Compatibility/System Addon/Initial Planning
- Opera Presto: http://www.opera.com/docs/browserjs/
- Opera Blink: https://github.com/operasoftware/browserjs/blob/master/OPRdesktop/browserjs-28.0.js (a less powerful version of browser.js)
- Vivaldi is said to have something similar (citation needed)
Current solutions to use cases
- Firefox for Android has a dynamic User Agent string override mechanism (see ua-update.json: https://dxr.mozilla.org/mozilla-central/source/mobile/android/app/ua-update.json.in).
Pros: simple; out of band CDN updates
Cons: only on Fennec, applies to all requests for a given domain, i.e., no conditional spoofing. simple regex tweaks only.
- Modifying User Agent with UserAgentOverrides.jsm and SiteSpecificUserAgent.js: https://bugzilla.mozilla.org/show_bug.cgi?id=1127448
Cons: has to ride trains. might require a dot release depending on the site and severity.
- Hard coding User Agent hacks in Navigator.cpp: https://bugzilla.mozilla.org/show_bug.cgi?id=1233970#c11
Pros: Get’s the job done.
Cons: Has to ride trains; Might require a dot release depending on the site and severity.
- Ability for developers to see that a site patch is enabled, with short explanation and link to bug (likely via developer console).
- Ability to temporarily disable site patch for developers to test fixes.
- Ability to modify page CSS
- Ability to mutate page DOM
- Ability to modify script (inline, external) source before execution
- Ability to hook into page load lifecycle events (script execution, CSS parsing, event handlers, etc). See http://www.opera.com/docs/userjs/specs/#evlistener
- Ability for a site patch to target a specific URI rather than entire origin.
- Ability to define setters and getters for page variables and methods (question for Hallvord: scope?)
- Injected JS should not have chrome privileges
- Injected JS should have full access to page
- Site patches should not run if modified by user.
- Possibly access/modify HTTP headers? (Unclear how useful this is, Karl is supposed to suggest a use case here.)