chore: import upstream snapshot with attribution

packages/plugins/fixed-drag-plugin/eslint.config.js

@@ -0,0 +1,11 @@
+/**
+ * Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
+ * SPDX-License-Identifier: MIT
+ */
+
+const { defineFlatConfig } = require('@flowgram.ai/eslint-config');
+
+module.exports = defineFlatConfig({
+  preset: 'web',
+  packageRoot: __dirname,
+});

packages/plugins/fixed-drag-plugin/package.json

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+{
+  "name": "@flowgram.ai/fixed-drag-plugin",
+  "version": "0.1.8",
+  "homepage": "https://flowgram.ai/",
+  "repository": "https://github.com/bytedance/flowgram.ai",
+  "license": "MIT",
+  "exports": {
+    "types": "./dist/index.d.ts",
+    "import": "./dist/esm/index.js",
+    "require": "./dist/index.js"
+  },
+  "main": "./dist/index.js",
+  "module": "./dist/esm/index.js",
+  "types": "./dist/index.d.ts",
+  "files": [
+    "dist"
+  ],
+  "scripts": {
+    "build": "npm run build:fast -- --dts-resolve",
+    "build:fast": "tsup src/index.ts --format cjs,esm --sourcemap --legacy-output",
+    "build:watch": "npm run build:fast -- --dts-resolve",
+    "clean": "rimraf dist",
+    "test": "exit 0",
+    "test:cov": "exit 0",
+    "ts-check": "tsc --noEmit",
+    "watch": "npm run build:fast -- --dts-resolve --watch --ignore-watch dist"
+  },
+  "dependencies": {
+    "@flowgram.ai/core": "workspace:*",
+    "@flowgram.ai/utils": "workspace:*",
+    "@flowgram.ai/document": "workspace:*",
+    "@flowgram.ai/renderer": "workspace:*",
+    "inversify": "^6.0.1",
+    "reflect-metadata": "~0.2.2"
+  },
+  "devDependencies": {
+    "@flowgram.ai/eslint-config": "workspace:*",
+    "@flowgram.ai/ts-config": "workspace:*",
+    "@types/react": "^18",
+    "@types/react-dom": "^18",
+    "@vitest/coverage-v8": "^3.2.4",
+    "eslint": "^9.0.0",
+    "tsup": "^8.0.1",
+    "typescript": "^5.8.3",
+    "vitest": "^3.2.4"
+  },
+  "peerDependencies": {
+    "react": ">=16.8",
+    "react-dom": ">=16.8"
+  },
+  "publishConfig": {
+    "access": "public",
+    "registry": "https://registry.npmjs.org/"
+  }
+}

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

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+/**
+ * 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

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+/**
+ * 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

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+/**
+ * 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';

packages/plugins/fixed-drag-plugin/tsconfig.json

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+{
+  "extends": "@flowgram.ai/ts-config/tsconfig.flow.path.json",
+  "compilerOptions": {
+  },
+  "include": ["./src"],
+  "exclude": ["node_modules"]
+}

packages/plugins/fixed-drag-plugin/vitest.config.ts

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+/**
+ * Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
+ * SPDX-License-Identifier: MIT
+ */
+
+const path = require('path');
+import { defineConfig } from 'vitest/config';
+
+export default defineConfig({
+  build: {
+    commonjsOptions: {
+      transformMixedEsModules: true,
+    },
+  },
+  test: {
+    globals: true,
+    mockReset: false,
+    environment: 'jsdom',
+    setupFiles: [path.resolve(__dirname, './vitest.setup.ts')],
+    include: ['**/?(*.){test,spec}.?(c|m)[jt]s?(x)'],
+    exclude: [
+      '**/__mocks__**',
+      '**/node_modules/**',
+      '**/dist/**',
+      '**/lib/**', // lib 编译结果忽略掉
+      '**/cypress/**',
+      '**/.{idea,git,cache,output,temp}/**',
+      '**/{karma,rollup,webpack,vite,vitest,jest,ava,babel,nyc,cypress,tsup,build}.config.*',
+    ],
+  },
+});

packages/plugins/fixed-drag-plugin/vitest.setup.ts

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+/**
+ * Copyright (c) 2025 Bytedance Ltd. and/or its affiliates
+ * SPDX-License-Identifier: MIT
+ */
+
+import 'reflect-metadata';