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https://github.com/ganeshrvel/tutorial-electron-window-switching

Prevent duplicate window instance invoked by the main and renderer processes in an electron app
https://github.com/ganeshrvel/tutorial-electron-window-switching

electron node nodejs renderer

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Prevent duplicate window instance invoked by the main and renderer processes in an electron app

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# Prevent duplicate instances of the same window, invoked by different processes, in an electron app.

- Author: [Ganesh Rathinavel](https://www.linkedin.com/in/ganeshrvel "Ganesh Rathinavel")
- License: [MIT](https://github.com/ganeshrvel/tutorial-electron-window-switching/blob/master/LICENSE "MIT")
- Website URL: [https://github.com/ganeshrvel/tutorial-electron-window-switching](https://github.com/ganeshrvel/tutorial-electron-window-switching/ "https://github.com/ganeshrvel/tutorial-electron-window-switching")
- Repo URL: [https://github.com/ganeshrvel/tutorial-electron-window-switching](https://github.com/ganeshrvel/tutorial-electron-window-switching/ "https://github.com/ganeshrvel/tutorial-electron-window-switching")
- Contacts: ganeshrvel@outlook.com

### The challenge
In an electron app, two or more operating system level processes run concurrently — the "main" and "renderer" processes.

Because these processes are isolated from each other, child window instance, has to be loaded separately for both - main and renderer processes. This phenomenon raises another issue— duplicate windows for the same URL origin

I have spent a significant amount of time researching on preventing the issue of duplication of windows for the same URL origin. This was originally implemented inside [OpenMTP - Advanced Android File Transfer Application for macOS](https://github.com/ganeshrvel/openmtp "OpenMTP - Advanced Android File Transfer Application for macOS").

### Implementation:

Here, as an example, I will be creating a privacy policy window which can be invoked by both menu item and as well as an anchor tag.

- Install packages

```shell
$ npm install react-helmet

or

$ yarn add react-helmet
```

- Create a file *create-windows.js* and add the below code

```javascript
import { BrowserWindow, remote } from 'electron';
const PRIVACY_POLICY_PAGE_TITLE = `Privacy Policy`; // this will be used as an identifier to capture the same browser instance
let privacyPolicyWindow = null;

/**
* Privacy Policy Window
*/

const undefinedOrNull = _var => {
return typeof _var === "undefined" || _var === null;
};

const loadExistingWindow = (allWindows, title) => {
if (!undefinedOrNull(allWindows)) {
for (let i = 0; i < allWindows.length; i += 1) {
const item = allWindows[i];
if (item.getTitle().indexOf(title) !== -1) {
item.focus();
item.show();

return item;
}
}
}

return null;
};

const createWindow = isRenderedPage => {
const config = {
width: 800,
height: 600,
minWidth: 600,
minHeight: 400,
show: false,
resizable: true,
title: `${PRIVACY_POLICY_PAGE_TITLE}`,
minimizable: true,
fullscreenable: true,
webPreferences: {
nodeIntegration: true
}
};

// incoming call from a rendered page
if (isRenderedPage) {
const allWindows = remote.BrowserWindow.getAllWindows();

return loadExistingWindow(allWindows, PRIVACY_POLICY_PAGE_TITLE)
? null
: new remote.BrowserWindow(config);
}

// incoming call from the main process
const allWindows = BrowserWindow.getAllWindows();

return loadExistingWindow(allWindows, PRIVACY_POLICY_PAGE_TITLE)
? null
: new BrowserWindow(config);
};

export const privacyPolicyCreateWindow = (isRenderedPage = false) => {
try {
if (privacyPolicyWindow) {
privacyPolicyWindow.focus();
privacyPolicyWindow.show();
return privacyPolicyWindow;
}

// show the existing privacyPolicyWindow
const _privacyPolicyWindowTemp = createWindow(isRenderedPage);
if (!_privacyPolicyWindowTemp) {
return privacyPolicyWindow;
}

privacyPolicyWindow = _privacyPolicyWindowTemp;
privacyPolicyWindow.loadURL(
`file://path/to/my-app/app/index.html#privacyPolicyPage`
); // @todo: change the path accordingly

privacyPolicyWindow.webContents.on("did-finish-load", () => {
privacyPolicyWindow.show();
privacyPolicyWindow.focus();
});

privacyPolicyWindow.onerror = error => {
console.error(error, `createWindows -> privacyPolicyWindow -> onerror`);
};

privacyPolicyWindow.on("closed", () => {
privacyPolicyWindow = null;
});

return privacyPolicyWindow;
} catch (e) {
console.error(e, `createWindows -> privacyPolicyWindow`);
}
};
```

- Edit your *menu.js* file

```javascript
import { privacyPolicyWindow } from './create-windows';

// Add to your menu
submenu: [
{
label: 'Privacy Policy from main process',
click: () => {
privacyPolicyWindow(false);
}
}
]
```

- The *PrivacyPolicyPage/index.jsx*

```javascript
import React, { Component } from 'react';
import { Helmet } from 'react-helmet';

const PRIVACY_POLICY_PAGE_TITLE = `Privacy Policy`;

class PrivacyPolicyPage extends Component {
render() {
return (



{PRIVACY_POLICY_PAGE_TITLE}


Window body




);
}
}

export default PrivacyPolicyPage;
```

- Edit your router file

```javascript
import PrivacyPolicyPage from './PrivacyPolicyPage';

//Add the route

```

- Add an anchor tag inside your home page

```javascript
import { privacyPolicyWindow } from './create-windows';

{
privacyPolicyWindow(true);
}}
>
Privacy Policy from the renderer process

```

### Conclusion

- call **privacyPolicyCreateWindow(true)** from renderer process and call **privacyPolicyCreateWindow(false)** from the main process.
- *privacyPolicyCreateWindow* method will look up for the existing windows which match the title string and it returns the pre-existing window if it finds any.

### Clone
```shell
$ git clone --depth 1 --single-branch --branch master https://github.com/ganeshrvel/tutorial-electron-window-switching.git

$ cd tutorial-electron-window-switching
```

### Contribute
- Fork the repo and create your branch from master.
- Ensure that the changes pass linting.
- Update the documentation if needed.
- Make sure your code lints.
- Issue a pull request!

When you submit code changes, your submissions are understood to be under the same [MIT License](https://github.com/ganeshrvel/tutorial-electron-window-switching/blob/master/LICENSE "MIT License") that covers the project. Feel free to contact the maintainers if that's a concern.

### Buy me a coffee
Help me keep the app FREE and open for all.
Paypal me: [paypal.me/ganeshrvel](https://paypal.me/ganeshrvel "paypal.me/ganeshrvel")

### Contacts
Please feel free to contact me at ganeshrvel@outlook.com

### More repos
- [OpenMTP - Advanced Android File Transfer Application for macOS](https://github.com/ganeshrvel/openmtp "OpenMTP - Advanced Android File Transfer Application for macOS")
- [Tutorial Series by Ganesh Rathinavel](https://github.com/ganeshrvel/tutorial-series-ganesh-rathinavel "Tutorial Series by Ganesh Rathinavel")
- [npm: electron-root-path](https://github.com/ganeshrvel/npm-electron-root-path "Get the root path of an Electron Application")
- [Electron React Redux Advanced Boilerplate](https://github.com/ganeshrvel/electron-react-redux-advanced-boilerplate "Electron React Redux Advanced Boilerplate")

### License
tutorial-electron-window-switching is released under [MIT License](https://github.com/ganeshrvel/tutorial-electron-window-switching/blob/master/LICENSE "MIT License").

Copyright © 2018-Present Ganesh Rathinavel