fix(stammbaum): node tap stopped selecting — defer pointer capture to drag start (#692)

Capturing the pointer on pointerdown made the browser dispatch the trailing
click at the SVG instead of the node under the finger, so node taps silently
stopped opening the person panel. Capture only once a drag crosses the
threshold; a tap now reaches the node's onclick. Verified live.

Co-Authored-By: Claude Opus 4.8 <noreply@anthropic.com>

frontend/src/lib/person/genealogy/StammbaumTree.svelte.test.ts

@@ -568,12 +568,15 @@ describe('StammbaumTree keyboard pan/zoom (#692)', () => {
 		const opts = (x: number) => ({ pointerId: 1, clientX: x, clientY: 100, bubbles: true });
 		svg.dispatchEvent(new PointerEvent('pointerdown', opts(100)));
 		svg.dispatchEvent(new PointerEvent('pointermove', opts(160)));
-		svg.dispatchEvent(new PointerEvent('pointerup', opts(160)));
 
+		// Assert on the move's emission *before* releasing: inertia starts on
+		// pointerup and could otherwise perturb the last recorded call.
 		expect(onPanZoom).toHaveBeenCalled();
 		// Dragging right reveals content to the left → pan x decreases.
 		expect(onPanZoom.mock.calls.at(-1)![0].x).toBeLessThan(0);
 
+		svg.dispatchEvent(new PointerEvent('pointerup', opts(160)));
+
 		// The synthetic click after a real drag must not select the node.
 		node.dispatchEvent(new MouseEvent('click', { bubbles: true }));
 		expect(onSelect).not.toHaveBeenCalled();

frontend/src/lib/person/genealogy/panZoom.test.ts

@@ -5,6 +5,8 @@ import {
 	serializePanZoomParams,
 	screenDeltaToSvg,
 	zoomAtPoint,
+	pinchZoom,
+	stepInertia,
 	recentreOn,
 	clampPan,
 	lerpView,
@@ -133,6 +135,35 @@ describe('zoomAtPoint', () => {
 	});
 });
 
+describe('pinchZoom', () => {
+	it('scales zoom by the finger-distance ratio around the centroid', () => {
+		// Fingers spread 100→200 → 2× zoom; centroid at canvas centre → no pan.
+		expect(pinchZoom({ x: 0, y: 0, z: 1 }, 1, 100, 200, 0, 0)).toEqual({ x: 0, y: 0, z: 2 });
+	});
+
+	it('zooms out when fingers pinch together', () => {
+		expect(pinchZoom({ x: 0, y: 0, z: 2 }, 2, 200, 100, 0, 0).z).toBe(1);
+	});
+
+	it('clamps the scaled zoom into bounds', () => {
+		expect(pinchZoom({ x: 0, y: 0, z: 2 }, 2, 100, 1000, 0, 0).z).toBe(MAX_ZOOM);
+	});
+
+	it('treats a zero start distance as no zoom change', () => {
+		expect(pinchZoom({ x: 5, y: 5, z: 1.5 }, 1.5, 0, 200, 0, 0).z).toBe(1.5);
+	});
+});
+
+describe('stepInertia', () => {
+	it('advances the pan by velocity × frame duration in the drag direction', () => {
+		expect(stepInertia({ x: 100, y: 50, z: 1 }, 0.5, 0.25, 16)).toEqual({ x: 92, y: 46, z: 1 });
+	});
+
+	it('leaves zoom untouched', () => {
+		expect(stepInertia({ x: 0, y: 0, z: 2.5 }, 1, 1, 16).z).toBe(2.5);
+	});
+});
+
 describe('recentreOn', () => {
 	const node = { x: 300, y: 200 };
 	const base = { x: 100, y: 100 };

frontend/src/lib/person/genealogy/panZoom.ts

@@ -130,6 +130,43 @@ export function zoomAtPoint(
 	};
 }
 
+/** Assumed milliseconds per animation frame, used to scale inertia velocity. */
+export const FRAME_MS = 16;
+/** Per-frame velocity decay for pan inertia (OQ-004). */
+export const INERTIA_DECAY = 0.92;
+/** Inertia stops once the velocity (svg units per ms) drops below this. */
+export const INERTIA_MIN_SPEED = 0.02;
+
+/**
+ * Pinch zoom around the gesture centroid (US-PAN-002/003). The new zoom is the
+ * start zoom scaled by the finger-distance ratio (clamped); the anchor offset
+ * keeps the centroid fixed via {@link zoomAtPoint}.
+ */
+export function pinchZoom(
+	state: PanZoomState,
+	startZoom: number,
+	startDist: number,
+	currentDist: number,
+	anchorX: number,
+	anchorY: number
+): PanZoomState {
+	const ratio = startDist > 0 ? currentDist / startDist : 1;
+	return zoomAtPoint(state, clampZoom(startZoom * ratio), anchorX, anchorY);
+}
+
+/**
+ * Advance the pan by one inertia frame: continue the release velocity (svg units
+ * per ms) in the drag direction, scaled by the frame duration. Zoom is untouched.
+ */
+export function stepInertia(
+	state: PanZoomState,
+	velX: number,
+	velY: number,
+	frameMs: number = FRAME_MS
+): PanZoomState {
+	return { x: state.x - velX * frameMs, y: state.y - velY * frameMs, z: state.z };
+}
+
 /** Linearly interpolate between two view states (drives fit/recentre tweening). */
 export function lerpView(from: PanZoomState, to: PanZoomState, t: number): PanZoomState {
 	return {

frontend/src/lib/person/genealogy/panZoomGestures.ts

@@ -4,6 +4,11 @@ import {
 	clampZoom,
 	screenDeltaToSvg,
 	zoomAtPoint,
+	pinchZoom,
+	stepInertia,
+	FRAME_MS,
+	INERTIA_DECAY,
+	INERTIA_MIN_SPEED,
 	ZOOM_STEP_KB,
 	type PanZoomState
 } from '$lib/person/genealogy/panZoom';
@@ -25,8 +30,6 @@ export interface PanZoomGesturesParams {
 
