fix(primitives): flow renders visibly by default and its declared events fire

- pane fills its parent instead of collapsing to the 0px strip every
  consumer debugged as a data bug; background/viewport/panel get a
  default stacking triple (0/1/2) so chrome no longer paints over nodes
- nodeClick/edgeClick/paneClick were declared in FlowRootEmits but never
  emitted — wired for real; nodeDoubleClick synthesized in the drag
  layer (it already tells clicks from drags), and dblclick-zoom ignores
  [data-flow-node] so opening a node no longer also zooms the canvas
- FlowEdge.label was typed but never rendered — the default edge now
  draws a haloed midpoint label, and label joins the v-memo keys so
  edits are not frozen by the memo
- fitViewOnMount prop fits once nodes AND the pane are measured (either
  can finish first), skipped when the viewport is controlled

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>

vue/primitives/src/canvas/flow/FlowBackground.vue

@@ -54,7 +54,7 @@ const linePath = computed(() => {
   <svg
     data-flow-background=""
     :data-variant="variant"
-    :style="{ position: 'absolute', inset: '0', width: '100%', height: '100%', pointerEvents: 'none', color }"
+    :style="{ position: 'absolute', inset: '0', width: '100%', height: '100%', pointerEvents: 'none', zIndex: 0, color }"
   >
     <pattern
       :id="patternId"

vue/primitives/src/canvas/flow/FlowEdge.vue

@@ -134,13 +134,14 @@ function onPointerdown(event: PointerEvent): void {
   if (event.button !== 0 || edge.value?.selectable === false || !ctx.elementsSelectable.value) return;
   event.stopPropagation();
   ctx.selectEdge(id, event.shiftKey || event.metaKey || event.ctrlKey);
+  ctx.emitEdgeClick(id, event);
 }
 </script>
 
 <template>
   <g
     v-if="endpoints"
-    v-memo="[path[0], selected, edge?.animated, edge?.selectable, edge?.data, markerStartRef, markerEndRef]"
+    v-memo="[path[0], selected, edge?.animated, edge?.selectable, edge?.data, edge?.label, markerStartRef, markerEndRef]"
     data-flow-edge=""
     :data-id="id"
     :data-type="resolvedType"
@@ -176,6 +177,21 @@ function onPointerdown(event: PointerEvent): void {
         :style="interactionPathStyle"
         @pointerdown="onPointerdown"
       />
+      <!-- The halo (paint-order + stroke) keeps the text legible over the
+           path and the background without the consumer styling anything. -->
+      <text
+        v-if="edge?.label"
+        data-flow-edge-label=""
+        :x="path[1]"
+        :y="path[2]"
+        text-anchor="middle"
+        dominant-baseline="middle"
+        fill="currentColor"
+        stroke="var(--flow-edge-label-halo, white)"
+        stroke-width="3"
+        paint-order="stroke"
+        :style="{ pointerEvents: 'none', fontSize: '12px' }"
+      >{{ edge.label }}</text>
     </template>
   </g>
 </template>

vue/primitives/src/canvas/flow/FlowPane.vue

@@ -65,8 +65,10 @@ useKeyboard(currentElement, ctx, useViewportApi(ctx));
 
 useEventListener(currentElement, 'click', (event: MouseEvent) => {
   const target = event.target as Element | null;
-  if (target && !target.closest('[data-flow-node],[data-flow-edge]'))
+  if (target && !target.closest('[data-flow-node],[data-flow-edge]')) {
     ctx.clearSelection();
+    ctx.emitPaneClick(event as PointerEvent);
+  }
 });
 </script>
 
@@ -79,7 +81,16 @@ useEventListener(currentElement, 'click', (event: MouseEvent) => {
     :data-interactive="ctx.interactive.value ? '' : undefined"
     :role="ctx.disableKeyboardA11y.value ? undefined : 'application'"
     :tabindex="ctx.disableKeyboardA11y.value ? undefined : 0"
-    :style="{ position: 'relative', overflow: 'hidden', touchAction: 'none' }"
+    :style="{
+      position: 'relative',
+      overflow: 'hidden',
+      touchAction: 'none',
+      // Everything inside is absolutely positioned, so content-sizing always
+      // collapsed to 0×N and the graph rendered into an invisible strip.
+      // Vue merges a consumer's style attr over this, so it stays overridable.
+      width: '100%',
+      height: '100%',
+    }"
   >
     <slot />
 

