fix: handle Unicode characters in clipboard copy/paste and add Paste menu option (#7103)

## Summary
Use TextEncoder/TextDecoder for UTF-8 safe base64 encoding/decoding

When copying nodes containing non-Latin1 characters (e.g., Chinese
characters in localized_name field), btoa() throws an error:

InvalidCharacterError: Failed to execute 'btoa' on 'Window': The string
to be encoded contains characters outside of the Latin1 range.

The copy operation saved data to localStorage successfully, but failed
to write to the browser clipboard. On paste, the browser clipboard still
contained old data, causing the wrong node to be pasted.

<!-- Fixes #ISSUE_NUMBER -->
https://github.com/Comfy-Org/ComfyUI_frontend/issues/6993
https://github.com/Comfy-Org/ComfyUI_frontend/issues/5449
https://github.com/comfyanonymous/ComfyUI/issues/8481

## Screenshots (if applicable)
before

https://github.com/user-attachments/assets/8abd9049-91bb-4200-8853-e26753376007

after

https://github.com/user-attachments/assets/7d969f32-bb0f-4c7a-baa2-65d576a4eba2

┆Issue is synchronized with this [Notion
page](https://www.notion.so/PR-7103-fix-handle-Unicode-characters-in-clipboard-copy-paste-and-add-Paste-menu-option-2bd6d73d365081f39c40e7e7f832b97c)
by [Unito](https://www.unito.io)

---------

Co-authored-by: github-actions <github-actions@github.com>

src/composables/useCopy.ts

@@ -23,10 +23,16 @@ export const useCopy = () => {
     const canvas = canvasStore.canvas
     if (canvas?.selectedItems) {
       const serializedData = canvas.copyToClipboard()
+      // Use TextEncoder to handle Unicode characters properly
+      const base64Data = btoa(
+        String.fromCharCode(
+          ...Array.from(new TextEncoder().encode(serializedData))
+        )
+      )
       // clearData doesn't remove images from clipboard
       e.clipboardData?.setData(
         'text/html',
-        clipboardHTMLWrapper.join(btoa(serializedData))
+        clipboardHTMLWrapper.join(base64Data)
       )
       e.preventDefault()
       e.stopImmediatePropagation()

src/composables/usePaste.ts

@@ -14,9 +14,11 @@ function pasteClipboardItems(data: DataTransfer): boolean {
   const match = rawData.match(/data-metadata="([A-Za-z0-9+/=]+)"/)?.[1]
   if (!match) return false
   try {
-    useCanvasStore()
-      .getCanvas()
-      ._deserializeItems(JSON.parse(atob(match)), {})
+    // Decode UTF-8 safe base64
+    const binaryString = atob(match)
+    const bytes = Uint8Array.from(binaryString, (c) => c.charCodeAt(0))
+    const decodedData = new TextDecoder().decode(bytes)
+    useCanvasStore().getCanvas()._deserializeItems(JSON.parse(decodedData), {})
     return true
   } catch (err) {
     console.error(err)

src/lib/litegraph/src/LGraphCanvas.ts

@@ -8031,7 +8031,13 @@ export class LGraphCanvas
           has_submenu: true,
           callback: LGraphCanvas.onMenuAdd
         },
-        { content: 'Add Group', callback: LGraphCanvas.onGroupAdd }
+        { content: 'Add Group', callback: LGraphCanvas.onGroupAdd },
+        {
+          content: 'Paste',
+          callback: () => {
+            this.pasteFromClipboard()
+          }
+        }
         // { content: "Arrange", callback: that.graph.arrange },
         // {content:"Collapse All", callback: LGraphCanvas.onMenuCollapseAll }
       ]

tests-ui/tests/composables/clipboard.test.ts

@@ -0,0 +1,105 @@
+import { describe, expect, it } from 'vitest'
+
+/**
+ * Encodes a UTF-8 string to base64 (same logic as useCopy.ts)
+ */
+function encodeClipboardData(data: string): string {
+  return btoa(
+    String.fromCharCode(...Array.from(new TextEncoder().encode(data)))
+  )
+}
+
+/**
+ * Decodes base64 to UTF-8 string (same logic as usePaste.ts)
+ */
+function decodeClipboardData(base64: string): string {
+  const binaryString = atob(base64)
+  const bytes = Uint8Array.from(binaryString, (c) => c.charCodeAt(0))
+  return new TextDecoder().decode(bytes)
+}
+
+describe('Clipboard UTF-8 base64 encoding/decoding', () => {
+  it('should handle ASCII-only strings', () => {
+    const original = '{"nodes":[{"id":1,"type":"LoadImage"}]}'
+    const encoded = encodeClipboardData(original)
+    const decoded = decodeClipboardData(encoded)
+    expect(decoded).toBe(original)
+  })
+
+  it('should handle Chinese characters in localized_name', () => {
+    const original =
+      '{"nodes":[{"id":1,"type":"LoadImage","localized_name":"图像"}]}'
+    const encoded = encodeClipboardData(original)
+    const decoded = decodeClipboardData(encoded)
+    expect(decoded).toBe(original)
+  })
+
+  it('should handle Japanese characters', () => {
+    const original = '{"localized_name":"画像を読み込む"}'
+    const encoded = encodeClipboardData(original)
+    const decoded = decodeClipboardData(encoded)
+    expect(decoded).toBe(original)
+  })
+
+  it('should handle Korean characters', () => {
+    const original = '{"localized_name":"이미지 불러오기"}'
+    const encoded = encodeClipboardData(original)
+    const decoded = decodeClipboardData(encoded)
+    expect(decoded).toBe(original)
+  })
+
+  it('should handle mixed ASCII and Unicode characters', () => {
+    const original =
+      '{"nodes":[{"id":1,"type":"LoadImage","localized_name":"加载图像","label":"Load Image 图片"}]}'
+    const encoded = encodeClipboardData(original)
+    const decoded = decodeClipboardData(encoded)
+    expect(decoded).toBe(original)
+  })
+
+  it('should handle emoji characters', () => {
+    const original = '{"title":"Test Node 🎨🖼️"}'
+    const encoded = encodeClipboardData(original)
+    const decoded = decodeClipboardData(encoded)
+    expect(decoded).toBe(original)
+  })
+
+  it('should handle empty string', () => {
+    const original = ''
+    const encoded = encodeClipboardData(original)
+    const decoded = decodeClipboardData(encoded)
+    expect(decoded).toBe(original)
+  })
+
+  it('should handle complex node data with multiple Unicode fields', () => {
+    const original = JSON.stringify({
+      nodes: [
+        {
+          id: 1,
+          type: 'LoadImage',
+          localized_name: '图像',
+          inputs: [{ localized_name: '图片', name: 'image' }],
+          outputs: [{ localized_name: '输出', name: 'output' }]
+        }
+      ],
+      groups: [{ title: '预处理组 🔧' }],
+      links: []
+    })
+    const encoded = encodeClipboardData(original)
+    const decoded = decodeClipboardData(encoded)
+    expect(decoded).toBe(original)
+    expect(JSON.parse(decoded)).toEqual(JSON.parse(original))
+  })
+
+  it('should produce valid base64 output', () => {
+    const original = '{"localized_name":"中文测试"}'
+    const encoded = encodeClipboardData(original)
+    // Base64 should only contain valid characters
+    expect(encoded).toMatch(/^[A-Za-z0-9+/=]+$/)
+  })
+
+  it('should fail with plain btoa for non-Latin1 characters', () => {
+    const original = '{"localized_name":"图像"}'
+    // This demonstrates why we need TextEncoder - plain btoa fails
+    expect(() => btoa(original)).toThrow()
+  })
+})