../core/model/Asset';
 import { findObject } from '../../core/model/hierarchy';
 import { resolvedHolder } from '../../core/model/instance';
@@ -117,16 +118,16 @@ export function paintedTilemap(state: EditorState): { objectId: string; asset: T
  */
 export function paintedLayerId(state: EditorState, asset: TilemapAsset): string {
   const chosen = state.tilemapPaint.layerId;
-  if (asset.layers.some((layer) => layer.id === chosen)) return chosen;
+  if (findLayer(asset, chosen)) return chosen;
   return asset.layers[asset.layers.length - 1]?.id ?? '';
 }
 
 /**
- * The widgets of the section as they were last built. Every one of them carries an icon or a name
+ * The widgets of the panel as they were last built. Every one of them carries an icon or a name
  * that is on screen elsewhere too – the tile's row in the asset panel, the layer's name – so a
  * check cannot find them by their text; this is what it clicks instead.
  */
-export interface TilemapSectionWidgets {
+export interface TilemapPanelWidgets {
   tools: Map<TilemapTool, Button>;
   /** Null while the project has no tile. */
   palette: TilePalette | null;
@@ -138,10 +139,10 @@ export interface TilemapSectionWidgets {
   addLayer: Button;
 }
 
-let built: TilemapSectionWidgets | null = null;
+let built: TilemapPanelWidgets | null = null;
 
 /** Null while the panel has no tilemap to paint, so a check cannot click a widget that is gone. */
-export function currentTilemapSection(): TilemapSectionWidgets | null {
+export function currentTilemapWidgets(): TilemapPanelWidgets | null {
   return built;
 }
 
@@ -225,13 +226,13 @@ export class TilemapPanel extends Panel {
     built = null;
     this.title = target ? `Tilemap · ${target.asset.name}` : 'Tilemap';
     this.setTitle(this.title);
-    if (target) buildTilemapSection(this.host, target.asset);
+    if (target) buildPanelContent(this.host, target.asset);
     this.scroll.setContent(this.host.body);
     this.onTargetChange();
   }
 }
 
-function buildTilemapSection(host: InspectorHost, asset: TilemapAsset): void {
+function buildPanelContent(host: InspectorHost, asset: TilemapAsset): void {
   const { state } = host;
   const paint = state.tilemapPaint;
   const painted = paintedLayerId(state, asset);
@@ -253,7 +254,7 @@ function buildTilemapSection(host: InspectorHost, asset: TilemapAsset): void {
         })),
       ).openBelow(focus),
   });
-  const widgets: TilemapSectionWidgets = {
+  const widgets: TilemapPanelWidgets = {
     tools: new Map(),
     palette: null,
     layers: [],
@@ -312,24 +313,11 @@ function buildTilemapSection(host: InspectorHost, asset: TilemapAsset): void {
     });
     choose.toggled = layer.id === painted;
     row.add(choose, 1);
-    const up = new Button('↑', {
-      variant: 'ghost',
-      width: 24,
-      onClick: () => state.execute(new MoveTilemapLayerCommand(asset.id, index, index + 1)),
-    });
-    const down = new Button('↓', {
-      variant: 'ghost',
-      width: 24,
-      onClick: () => state.execute(new MoveTilemapLayerCommand(asset.id, index, index - 1)),
-    });
-    const remove = new Button('✕', {
-      variant: 'ghost',
-      width: 24,
-      onClick: () => state.execute(new RemoveTilemapLayerCommand(asset.id, layer.id)),
-    });
-    row.add(up);
-    row.add(down);
-    row.add(remove);
+    const small = (label: string, command: () => Command) =>
+      row.add(new Button(label, { variant: 'ghost', width: 24, onClick: () => state.execute(command()) }));
+    const up = small('↑', () => new MoveTilemapLayerCommand(asset.id, index, index + 1));
+    const down = small('↓', () => new MoveTilemapLayerCommand(asset.id, index, index - 1));
+    const remove = small('✕', () => new RemoveTilemapLayerCommand(asset.id, layer.id));
     widgets.layers.push({ id: layer.id, name: choose, visible, up, down, remove });
     host.body.add(row);
   }
@@ -351,7 +339,7 @@ function tileIdsOf(state: EditorState): string[] {
 }
 