vue/primitives/src/canvas/flow/FlowPanel.vue

@@ -28,7 +28,9 @@ const { forwardRef } = useForwardExpose();
 
 const style = computed<CSSProperties>(() => {
   const [v, h] = position.split('-') as ['top' | 'bottom', 'left' | 'center' | 'right'];
-  const s: CSSProperties = { position: 'absolute', pointerEvents: 'all' };
+  // Above the viewport's explicit layer (zIndex 1): a positioned sibling
+  // with z-index auto would otherwise paint underneath the graph.
+  const s: CSSProperties = { position: 'absolute', pointerEvents: 'all', zIndex: 2 };
   s[v] = '0';
   if (h === 'center') {
     s.left = '50%';

vue/primitives/src/canvas/flow/FlowRoot.vue

@@ -73,6 +73,14 @@ export interface FlowRootProps extends PrimitiveProps {
   isValidConnection?: IsValidConnection;
   /** Cull nodes/edges outside the viewport — for large graphs. @default false */
   onlyRenderVisibleElements?: boolean;
+  /**
+   * Frame the whole graph once after the initial nodes are measured. Skipped
+   * when an explicit `viewport` / `defaultViewport` is provided — a restored
+   * viewport must not be stomped by a fit. With virtualization the fit uses
+   * whatever is measured plus declared node sizes; fully unmeasured nodes are
+   * framed by position alone. @default false
+   */
+  fitViewOnMount?: boolean | FitViewParams;
   /** Extra px kept rendered around the viewport when virtualizing. @default 200 */
   virtualizationBuffer?: number;
 }
@@ -87,12 +95,13 @@ export interface FlowRootEmits {
   selectionChange: [selection: { nodes: string[]; edges: string[] }];
   paneClick: [event: PointerEvent];
   nodeClick: [id: string, event: PointerEvent];
+  nodeDoubleClick: [id: string, event: PointerEvent];
   edgeClick: [id: string, event: PointerEvent];
 }
 </script>
 
 <script setup lang="ts">
-import { computed, shallowRef, toRef, triggerRef, useSlots, watch } from 'vue';
+import { computed, getCurrentInstance, shallowRef, toRef, triggerRef, useSlots, watch } from 'vue';
 import { useId } from '@robonen/vue';
 import FlowPane from './FlowPane.vue';
 import FlowViewport from './FlowViewport.vue';
@@ -124,6 +133,7 @@ const {
   disableKeyboardA11y = false,
   isValidConnection,
   onlyRenderVisibleElements = false,
+  fitViewOnMount = false,
   virtualizationBuffer = 200,
   as = 'div',
 } = defineProps<FlowRootProps>();
@@ -330,6 +340,7 @@ function setNodeMeasured(id: string, size: Dimensions, handleBounds: InternalNod
   // pick up the fresh measurement / handle geometry.
   map.set(id, { ...n, measured: sizeChanged ? size : n.measured, handleBounds });
   triggerRef(nodeLookup);
+  maybeFitOnMount();
 }
 
 function updateNode(id: string, patch: Partial<FlowNode>): void {
@@ -515,12 +526,56 @@ const context: FlowContext = {
   endConnection,
   emitNodesChange: changes => emit('nodesChange', changes),
   emitEdgesChange: changes => emit('edgesChange', changes),
+  emitNodeClick: (id, event) => emit('nodeClick', id, event),
+  emitNodeDoubleClick: (id, event) => emit('nodeDoubleClick', id, event),
+  emitEdgeClick: (id, event) => emit('edgeClick', id, event),
+  emitPaneClick: event => emit('paneClick', event),
 };
 provideFlowContext(context);
 
 // Imperative API, also exposed so consumers can drive the flow via a template ref.
 const api = useViewportApi(context);
 
