I think noteId could be undefined? If there's no note in the notebook for example

`NoteTextViewer` was converted to a function component to allow getting the window ID with the `useContext(WindowIdContext)` hook. The window ID is used to ensure that when plugins call `response = await webviewApi.postMessage(...)`, the response is sent to the correct window.

This allows the main window to be closed without quitting the app, even if "show tray icon" is disabled.

The note editor and note viewer can now be open in multiple windows at the same time. To allow this, the `PostMessageService` has been updated to associate a `windowId` with plugin messages. For example, if a note viewer content script in window A calls `webviewApi.postMessage`, the `windowId` is used to send the plugin's response to window A (and not some other window with a note viewer).

`useFormNote` was updated to allow changes from one window to update other windows viewing the same note. In particular, it now uses the `ItemChange` event to detect note changes. Previously, it refreshed the note on sync start/end, decryption, or external editor note updates. Unnecessary note refreshes can cause the cursor to jump and undo history to be lost. To avoid such refreshes, - When notes are saved from an editor, a `changeId` is passed to `Note.save`. - Each editor has a unique `changeId`. - This `changeId` is included with `ItemChange` events. - The `changeId` is used to avoid refreshing when a change event was triggered by the current editor. For example, if a note is changed in editor A and also open in editor B, 1. `Note.save` is called with `changeId: 'editorChange-editor-1'`. 2. This causes an `ItemChange` event to be dispatched. 3. Editor A receives this `ItemChange` event, but ignores it because its `changeId` is `editorChange-editor-1`. 4. Editor B receives this event and **does not ignore it** because its changeId is **not** `editorChange-editor-2`.

This callback is used to update secondary windows' titlebars.

**Note**: `Navigator` was converted to a function component to allow the use of `useContext` (used to determine the current window ID).

```suggestion export const loadScript = async (script: Script, targetDocument: Document) => { ``` I'm not sure whether it's better to shadow the global `document` variable or use a different name. Tradeoffs: - **Benefit**: Shadowing the global `document` prevents the function's code from accidentally using the wrong `document` object. - **Drawback**: Shadowing `document` may make it less clear that code in the function is not necessarily referencing the global `document`.

`NoteEditor.tsx` is a new file. The old `NoteEditor.tsx` was renamed to `NoteEditorContent.tsx`. - [x] To-do: Use a different name for the note editor wrapper so that it's marked as a rename by `git`?

This code uses `CacheProvider` from `@emotion/react` to cause `react-select` to insert its styles into the new window (see [comment](https://github.com/JedWatson/react-select/issues/3680#issuecomment-809518245)). `@emotion/react` is a dependency of `react-select` and, at present, is not a direct dependency of Joplin. Adding `@emotion/react` to `app-desktop/package.json` could be problematic if `react-select` is updated without also updating the `@emotion/react` version — having multiple versions of `@emotion/react` [may cause styling issues](https://github.com/emotion-js/emotion/issues/2383) (or perhaps break styling just in new windows). See [this unmerged upstream pull request](https://github.com/JedWatson/react-select/pull/5939) for a possible future solution that doesn't involve `import`ing transitive dependencies.

Related documentation/explanation: - [React Portals](https://react.dev/reference/react-dom/createPortal#rendering-react-components-into-non-react-dom-nodes) documentation. - [StackOverflow thread](https://stackoverflow.com/questions/68464980/render-a-react-component-in-a-new-window) with discussion on how to render React components to a new window. - [A blog post](https://david-gilbertson.medium.com/using-a-react-16-portal-to-do-something-cool-2a2d627b0202) about using `createPortal` with new windows.