feat: BFS-based left-to-right tree layout for scene graph

editor/components/SceneGraph.vue

@@ -7,6 +7,7 @@ import '@vue-flow/core/dist/style.css'
 import '@vue-flow/controls/dist/style.css'
 import '@vue-flow/core/dist/theme-default.css'
 import type { Connection } from '@vue-flow/core'
+import { computePositions } from '../composables/useLayout'
 
 const props = defineProps<{
   sceneNodes: { id: string; label: string }[]
@@ -25,10 +26,13 @@ const edges = ref<any[]>([])
 const { onNodeClick, onConnect, fitView } = useVueFlow()
 
 function makeNodes() {
-  return props.sceneNodes.map((n, i) => ({
+  const positions = computePositions(props.sceneNodes, props.sceneEdges, props.startScene)
+  return props.sceneNodes.map((n) => {
+    const pos = positions.get(n.id) ?? { x: 0, y: 0 }
+    return {
       id: n.id,
       type: 'default',
-    position: { x: (i % 4) * 220 + 50, y: Math.floor(i / 4) * 120 + 50 },
+      position: pos,
       data: { label: n.id === props.startScene ? `\u25b6 ${n.label}` : n.label },
       style: n.id === props.startScene
         ? { background: '#1b5e20', color: '#fff', borderColor: '#388e3c' }
@@ -38,7 +42,8 @@ function makeNodes() {
       sourcePosition: 'right' as const,
       targetPosition: 'left' as const,
       connectable: true,
-  }))
+    }
+  })
 }
 
 function makeEdges() {

editor/composables/useLayout.ts

@@ -0,0 +1,81 @@
+interface NodeInfo {
+  id: string
+  label: string
+}
+
+interface EdgeInfo {
+  source: string
+  target: string
+}
+
+const H_GAP = 300
+const V_GAP = 140
+const PAD = 60
+
+export function computePositions(
+  nodes: NodeInfo[],
+  edges: EdgeInfo[],
+  startScene: string,
+): Map<string, { x: number; y: number }> {
+  const positions = new Map<string, { x: number; y: number }>()
+
+  const adj = new Map<string, string[]>()
+  for (const n of nodes) adj.set(n.id, [])
+  for (const e of edges) {
+    const list = adj.get(e.source)
+    if (list) list.push(e.target)
+  }
+
+  const level = new Map<string, number>()
+  const visited = new Set<string>()
+  const queue: string[] = []
+
+  if (startScene && adj.has(startScene)) {
+    level.set(startScene, 0)
+    visited.add(startScene)
+    queue.push(startScene)
+  }
+
+  while (queue.length > 0) {
+    const id = queue.shift()!
+    const cur = level.get(id)!
+    for (const t of adj.get(id)!) {
+      if (!visited.has(t)) {
+        visited.add(t)
+        level.set(t, cur + 1)
+        queue.push(t)
+      }
+    }
+  }
+
+  let maxLevel = -1
+  for (const l of level.values()) maxLevel = Math.max(maxLevel, l)
+
+  for (const n of nodes) {
+    if (!level.has(n.id)) {
+      maxLevel++
+      level.set(n.id, maxLevel)
+    }
+  }
+
+  const byLevel = new Map<number, string[]>()
+  for (const [id, lv] of level) {
+    const arr = byLevel.get(lv) || []
+    arr.push(id)
+    byLevel.set(lv, arr)
+  }
+
+  const levels = [...byLevel.entries()].sort((a, b) => a[0] - b[0])
+
+  for (const [lv, ids] of levels) {
+    ids.sort()
+    const count = ids.length
+    for (let i = 0; i < count; i++) {
+      const x = lv * H_GAP + PAD
+      const y = i * V_GAP + PAD
+      positions.set(ids[i], { x, y })
+    }
+  }
+
+  return positions
+}