chore: import upstream snapshot with attribution

packages/plugins/fixed-drag-plugin/src/create-fixed-drag-plugin.ts

@@ -0,0 +1,50 @@
+/**
+ * Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
+ * SPDX-License-Identifier: MIT
+ */
+
+import { type Xor } from '@flowgram.ai/utils';
+import { FlowDragLayer } from '@flowgram.ai/renderer';
+import { FlowNodeEntity, FlowNodeJSON } from '@flowgram.ai/document';
+import { definePluginCreator, PluginContext } from '@flowgram.ai/core';
+
+// import { SelectorBounds } from './selector-bounds';
+
+export interface FixDragPluginOptions<CTX extends PluginContext = PluginContext> {
+  enable?: boolean;
+  /**
+   * Callback when drag drop
+   */
+  onDrop?: (ctx: CTX, dropData: { dragNodes: FlowNodeEntity[]; dropNode: FlowNodeEntity }) => void;
+  /**
+   * Check can drop
+   * @param ctx
+   * @param dropData
+   */
+  canDrop?: (
+    ctx: CTX,
+    dropData: {
+      dropNode: FlowNodeEntity;
+      isBranch?: boolean;
+    } & Xor<
+      {
+        dragNodes: FlowNodeEntity[];
+      },
+      {
+        dragJSON: FlowNodeJSON;
+      }
+    >
+  ) => boolean;
+}
+
+export const createFixedDragPlugin = definePluginCreator<FixDragPluginOptions<any>>({
+  onInit(ctx, opts): void {
+    // 默认可用，所以强制判断 false
+    if (opts.enable !== false) {
+      ctx.playground.registerLayer(FlowDragLayer, {
+        onDrop: opts.onDrop ? opts.onDrop.bind(null, ctx) : undefined,
+        canDrop: opts.canDrop ? opts.canDrop.bind(null, ctx) : undefined,
+      });
+    }
+  },
+});

packages/plugins/fixed-drag-plugin/src/hooks/use-start-drag-node.ts

@@ -0,0 +1,28 @@
+/**
+ * Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
+ * SPDX-License-Identifier: MIT
+ */
+
+import { useMemo } from 'react';
+
+import { FlowDragLayer } from '@flowgram.ai/renderer';
+import { usePlayground } from '@flowgram.ai/core';
+
+export function useStartDragNode() {
+  const playground = usePlayground();
+
+  const dragLayer = playground.getLayer(FlowDragLayer);
+
+  return useMemo(
+    () => ({
+      startDrag: dragLayer ? dragLayer.startDrag.bind(dragLayer) : (e: any) => {},
+      dragOffset: dragLayer
+        ? dragLayer.dragOffset
+        : {
+            x: 0,
+            y: 0,
+          },
+    }),
+    [dragLayer]
+  );
+}

packages/plugins/fixed-drag-plugin/src/index.ts

@@ -0,0 +1,7 @@
+/**
+ * Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
+ * SPDX-License-Identifier: MIT
+ */
+
+export * from './create-fixed-drag-plugin';
+export { useStartDragNode } from './hooks/use-start-drag-node';