 /**
- * What the section is built from, for the panel's rebuild check: the layers, the tiles on offer
+ * What the panel is built from, for its rebuild check: the layers, the tiles on offer
  * and what is painted with. The cells themselves are deliberately absent – a stroke must not
  * rebuild the panel under the pointer that is drawing it – and so are the tiles' pictures and
  * names, which the palette repaints by itself.

src/editor/plugins/NodeBoard.ts

@@ -1,9 +1,10 @@
-import { Container, type FederatedPointerEvent, type FederatedWheelEvent, Graphics } from 'pixi.js';
+import { Container, Graphics } from 'pixi.js';
 import type { NodeDef } from '../../core/graph';
-import { Button, HStack, Label, type Size, Spacer, Theme, VStack, Widget, zoomFactor } from '../../ui';
+import { Button, Label, type Size, Spacer, Theme, VStack, Widget } from '../../ui';
 import { type Box, frameBoxes } from '../framing';
-import { drawGraphGrid, FIT_MARGIN, type GraphView, ZOOM_LIMITS, zoomedAbout } from '../graph/graphView';
+import { drawGraphGrid, FIT_MARGIN, type GraphView, panAndZoom, ZOOM_LIMITS } from '../graph/graphView';
 import { NodeView } from '../graph/NodeView';
+import { TabHeader } from '../TabHeader';
 
 /** One node as a plugin hands it over: a title at a position in graph units. */
 export interface BoardNode {
@@ -50,7 +51,6 @@ class BoardCanvas extends Widget {
   private readonly layer = new Container();
   private readonly views: NodeView[] = [];
   private view: GraphView = { pan: { x: 0, y: 0 }, zoom: 1 };
-  private panning: { start: { x: number; y: number }; pan: { x: number; y: number } } | null = null;
   /** Framed once there is a size and something to frame; after that the view is the user's. */
   private needsFit = true;
 
@@ -59,22 +59,14 @@ class BoardCanvas extends Widget {
     this.layer.eventMode = 'none';
     this.addChild(this.bg, this.grid, this.layer, this.clip);
     this.layer.mask = this.clip;
-    this.on('pointerdown', (e: FederatedPointerEvent) => {
-      this.panning = { start: { x: e.global.x, y: e.global.y }, pan: { ...this.view.pan } };
-    });
-    this.on('globalpointermove', (e: FederatedPointerEvent) => {
-      if (!this.panning) return;
-      const { start, pan } = this.panning;
-      this.view.pan = { x: pan.x + e.global.x - start.x, y: pan.y + e.global.y - start.y };
+    panAndZoom(
+      this,
+      () => this.view,
+      (view) => {
+        this.view = view;
         this.applyView();
-    });
-    this.on('pointerup', () => (this.panning = null));
-    this.on('pointerupoutside', () => (this.panning = null));
-    this.on('wheel', (e: FederatedWheelEvent) => {
-      this.view = zoomedAbout(this.view, this.toLocal(e.global), zoomFactor(e.deltaY));
-      this.applyView();
-      e.preventDefault();
-    });
+      },
+    );
   }
 
   setNodes(nodes: readonly BoardNode[]): void {
@@ -138,14 +130,11 @@ export class NodeBoard extends VStack {
   readonly fitButton: Button;
   private readonly canvas = new BoardCanvas();
   private readonly count = new Label('', { style: 'small', align: 'right' });
-  private readonly headerBg = new Graphics();
 
