feat(canvas): add frame name labels for top-level elements

src/canvas/fabric-canvas.tsx

@@ -6,6 +6,7 @@ import { useCanvasViewport } from './use-canvas-viewport'
 import { useCanvasSelection } from './use-canvas-selection'
 import { useCanvasSync } from './use-canvas-sync'
 import { useDimensionLabel } from './use-dimension-label'
+import { useFrameLabels } from './use-frame-labels'
 
 export default function FabricCanvas() {
   const canvasRef = useRef<HTMLCanvasElement>(null)
@@ -18,6 +19,7 @@ export default function FabricCanvas() {
   useCanvasSelection()
   useCanvasSync()
   useDimensionLabel(containerRef)
+  useFrameLabels()
 
   return (
     <div

src/canvas/use-frame-labels.ts

@@ -0,0 +1,64 @@
+import { useEffect } from 'react'
+import { useCanvasStore } from '@/stores/canvas-store'
+import { useDocumentStore } from '@/stores/document-store'
+import type { FabricObjectWithPenId } from './canvas-object-factory'
+
+const LABEL_FONT_SIZE = 12
+const LABEL_OFFSET_Y = 6
+const LABEL_COLOR = '#999999'
+
+export function useFrameLabels() {
+  useEffect(() => {
+    const interval = setInterval(() => {
+      const canvas = useCanvasStore.getState().fabricCanvas
+      if (!canvas) return
+      clearInterval(interval)
+
+      const onAfterRender = () => {
+        const el = canvas.lowerCanvasEl
+        if (!el) return
+        const ctx = el.getContext('2d')
+        if (!ctx) return
+
+        const vpt = canvas.viewportTransform
+        if (!vpt) return
+        const zoom = vpt[0]
+        const dpr = el.width / el.offsetWidth
+
+        const store = useDocumentStore.getState()
+        // Only top-level document children show labels
+        const topIds = new Set(store.document.children.map((c) => c.id))
+        const objects = canvas.getObjects() as FabricObjectWithPenId[]
+
+        ctx.save()
+        const fontSize = LABEL_FONT_SIZE * dpr
+        ctx.font = `500 ${fontSize}px -apple-system, BlinkMacSystemFont, "Segoe UI", sans-serif`
+        ctx.fillStyle = LABEL_COLOR
+
+        for (const obj of objects) {
+          if (!obj.penNodeId) continue
+          if (!topIds.has(obj.penNodeId)) continue
+
+          const node = store.getNodeById(obj.penNodeId)
+          if (!node) continue
+
+          const name = node.name ?? node.type
+          const x = ((obj.left ?? 0) * zoom + vpt[4]) * dpr
+          const y = ((obj.top ?? 0) * zoom + vpt[5]) * dpr
+
+          ctx.fillText(name, x, y - LABEL_OFFSET_Y * dpr)
+        }
+
+        ctx.restore()
+      }
+
+      canvas.on('after:render', onAfterRender)
+
+      return () => {
+        canvas.off('after:render', onAfterRender)
+      }
+    }, 100)
+
+    return () => clearInterval(interval)
+  }, [])
+}