OSCON: Supercharging Firefox with Extensions
Extensions are code that run in the browser just as if it was a part of
Firefox. This talk is geared around
"the trunk" (the
upcoming Firefox 1.5). Popular examples:
- AdBlock
- Greasemonkey
- BugMeNot
- FoxyTunes
- Many toolbars: Google, Yahoo, A9, Netcraft
Structure of an Extension
- Install Manifest -- structure of extension, and where it should go in the Firefox system. Aids in deinstallation. No protection -- extensions can be written that don't cleanly uninstall.
- "Chrome" (User Interface components)
- Components (non-UI) - integrate with services, hook to other parts of system, etc.
- Defaults (Preferences)
Packaging
- "Zippy" files: zip file with a .xpi extension.
- Can package traditional "heavyweight" plugins (flash, pdf reader, etc.) as Zippy files
- Don't need GUID's anymore for directory name for extension.
- install.rdf file needs to be in root of .xpi.
UI Development with XUL
- Long topic; good resources for XUL development at developer.mozilla.org.
- Supplies UI controls, drag-n-drop, menus, toolbars, etc.
- Bound to actions through JavaScript
- You can do overlays, over Mozilla-supplied XUL, to plugin your own UI elements for the extension. XUL overlay can add, remove, or change elements in existing XUL.
- XUL is a document, which can be manipulated just like you would a DOM in DHTML.
- Site: xulplanet.com
Extension bits:
- Chrome Manifest -- where to put overlay and where to find it.
- Install Manifest
- RDF/XML file
- Identifies extension
- Compatibility extension (allows to install in Thunderbird and Firefox, for example)
- Take existing file and modify it -- to hard to do from scratch. Or grab an RDF generator.
- Update information -- for update checking
- Save as install.rdf
New testing bits:
- Can point firefox at a directory, so you don't need to repackage.
- Still need to restart browser to have it pick up new extension. But it seems like the browser will pick up code changes dynamically?
- If you turn off XUL cache, may not need to restart Firefox.
Creating New UI:
- Dialogs are in separate .xul files
- Functionality in .js files
- Use DOM methods to manipulate UI elements within XUL
- Use .css files to add images, set colors, change style, etc.
XPCOM Components
- Firefox supports XPCOM components in extensions
- This allows implementing code in JavaScript, C++ (Gecko SDK), etc. -- interacts with more of "the guts" of Firefox.
- Automatically registered by putting these files in components/ directory.
Posted by andyr at August 3, 2005 05:09 PM