Serenade Chrome Extension

Source for the Serenade Chrome Extension

Installation

1. Download build.zip and unzip
2. In Chrome, go to chrome://extensions and enable Developer Mode
3. Click "Load unpacked" and select the unzipped build folder

You may need to reload any tabs that were open before the extension was loaded.

Design

Chrome extensions generally contain three types of scripts that each have access to different parts of the browser API and page content:

• Background workers/extension code have full access to the browser APIs and handles the parts of the extension that do not depend on the content of a given page.
• Content scripts have access to some of the browser APIs and access to the page DOM, but do not have access to any of the window properties or the page's global namespace.
• Injected content scripts are embedded script tags that are added by the content script, and have full access to the page content as well as the window properties and the page's global namespace.

Each of these script types can communicate between each other with browser events. The source for this extension falls into these categories as follows:

• Extension code
  • extension.ts: Entry-point for the extension
  • ipc.ts: Handles communication between the Serenade app and the Chrome extension. Also determines which command handler to send each incoming command to.
  • extension-command-handler.ts: Handles commands that do not need page content/require access to the browser APIs (e.g. tab management)
• Content scripts
  • content-script.ts: Adds the tag containing the injected scripts and sets up communication between ipc.ts and the injected code
• Injected scripts
  • injected.ts: Sets up injected code and handles communication between injected code and the content script
  • injected-command-handler.ts: Handles commands that need access to the page content or objects in the page's global namespace
  • editors.ts: Defines interactions with text editors using a common API

Most of the extensions functionality is in three files: extension-command-handler.ts, injected-command-handler.ts, and editors.ts.

Command Handlers

Both command handlers contain functions named for the various command types in the Serenade Protocol. These functions take a data object as a parameter and return a promise to the relevant response data (if any).

Editors

We currently support editing text in textarea and input tags, as well as a few third-party browser editors (Ace, CodeMirror, and Monaco). Each of these editor types are extensions of the Editor class that implement these functions:

• active(): Returns whether the current active DOM element is of the object type
• getEditorState(): Returns an object containing the source, cursor offset, file name, and a boolean to indicate the source was available
• setSelection(cursor: number, cursorEnd: number): Sets the selection to be between cursor and cursorEnd
• setSourceAndCursor(source: string, cursor: number): Sets the content of the editor to source and moves the cursor to cursor
• undo/redo: Undo/redo edits

Supporting a new editor is a matter of implementing these functions.

The Editor class also contains some helper functions to determine a suitable file name from a language name and to calculate a cursor position from the cursor row and column and vice versa. Third-party editors also have a private editor() method to capture the Javascript object corresponding to the editor from the page's global namespace, making the third-party API available.

Development

1. Clone this repository
2. Run npm install to get dependencies
3. Run npm run build (or npm run watch to automatically update while iterating)

• This creates build/extension.js, build/content-script.js, and build/injected.js

4. In Chrome, go to chrome://extensions and enable Developer Mode
5. Click "Load unpacked" and select the chrome repository
6. Test the extension
   • When iterating, make sure you update the extension by clicking "Update" on the Chrome Extensions page and refreshing the page you are using to test
   • Running npm run test will serve a simple page at localhost:8001 with instances of the various inputs/code editors we support
   • The source for this test page can be found in src/test

Deployment

1. Update the version number in manifest.json
2. Run npm run dist
3. Upload the new build.zip file to the Chrome Web Store