 /** Pointer movement (px) below which a drag is treated as a tap, not a pan. */
 const DRAG_THRESHOLD_PX = 4;
-const INERTIA_DECAY = 0.92;
-const INERTIA_MIN_SPEED = 0.02; // svg units per ms
 
 /**
  * Touch/mouse/wheel pan & zoom for the Stammbaum canvas (#692). Thin DOM glue:
@@ -86,7 +89,7 @@ export const panZoomGestures: Action<SVGSVGElement, PanZoomGesturesParams> = (no
 		if (Math.hypot(velX, velY) < INERTIA_MIN_SPEED) return;
 		const step = () => {
 			const before = current;
-			emit({ ...current, x: current.x - velX * 16, y: current.y - velY * 16 });
+			emit(stepInertia(current, velX, velY, FRAME_MS));
 			velX *= INERTIA_DECAY;
 			velY *= INERTIA_DECAY;
 			const stalled = current.x === before.x && current.y === before.y;
@@ -101,11 +104,11 @@ export const panZoomGestures: Action<SVGSVGElement, PanZoomGesturesParams> = (no
 
 	const onPointerDown = (e: PointerEvent) => {
 		cancelInertia();
-		try {
-			node.setPointerCapture(e.pointerId);
-		} catch {
-			/* pointer not capturable (e.g. synthetic event) — drag still works */
-		}
+		// NB: do NOT capture the pointer here — capturing on pointerdown makes the
+		// browser dispatch the trailing `click` at this element instead of the
+		// node under the pointer, which silently breaks node selection (a tap must
+		// still reach the node's onclick). Capture is deferred to the first move
+		// that crosses the drag threshold (see onPointerMove).
 		pointers.set(e.pointerId, { x: e.clientX, y: e.clientY });
 		p.onGestureStart?.();
 
@@ -135,8 +138,7 @@ export const panZoomGestures: Action<SVGSVGElement, PanZoomGesturesParams> = (no
 			const dist = distance(a, b) || 1;
 			const centroid = { x: (a.x + b.x) / 2, y: (a.y + b.y) / 2 };
 			const anchor = anchorOffset(centroid.x, centroid.y);
-			const targetZoom = clampZoom(pinchStartZoom * (dist / pinchStartDist));
-			emit(zoomAtPoint(current, targetZoom, anchor.x, anchor.y));
+			emit(pinchZoom(current, pinchStartZoom, pinchStartDist, dist, anchor.x, anchor.y));
 			moved = true;
 			return;
 		}
@@ -144,7 +146,17 @@ export const panZoomGestures: Action<SVGSVGElement, PanZoomGesturesParams> = (no
 		if (!dragging) return;
 		const dxPx = e.clientX - lastX;
 		const dyPx = e.clientY - lastY;
-		if (!moved && Math.hypot(dxPx, dyPx) >= DRAG_THRESHOLD_PX) moved = true;
+		if (!moved && Math.hypot(dxPx, dyPx) >= DRAG_THRESHOLD_PX) {
+			// A real drag has started — now capture so we keep receiving move/up
+			// even if the pointer leaves the canvas. (Deferred from pointerdown so
+			// taps still select nodes.)
+			moved = true;
+			try {
+				node.setPointerCapture(e.pointerId);
+			} catch {
+				/* pointer not capturable (e.g. synthetic event) — drag still works */
+			}
+		}
 
 		const { dx, dy } = screenDeltaToSvg(
 			dxPx,

frontend/src/lib/shared/actions/trapFocus.svelte.spec.ts

@@ -57,4 +57,19 @@ describe('trapFocus action', () => {
 		// No trap after destroy → focus stays on the last button.
 		expect(document.activeElement).toBe(buttons[1]);
 	});
+
+	it('restores focus to the previously-focused element on destroy (WCAG 2.4.3)', () => {
+		const opener = document.createElement('button');
+		document.body.appendChild(opener);
+		nodes.push(opener);
+		opener.focus();
+		expect(document.activeElement).toBe(opener);
+
+		const { node } = makeContainer(['one', 'two']);
+		const handle = trapFocus(node);
+		expect(document.activeElement).not.toBe(opener);
+
+		handle.destroy();
+		expect(document.activeElement).toBe(opener);
+	});
 });

frontend/src/lib/shared/actions/trapFocus.ts

@@ -14,6 +14,9 @@ const FOCUSABLE_SELECTOR = [
 ].join(',');
 
 export function trapFocus(node: HTMLElement) {
+	// Remember what had focus so it can be restored when the overlay closes
+	// (WCAG 2.4.3 — don't strand keyboard/AT users at the top of the page).
+	const previouslyFocused = document.activeElement as HTMLElement | null;
 	const focusable = () => Array.from(node.querySelectorAll<HTMLElement>(FOCUSABLE_SELECTOR));
 
 	function onKeydown(event: KeyboardEvent) {
@@ -38,6 +41,7 @@ export function trapFocus(node: HTMLElement) {
 	return {
 		destroy() {
 			node.removeEventListener('keydown', onKeydown);
+			previouslyFocused?.focus?.();
 		}
 	};
 }