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Step-by-Step Guide - Opera GX Extensions

This guide will walk you through the process of creating an Opera GX extension using Manifest V3.

This guide will help you create a comprehensive Opera GX extension that includes a popup interface, sidebar, options page, and service worker script. Follow these steps to build, test, and refine your extension.

Project Structure

Here’s what your project structure will look like:

my-opera-gx-extension/
│
├── manifest.json        // Manifest file defining your extension
├── popup.html           // Popup interface
├── sidebar.html         // Sidebar content
├── options.html         // Options page
├── scripts/
│   ├── popup.js         // JavaScript for the popup
│   ├── sidebar.js       // JavaScript for the sidebar
│   ├── options.js       // JavaScript for the options page
│   └── service-worker.js // Service worker script
├── styles/
│   ├── popup.css        // Styles for the popup
│   ├── sidebar.css      // Styles for the sidebar
│   ├── options.css      // Styles for the options page
├── icons/
│   ├── icon16.png       // Icon for the toolbar
│   ├── icon48.png       // Icon for extension listing
│   ├── icon128.png      // Icon for extension details

Create the Manifest File

  1. Create manifest.json in your project folder.
  2. Add the following content:
manifest.json 
{
  "manifest_version": 3,
  "name": "Advanced GX Extension",
  "version": "1.0",
  "description": "An advanced Opera GX extension with sidebar, options page, and service worker.",
  "action": {
    "default_popup": "popup.html",
    "default_icon": {
      "16": "icons/icon16.png",
      "48": "icons/icon48.png",
      "128": "icons/icon128.png"
    }
  },
  "permissions": [
    "storage",
    "tabs",
    "activeTab"
  ],
  "background": {
    "service_worker": "scripts/service-worker.js"
  },
  "sidebar_action": {
    "default_page": "sidebar.html",
    "default_icon": "icons/icon48.png",
    "default_title": "GX Sidebar"
  },
  "options_page": "options.html",
  "icons": {
    "16": "icons/icon16.png",
    "48": "icons/icon48.png",
    "128": "icons/icon128.png"
  }
}

Add a Popup Interface

  1. Create popup.html:
  2. Add styles in styles/popup.css:
  3. Add JavaScript in scripts/popup.js:
popup.html
styles/popup.css
scripts/popup.js
<!DOCTYPE html>
<html>

<head>
  <title>GX Popup</title>
  <link rel="stylesheet" href="styles/popup.css">
</head>

<body>
  <h1>Welcome to GX!</h1>
  <button id="open-sidebar">Open Sidebar</button>
  <script src="scripts/popup.js"></script>
</body>

</html>

Add a Sidebar

  1. Create sidebar.html:
  2. Add styles in styles/sidebar.css:
  3. Add JavaScript in scripts/sidebar.js:
sidebar.html
styles/sidebar.css
scripts/sidebar.js
<!DOCTYPE html>
<html>

<head>
  <title>GX Sidebar</title>
  <link rel="stylesheet" href="styles/sidebar.css">
</head>

<body>
  <h2>GX Sidebar</h2>
  <p>This is your custom sidebar.</p>
  <script src="scripts/sidebar.js"></script>
</body>

</html>

Add an Options Page

  1. Create options.html:
  2. Add styles in styles/options.css:
  3. Add JavaScript in scripts/options.js:
options.html
styles/options.css
scripts/options.js
<!DOCTYPE html>
<html>

<head>
  <title>GX Options</title>
  <link rel="stylesheet" href="styles/options.css">
</head>

<body>
  <h2>Extension Options</h2>
  <label for="theme">Choose Theme:</label>
  <select id="theme">
    <option value="light">Light</option>
    <option value="dark">Dark</option>
  </select>
  <script src="scripts/options.js"></script>
</body>

</html>

Add a Service Worker

  1. Create scripts/service-worker.js:
scripts/service-worker.js 
chrome.runtime.onInstalled.addListener(() => {
  console.log('Extension installed!');
});

chrome.runtime.onMessage.addListener((message, sender, sendResponse) => {
  if (message.action === 'ping') {
    sendResponse({ response: 'pong' });
  }
});

Test and Debug

  1. Load the Extension:
    • Go to opera://extensions.
    • Enable Developer Mode.
    • Click "Load unpacked" and select your project folder.
  2. Test Features:
    • Click the toolbar icon to test the popup.
    • Open the sidebar from the popup or extensions menu.
    • Visit opera://extensions-options to test the options page.
  3. Debug:
    • Use the developer tools (Ctrl+Shift+I) to inspect elements and view console logs.

Package and Publish

  1. Package:
    • Zip the project folder.
  2. Publish:

Congratulations! 🎉 You've created a fully functional Opera GX extension with a popup, sidebar, options page, and service worker. Explore more GX-specific APIs to enhance your extension further.

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Understanding the core concepts of browser extensions is crucial for developing effective and efficient Opera GX extensions. This guide covers the fundamental components and APIs you'll be working with.
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