+// ── fitViewOnMount ────────────────────────────────────────────────────────
+// A viewport the consumer controls (v-model:viewport) or seeds
+// (defaultViewport) is restored state; a fit must never stomp it. Model
+// getters fall back to a local default, so controlledness is read off the
+// vnode, not the value.
+const vnodeProps = getCurrentInstance()?.vnode.props ?? {};
+let fitOnMountPending = fitViewOnMount !== false
+  && defaultViewport === undefined
+  && !('viewport' in vnodeProps)
+  && !('onUpdate:viewport' in vnodeProps);
+
+/**
+ * Armed until it fires once: waits for every RENDERED node to report a
+ * measurement — fitting to unmeasured nodes fits to nothing. Under
+ * virtualization only the rendered subset ever measures; the rest contribute
+ * their declared or positional bounds through `fitView` itself.
+ */
+function maybeFitOnMount(): void {
+  if (!fitOnMountPending) return;
+
+  // Nodes can finish measuring before the pane has a size (or the reverse);
+  // the shot must not burn against a 0×0 container, so both gates hold it and
+  // the pane-rect watcher below re-arms the attempt.
+  const rect = paneRect.value;
+  if (rect.width === 0 || rect.height === 0) return;
+
+  const map = nodeLookup.value;
+  if (map.size === 0) return;
+
+  for (const id of visibleNodeIds.value) {
+    const n = map.get(id);
+    if (n && n.measured.width === 0 && n.measured.height === 0) return;
+  }
+
+  fitOnMountPending = false;
+  api.fitView(typeof fitViewOnMount === 'object' ? fitViewOnMount : undefined);
+}
+
+watch(paneRect, maybeFitOnMount);
+
 const nodeSlotNames = computed(() => Object.keys(slots).filter(n => n === 'node' || n.startsWith('node-')));
 const edgeSlotNames = computed(() => Object.keys(slots).filter(n => n === 'edge' || n.startsWith('edge-')));
 

vue/primitives/src/canvas/flow/FlowViewport.vue

@@ -42,6 +42,9 @@ const transform = computed(() => {
       left: '0',
       width: '100%',
       height: '100%',
+      // The slot (background, panels) renders after this element; explicit
+      // layers keep the graph above the background and below the chrome.
+      zIndex: 1,
       transformOrigin: '0 0',
       transform,
       willChange: ctx.isInteracting.value ? 'transform' : undefined,