   constructor() {
     super();
     this.fitButton = new Button('Fit', { onClick: () => this.fit() });
-    const header = new HStack({ gap: Theme.gap, padding: Theme.padding, align: 'center' });
-    header.minHeight = Theme.controlHeight + Theme.padding * 2;
-    header.addChildAt(this.headerBg, 0);
+    const header = new TabHeader();
     header.add(this.fitButton);
     header.add(new Spacer(), 1);
     header.add(this.count);
@@ -169,12 +158,4 @@ export class NodeBoard extends VStack {
   debugInfo(): ReturnType<BoardCanvas['debugInfo']> {
     return this.canvas.debugInfo();
   }
-
-  override redraw(): void {
-    super.redraw();
-    const h = Theme.controlHeight + Theme.padding * 2;
-    this.headerBg.clear();
-    this.headerBg.rect(0, 0, this.w, h).fill(Theme.colors.panelHeader);
-    this.headerBg.rect(0, h - 1, this.w, 1).fill(Theme.colors.border);
-  }
 }

src/editor/plugins/PluginsPane.ts

@@ -1,5 +1,5 @@
-import { Graphics } from 'pixi.js';
 import { Checkbox, HStack, Label, ScrollContainer, Spacer, Theme, VStack } from '../../ui';
+import { TabHeader } from '../TabHeader';
 import type { PluginManager, PluginRecord } from './loader';
 
 const NAME_WIDTH = 200;
@@ -65,7 +65,6 @@ class PluginRow extends HStack {
  * reading a name out of it would mean running it.
  */
 export class PluginsPane extends VStack {
-  private readonly headerBg = new Graphics();
   private readonly hint: Label;
   private readonly rows = new VStack();
   private readonly scroll = new ScrollContainer();
@@ -75,9 +74,7 @@ export class PluginsPane extends VStack {
 
   constructor() {
     super();
-    const header = new HStack({ gap: Theme.gap, padding: Theme.padding, align: 'center' });
-    header.minHeight = Theme.controlHeight + Theme.padding * 2;
-    header.addChildAt(this.headerBg, 0);
+    const header = new TabHeader();
     header.add(new Label('Plugins', { style: 'bodyBold' }));
     header.add(new Spacer(Theme.padding));
     this.hint = new Label('', { style: 'small' });
@@ -154,12 +151,4 @@ export class PluginsPane extends VStack {
     this.scroll.relayoutContent();
     this.relayout();
   }
-
-  override redraw(): void {
-    super.redraw();
-    const h = Theme.controlHeight + Theme.padding * 2;
-    this.headerBg.clear();
-    this.headerBg.rect(0, 0, this.w, h).fill(Theme.colors.panelHeader);
-    this.headerBg.rect(0, h - 1, this.w, 1).fill(Theme.colors.border);
-  }
 }

src/editor/state.ts

@@ -59,7 +59,7 @@ export type ListSlot = { field?: string } & (
   | { kind: 'node'; assetId: string; nodeId: string; key: string }
 );
 
-export function sameSlot(a: ListSlot | null, b: ListSlot | null): boolean {
+function sameSlot(a: ListSlot | null, b: ListSlot | null): boolean {
   if (!a || !b) return a === b;
   if (a.field !== b.field) return false;
   switch (a.kind) {

src/editor/tile/TileCanvas.ts

@@ -1,11 +1,4 @@
-import {
-  Container,
-  type FederatedPointerEvent,
-  type FederatedWheelEvent,
-  Graphics,
-  Sprite,
-  Text,
-} from 'pixi.js';
+import { Container, Graphics, Sprite, Text } from 'pixi.js';
 import type { TileAsset } from '../../core/model/Asset';
 import {
   autotileCombinations,
@@ -26,10 +19,10 @@ import {
   tilePlayback,
 } from '../../core/model/tile';
 import { findAssetOf } from '../../core/model/Project';
-import { type Size, Theme, textStyle, Widget, zoomFactor } from '../../ui';
+import { type Size, Theme, textStyle, Widget } from '../../ui';
 import { textureLibrary } from '../../viewport/TextureLibrary';
 import { type Box, frameBoxes } from '../framing';
-import { type GraphView, zoomedAbout } from '../graph/graphView';
+import { type GraphView, panAndZoom } from '../graph/graphView';
 import type { EditorState } from '../state';
 
