UI④:元素盘点击落子真能落 —— 原型里这条路是坏的

事件流实测:click → drag.init → create.start → create.move → **create.rejected**。
create.move 要有 hover 目标才算 canExecute,而 click 到达时鼠标早已抬起,
拖拽在同一个调用栈里就被拒 —— 工具提示写着「点击后点画布落子」,一颗子也落不下。
点击这条路改为直接 modeling.createShape 到空位(撞车往下让、一列满换列);
拖拽那条路不动。实测:落子 32→33、追加自动连线 33→34、撤销回退干净。

Co-Authored-By: Claude Fable 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01KeDBx2PHLavbURXB8LJJ7m

apps/web/src/shared/gov/flow/flow-editor-core.ts

@@ -441,36 +441,92 @@ export const PALETTE_SPECS: Array<{ key: string; label: string; className: strin
 ];
 
 class FlowPalette {
-  static $inject = ["palette", "create", "elementFactory", "elementRegistry", "flowEditorConfig"];
+  static $inject = ["palette", "create", "elementFactory", "elementRegistry", "flowEditorConfig", "modeling", "canvas"];
 
   private _create: Any;
   private _elementFactory: Any;
   private _elementRegistry: Any;
   private _config: Any;
+  private _modeling: Any;
+  private _canvas: Any;
 
-  constructor(palette: Any, create: Any, elementFactory: Any, elementRegistry: Any, flowEditorConfig: Any) {
+  constructor(
+    palette: Any,
+    create: Any,
+    elementFactory: Any,
+    elementRegistry: Any,
+    flowEditorConfig: Any,
+    modeling: Any,
+    canvas: Any,
+  ) {
     this._create = create;
     this._elementFactory = elementFactory;
     this._elementRegistry = elementRegistry;
     this._config = flowEditorConfig;
+    this._modeling = modeling;
+    this._canvas = canvas;
     palette.registerProvider(this);
   }
 
+  /** 造一枚待落的新节点(id 现取,避开已用与保留号) */
+  private _mint(spec: NewNodeSpec): Any {
+    const bo = specNode(spec);
+    bo.id = mintNodeId(spec.kind, usedIds(this._elementRegistry), this._config.reserved);
+    const size = MANUAL_SIZES[spec.kind];
+    return this._elementFactory.createShape({ width: size.w, height: size.h, businessObject: bo });
+  }
+
+  /**
+   * 点击落子的落点:视口中心起,撞车就往下让一格,直到空位。
+   *
+   * 为什么不复用拖拽那条路:`create.start` 靠鼠标**移动**取 hover 目标才算 `canExecute`,
+   * 而 click 事件到达时鼠标早已抬起 —— 拖拽在同一个调用栈里就以 `create.rejected` 收场,
+   * 一颗子也落不下(实测)。所以点击这条路直接建,不走拖拽。
+   */
+  private _freeSpot(shape: Any): { x: number; y: number } {
+    const viewbox = this._canvas.viewbox();
+    let x = snap(viewbox.x + viewbox.width / 2);
+    let y = snap(viewbox.y + Math.min(viewbox.height / 2, 200));
+    const hits = (px: number, py: number) =>
+      this._elementRegistry
+        .getAll()
+        .some(
+          (el: Any) =>
+            !el.waypoints &&
+            el.parent &&
+            !el.labelTarget &&
+            Math.abs(el.x + el.width / 2 - px) < (el.width + shape.width) / 2 + 20 &&
+            Math.abs(el.y + el.height / 2 - py) < (el.height + shape.height) / 2 + 20,
+        );
+    let guard = 0;
+    while (hits(x, y) && guard < 40) {
+      y = snap(y + 70);
+      guard += 1;
+      // 一列排满就换到右边一列重来,别无限往下掉出视野
+      if (guard % 8 === 0) {
+        x = snap(x + 160);
+        y = snap(viewbox.y + Math.min(viewbox.height / 2, 200));
+      }
+    }
+    return { x, y };
+  }
+
   getPaletteEntries(): Record<string, Any> {
     const entries: Record<string, Any> = {};
     for (const item of PALETTE_SPECS) {
-      const action = (event: Any) => {
-        const bo = specNode(item.spec);
-        bo.id = mintNodeId(item.spec.kind, usedIds(this._elementRegistry), this._config.reserved);
-        const size = MANUAL_SIZES[item.spec.kind];
-        const shape = this._elementFactory.createShape({ width: size.w, height: size.h, businessObject: bo });
-        this._create.start(event, shape);
-      };
       entries[item.key] = {
         group: "flow",
         className: item.className,
-        title: `${item.label} — 拖到画布或点击后点画布落子`,
-        action: { dragstart: action, click: action },
+        title: `${item.label} — 拖到画布,或直接点击(落在空位上,再拖到想要的地方)`,
+        action: {
+          // 拖:鼠标一路带着走,落点由手定
+          dragstart: (event: Any) => this._create.start(event, this._mint(item.spec)),
+          // 点:当场落在空位上 —— 见 `_freeSpot` 注释,点击走不通拖拽那条路
+          click: () => {
+            const shape = this._mint(item.spec);
+            this._modeling.createShape(shape, this._freeSpot(shape), this._canvas.getRootElement());
+          },
+        },
       };
     }
     return entries;