vue/primitives/src/canvas/flow/__test__/Fixes.test.ts

@@ -0,0 +1,191 @@
+import type { VueWrapper } from '@vue/test-utils';
+import type { FlowEdge, FlowNode } from '../index';
+import { mount } from '@vue/test-utils';
+import { afterEach, describe, expect, it, vi } from 'vitest';
+import { h, nextTick } from 'vue';
+import { FlowBackground, FlowPanel, FlowRoot } from '../index';
+
+/**
+ * Regressions found by building a real story-map consumer: the pane rendered
+ * into zero area, the background painted over the graph, edge labels never
+ * rendered, the declared click emits never fired, and dblclick on a node
+ * zoomed the canvas. Each test pins the fixed contract.
+ */
+
+const wrappers: Array<VueWrapper<any>> = [];
+afterEach(() => {
+  while (wrappers.length) wrappers.pop()!.unmount();
+  document.body.innerHTML = '';
+});
+function track<T extends VueWrapper<any>>(w: T): T {
+  wrappers.push(w);
+  return w;
+}
+
+const nodes: FlowNode[] = [
+  { id: 'a', position: { x: 0, y: 0 } },
+  { id: 'b', position: { x: 300, y: 200 } },
+];
+
+function pointer(el: Element, type: string, x = 10, y = 10) {
+  el.dispatchEvent(new PointerEvent(type, { button: 0, pointerId: 1, clientX: x, clientY: y, bubbles: true, cancelable: true }));
+}
+
+/** The pane sizes to its parent; give the test-utils wrapper a real box. */
+function sizeWrapper(w: VueWrapper<any>, width = 600, height = 400) {
+  const el = w.element as HTMLElement;
+  el.style.width = `${width}px`;
+  el.style.height = `${height}px`;
+}
+
+const edges: FlowEdge[] = [
+  { id: 'a-b', source: 'a', target: 'b', label: 'take me' },
+];
+
+function flow(props: Record<string, unknown> = {}, slots: Record<string, unknown> = {}) {
+  return track(mount(FlowRoot, {
+    attachTo: document.body,
+    props: { defaultNodes: nodes, defaultEdges: edges, ...props },
+    slots: { 'node-default': () => h('div', { style: 'width:120px;height:40px' }, 'n'), ...slots },
+  }));
+}
+
+describe('pane sizing', () => {
+  it('fills its parent instead of collapsing to zero height', () => {
+    const w = flow();
+    sizeWrapper(w);
+
+    const pane = w.find('[data-flow-pane]').element as HTMLElement;
+
+    // All pane content is absolutely positioned; without an own height the
+    // whole graph rendered inside an invisible 0px strip.
+    expect(pane.clientHeight).toBe(400);
+  });
+});
+
+describe('stacking', () => {
+  it('layers background under the graph and panels above it', () => {
+    const w = flow({}, {
+      default: () => [h(FlowBackground), h(FlowPanel, { position: 'top-right' }, () => 'p')],
+    });
+
+    const viewport = (w.find('[data-flow-viewport]').element as HTMLElement).style.zIndex;
+    const background = (w.find('[data-flow-background]').element as HTMLElement).style.zIndex;
+    const panel = (w.find('[data-flow-panel]').element as HTMLElement).style.zIndex;
+
+    // The slot chrome renders AFTER the viewport in DOM order; without these
+    // layers the background dots painted over every node.
+    expect(Number(background)).toBeLessThan(Number(viewport));
+    expect(Number(panel)).toBeGreaterThan(Number(viewport));
+  });
+});
+
+describe('edge labels', () => {
+  it('renders the label the type always promised', async () => {
+    const w = flow();
+    await nextTick();
+
+    const label = w.find('[data-flow-edge-label]');
+
+    expect(label.exists()).toBe(true);
+    expect(label.text()).toBe('take me');
+  });
+
+  it('renders no label element when there is none', async () => {
+    const w = flow({ defaultEdges: [{ id: 'a-b', source: 'a', target: 'b' }] });
+    await nextTick();
+
+    expect(w.find('[data-flow-edge-label]').exists()).toBe(false);
+  });
+});
+
+describe('the click family', () => {
+  async function settle(w: VueWrapper<any>, selector: string, times = 1, gap = 50) {
+    const el = w.find(selector).element;
+
+    for (let index = 0; index < times; index++) {
+      pointer(el, 'pointerdown');
+      pointer(el, 'pointerup');
+      await nextTick();
+      if (gap)
+        await new Promise(resolve => setTimeout(resolve, gap));
+    }
+  }
+
+  it('emits nodeClick for a settled click', async () => {
+    const w = flow();
+    await nextTick();
+
+    await settle(w, '[data-flow-node][data-id="a"]');
+
+    expect(w.emitted('nodeClick')?.[0]?.[0]).toBe('a');
+  });
+
+  it('pairs two settled clicks into nodeDoubleClick', async () => {
+    const w = flow();
+    await nextTick();
+
+    await settle(w, '[data-flow-node][data-id="a"]', 2, 40);
+
+    expect(w.emitted('nodeDoubleClick')?.[0]?.[0]).toBe('a');
+  });
+
+  it('emits paneClick only for background clicks', async () => {
+    const w = flow();
+    await nextTick();
+
+    await w.find('[data-flow-pane]').trigger('click');
+    expect(w.emitted('paneClick')).toHaveLength(1);
+
+    await w.find('[data-flow-node][data-id="a"] div').trigger('click');
+    expect(w.emitted('paneClick')).toHaveLength(1);
+  });
+
+  it('emits edgeClick when the edge is picked', async () => {
+    const w = flow();
+    await nextTick();
+
+    pointer(w.findAll('[data-flow-edge] path')[1]!.element, 'pointerdown');
+    await nextTick();
+
+    expect(w.emitted('edgeClick')?.[0]?.[0]).toBe('a-b');
+  });
+
+  it('does not zoom on a node double click', async () => {
+    const w = flow();
+    await nextTick();
+
+    const before = (w.find('[data-flow-viewport]').element as HTMLElement).style.transform;
+    await w.find('[data-flow-node][data-id="a"]').trigger('dblclick');
+    await nextTick();
+
+    // The gesture belongs to the node (nodeDoubleClick), not the camera.
+    expect((w.find('[data-flow-viewport]').element as HTMLElement).style.transform).toBe(before);
+  });
+});
+
+describe('fitViewOnMount', () => {
+  it('frames the graph once nodes are measured', async () => {
+    const w = flow({ fitViewOnMount: true });
+    sizeWrapper(w);
+
+    await vi.waitFor(() => {
+      const t = (w.find('[data-flow-viewport]').element as HTMLElement).style.transform;
+      expect(t).not.toBe('translate(0px, 0px) scale(1)');
+    });
+  });
+
+  it('never stomps a consumer-controlled viewport', async () => {
+    const w = flow({
+      fitViewOnMount: true,
+      viewport: { x: 17, y: 23, zoom: 1.5 },
+      'onUpdate:viewport': () => {},
+    });
+
+    await new Promise(resolve => setTimeout(resolve, 120));
+
+    // A bound viewport is restored state; the fit must skip it entirely.
+    expect((w.find('[data-flow-viewport]').element as HTMLElement).style.transform)
+      .toBe('translate(17px, 23px) scale(1.5)');
+  });
+});