 /** Tiles per row in the combination grid; 47 of them then read as six rows of eight. */
@@ -66,7 +59,6 @@ export class TileCanvas extends Widget {
   private readonly tiles: BoardTile[] = [];
   private readonly labels: Text[] = [];
   private view: GraphView = { pan: { x: 0, y: 0 }, zoom: 1 };
-  private panning: { start: { x: number; y: number }; pan: { x: number; y: number } } | null = null;
   private assetId = '';
   /** Seconds the preview has been running – the only thing that moves without an edit. */
   private time = 0;
@@ -84,23 +76,16 @@ export class TileCanvas extends Widget {
     this.addChild(this.bg, this.content, this.hint, this.clip);
     this.content.mask = this.clip;
 
-    this.on('pointerdown', (e: FederatedPointerEvent) => {
-      this.panning = { start: { x: e.global.x, y: e.global.y }, pan: { ...this.view.pan } };
-    });
-    this.on('globalpointermove', (e: FederatedPointerEvent) => {
-      if (!this.panning) return;
-      const { start, pan } = this.panning;
-      this.view.pan = { x: pan.x + e.global.x - start.x, y: pan.y + e.global.y - start.y };
+    panAndZoom(
+      this,
+      () => this.view,
+      (view, gesture) => {
+        this.view = view;
+        if (gesture === 'zoom') this.needsFit = false;
         this.applyView();
-    });
-    this.on('pointerup', () => (this.panning = null));
-    this.on('pointerupoutside', () => (this.panning = null));
-    this.on('wheel', (e: FederatedWheelEvent) => {
-      this.view = zoomedAbout(this.view, this.toLocal(e.global), zoomFactor(e.deltaY), ZOOM_LIMITS);
-      this.needsFit = false;
-      this.applyView();
-      e.preventDefault();
-    });
+      },
+      ZOOM_LIMITS,
+    );
 
     state.on('project', () => this.redraw());
     state.on('load', () => this.show(''));

tests/core/list.test.ts

@@ -1,5 +1,5 @@
 import { describe, expect, it } from 'vitest';
-import { removeById, removeFirst, restoreAt } from '../../src/core/util/list';
+import { moveItem, removeById, removeFirst, restoreAt } from '../../src/core/util/list';
 
 const items = () => [{ id: 'a' }, { id: 'b' }, { id: 'c' }];
 
@@ -30,6 +30,35 @@ describe('removeFirst', () => {
   });
 });
 
+describe('moveItem', () => {
+  const ids = (list: { id: string }[]) => list.map((i) => i.id);
+
+  it('moves forwards and backwards, and the reverse move restores the order', () => {
+    const list = items();
+    expect(moveItem(list, 0, 2)).toBe(true);
+    expect(ids(list)).toEqual(['b', 'c', 'a']);
+    expect(moveItem(list, 2, 0)).toBe(true);
+    expect(ids(list)).toEqual(['a', 'b', 'c']);
+    moveItem(list, 2, 1);
+    expect(ids(list)).toEqual(['a', 'c', 'b']);
+  });
+
+  it('refuses a place outside the list or between two places and leaves the list as it was', () => {
+    for (const [from, to] of [
+      [-1, 0],
+      [3, 0],
+      [0, -1],
+      [0, 3],
+      [0.5, 1],
+      [0, 1.5],
+    ] as const) {
+      const list = items();
+      expect(moveItem(list, from, to)).toBe(false);
+      expect(ids(list)).toEqual(['a', 'b', 'c']);
+    }
+  });
+});
+
 describe('removeById', () => {
   it('returns a new list without that item and does not mutate the old one', () => {
     const list = items();