The animation tab's Fit frames the preview, and the separate Centre button is gone (#111)

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

src/editor/AssetTabEditor.ts

@@ -15,11 +15,14 @@ import {
 } from '../ui';
 import type { EditorState } from './state';
 
-/** The canvas each tab wraps: the header's Fit button and the tab's own plumbing need this much. */
+/**
+ * The canvas each tab wraps: the header's Fit button and the tab's own plumbing need this much.
+ * A canvas without `fit` belongs to a tab whose Fit frames something else (see `AssetTabEditor.fit`).
+ */
 export interface TabCanvas {
   readonly currentAssetId: string;
   show(assetId: string): void;
-  fit(): void;
+  fit?(): void;
 }
 
 export interface AssetTabOptions {
@@ -39,6 +42,7 @@ export abstract class AssetTabEditor<
 > extends VStack {
   /** Public for the check scripts. */
   readonly picker: Dropdown;
+  readonly fitButton: Button;
   protected readonly info: Label;
   /** Assigned by `mount`. Public because the check hooks and the play loop reach for it. */
   canvas!: C;
@@ -50,6 +54,7 @@ export abstract class AssetTabEditor<
   ) {
     super();
     this.picker = new Dropdown('—', { width: 200, onClick: () => this.openPicker() });
+    this.fitButton = new Button('Fit', { onClick: () => this.fit() });
     this.info = new Label('', { style: 'small', align: 'right' });
     this.info.minWidth = options.infoWidth;
   }
@@ -63,7 +68,7 @@ export abstract class AssetTabEditor<
     header.add(new Label(this.options.noun, { style: 'muted' }));
     header.add(this.picker);
     for (const widget of extras) header.add(widget);
-    header.add(new Button('Fit', { onClick: () => this.canvas.fit() }));
+    header.add(this.fitButton);
     header.add(new Spacer(), 1);
     header.add(this.info);
 
@@ -103,6 +108,11 @@ export abstract class AssetTabEditor<
     return canvas;
   }
 
+  /** What the header's Fit button frames. Override when the tab has more than one view. */
+  protected fit(): void {
+    this.canvas.fit?.();
+  }
+
   /** Enable/disable whatever `extras` the subclass passed to `mount`. */
   protected syncExtras(_asset: A | null): void {}
 

src/editor/animation/AnimationEditor.ts

@@ -23,7 +23,6 @@ export class AnimationEditor extends AssetTabEditor<AnimationAsset, TimelineCanv
   readonly rootPicker: Dropdown;
   readonly addRowButton: Button;
   readonly playButton: Button;
-  readonly centreButton: Button;
   readonly preview: PreviewCanvas;
 
   constructor(state: EditorState) {
@@ -31,14 +30,18 @@ export class AnimationEditor extends AssetTabEditor<AnimationAsset, TimelineCanv
     this.rootPicker = new Dropdown('—', { width: ROOT_WIDTH, onClick: () => this.openRootPicker() });
     this.addRowButton = new Button('+ Row', { onClick: () => this.openRowDialog() });
     this.playButton = new Button('Play', { width: 64, onClick: () => this.togglePlay() });
-    this.centreButton = new Button('Centre', { onClick: () => this.preview.fit() });
     const timeline = new TimelineCanvas(state);
     this.preview = new PreviewCanvas(state, () => ({
       frame: timeline.playhead,
       reverse: timeline.playheadReverse,
     }));
     timeline.onPlayhead = () => this.preview.redraw();
-    this.mount(timeline, [this.rootPicker, this.addRowButton, this.playButton, this.centreButton]);
+    this.mount(timeline, [this.rootPicker, this.addRowButton, this.playButton]);
+  }
+
+  /** Fit frames the preview; the timeline keeps its own zoom and scroll. */
+  protected override fit(): void {
+    this.preview.fit();
   }
 
   /** The preview above, the timeline below, each taking half. */
@@ -81,7 +84,7 @@ export class AnimationEditor extends AssetTabEditor<AnimationAsset, TimelineCanv
   protected override syncExtras(asset: AnimationAsset | null): void {
     const root = asset ? findAsset(this.state.project, asset.root) : undefined;
     this.preview.show(asset?.id ?? '');
-    this.centreButton.setEnabled(Boolean(root));
+    this.fitButton.setEnabled(Boolean(root));
     this.rootPicker.setText(root ? root.name : asset ? 'Animates…' : '—');
     this.rootPicker.setEnabled(asset !== null);
     // A row needs something to aim at.

src/editor/animation/TimelineCanvas.ts

@@ -131,12 +131,6 @@ export class TimelineCanvas extends Widget {
     return this.assetId;
   }
 
-  /** Back to frame 0 at the default zoom. */
-  fit(): void {
-    this.view = { ...DEFAULT_VIEW };
-    this.redraw();
-  }
-
   get isPlaying(): boolean {
     return this.playingNow;
   }

src/editor/debugHook.ts

@@ -492,7 +492,7 @@ export function installDebugHook(app: Application, state: EditorState, editor: E
         rect: (objectId: string) => editor.animationEditor.preview.objectRect(objectId),
         item: (objectId: string) => editor.animationEditor.preview.itemDrawn(objectId),
         info: () => editor.animationEditor.preview.debugInfo(),
-        centreAt: () => centreOf(editor.animationEditor.centreButton),
+        fitAt: () => centreOf(editor.animationEditor.fitButton),
       },
     },
     container: {