vue/primitives/src/canvas/flow/composables/useNodeDrag.ts

@@ -35,6 +35,9 @@ export interface NodeDragOptions {
 /** Elements inside a node that must not initiate a drag. */
 const NO_DRAG_SELECTOR = 'input, textarea, select, button, [contenteditable="true"], [data-handleid], .nodrag';
 
+/** Two settled clicks within this window read as a double click. */
+const DOUBLE_CLICK_MS = 350;
+
 /**
  * Pointer-capture node drag. Moves the node (and every co-selected node) by the
  * pointer delta converted to flow space (`delta / zoom`), optionally snapped to
@@ -57,6 +60,7 @@ export function useNodeDrag(
   let startX = 0;
   let startY = 0;
   let started = false;
+  let lastClickAt = 0;
   let lastX = 0;
   let lastY = 0;
   let rafId: number | null = null;
@@ -150,6 +154,26 @@ export function useNodeDrag(
     if (started) {
       flush();
       ctx.commitNodeDrag();
+      lastClickAt = 0;
+    }
+    else if (snapshot.size > 0) {
+      // The pointer never crossed the drag threshold: this is a click. The
+      // pane cannot see it (propagation stopped on pointerdown), so the node
+      // is the only place that can report it — and pair two settled clicks
+      // into a double click.
+      const id = toValue(nodeId);
+
+      ctx.emitNodeClick(id, event);
+
+      const now = event.timeStamp;
+
+      if (now - lastClickAt <= DOUBLE_CLICK_MS) {
+        ctx.emitNodeDoubleClick(id, event);
+        lastClickAt = 0;
+      }
+      else {
+        lastClickAt = now;
+      }
     }
     pointerId = -1;
     started = false;

vue/primitives/src/canvas/flow/composables/usePanZoom.ts

@@ -158,7 +158,9 @@ export function usePanZoom(
   // ── double-click zoom ──────────────────────────────────────────────────────
   useEventListener(target, 'dblclick', (event: MouseEvent) => {
     if (!zoomOnDoubleClick || !ctx.interactive.value) return;
-    if (event.target instanceof Element && event.target.closest('.nopan')) return;
+    // A double click on a node belongs to the node (nodeDoubleClick), not
+    // to the zoom gesture.
+    if (event.target instanceof Element && event.target.closest('.nopan, [data-flow-node]')) return;
     const vp = current();
     const newZoom = clampZoom(vp.zoom * doubleClickZoomFactor, ctx.minZoom.value, ctx.maxZoom.value);
     if (newZoom === vp.zoom) return;

vue/primitives/src/canvas/flow/context.ts

@@ -121,6 +121,10 @@ export interface FlowContext {
   // ── change emission ──────────────────────────────────────────────────────
   emitNodesChange: (changes: NodeChange[]) => void;
   emitEdgesChange: (changes: EdgeChange[]) => void;
+  emitNodeClick: (id: string, event: PointerEvent) => void;
+  emitNodeDoubleClick: (id: string, event: PointerEvent) => void;
+  emitEdgeClick: (id: string, event: PointerEvent) => void;
+  emitPaneClick: (event: PointerEvent) => void;
 }
 
 const flow = useContextFactory<FlowContext>('FlowContext');