The Joy of Coding

Reminder - no plan survives breakfast.

Episode guide

• Feel free to send pull requests to the repo!
• Here’s a contributing guide!
• Here’s the guide for creating pull requests that smurfd used and recommends!

Today

• Bug 1736690 - Remove or update probes expiring in Firefox 96: pictureinpicture.most_concurrent_players
  • That was easy! Patch posted.
• Questions:
  • How is gBrowser and xpcom used? Can you talk about it too?
    • gBrowser
      • gBrowser is the name of the component in a Firefox browser window that manages tabs, and the underlying infrastructure for switching tabs, adding tabs, knowing about tab switches, etc.
      • Light documentation
      • gBrowser is a window-global instance of a component called tabbrowser
      • gBrowser is a pretty bad name for what it is. Could maybe be called gTabsManager or gBrowsersManager
      • <browser>, is similar to an <iframe>
      • g is for global, a is for argument, m is for method, s is for static, k is for global constant, ALL_CAPS for global constant
      • Firefox used to not have tabs! At some point in its lineage, Firefox didn't have tabs. It was one <browser> per window. gBrowser.
        • They kept the same name when adding tabs! I think this was to make it easier to support XUL add-ons that relied on touching gBrowser. The new gBrowser variable had the same interface as the old one but would forward calls to the currently selected <browser>.
      • Source for reading
    • XPCOM
      • It's a very old Mozilla technology modeled after COM from Microsoft
      • Infrastructure for defining interfaces for components that are implementation-language agnostic
        • This means a component written in language A can in theory talk to a component written in language B by way of an interface defined in an (XP)IDL file (.idl)
      • The dream was that Mozilla-backed applications could be written in whatever language you wanted so long as it "supported XPCOM/XPConnect".
      • XPCOM components these days are written in C++, JavaScript or Rust
      • Registry of XPCOM components, and XPCOM component singletons ("services")
      • Cc (Components.classes), Ci (Components.interfaces)
      • let referrerInfo = Cc["@mozilla.org/referrer-info;1"].createInstance(Ci.nsIReferrerInfo);
      • deCOMtamination of the Mozilla source code
        • WebIDL Bindings (.webidl)
        • https://github.com/mdn/archived-content/tree/main/files/en-us/mozilla/tech/xpcom
    • Help us port documentation! From here!
      • First find the documentation that you want to port in the GitHub repository
      • File a bug blocking this bug
      • Follow these instructions to convert the document to an RST file
      • Use this example as a template
      • Post for review!
  • Can you explain the process of writing "These Weeks in Firefox" (from start to finish) ?
  • WebExtensions and how they interact with DocShells / BrowsingContexts
  • How a patch gets into Firefox, from start to finish!

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Chat

• Join us in the Livehacking room on Mozilla’s Matrix instance! Here’s documentation on how to join. I’m only sorta monitoring the Twitch chat. A bot will try to bridge Matrix and Twitch (joc-bridgebot).

Links

• Alessandro Castellani has been streaming himself livehacking on Thunderbird
• emilio hacks on Firefox!
• Compiler Compiler - watch a Mozilla engineer hack on the SpiderMonkey JavaScript engine!
• How mconley uses Mercurial
• Fission - what is it, and how does it work?
• Andreas Kling hacks on a custom browser engine for a hand-rolled OS called SerenityOS
• The Joy of Coding: Community-Run Episode guide
  • Feel free to send pull requests to the repo!
  • Here’s the guide for creating pull requests that smurfd used and recommends!
• Check out Josh Marinacci hacking on Firefox Reality, our nascent VR browser!
• I've been mirroring the episodes to YouTube
• Code Therapy with Danny O’Brien
• Watch a developer put together a Windows game from scratch (no third-part engines) - really great explanations: https://handmadehero.org/
• /r/WatchPeopleCode for more livehacking!

Glossary

• BHR - “Background Hang Reporter”, a thing that records information about when Firefox performs poorly and sends it over Telemetry
• e10s ("ee ten ESS") - short for Electrolysis, which is the multi-process Firefox project
• CPOW ("ka-POW" or sometimes "SEE-pow") = Cross-Process Object Wrapper. See this blog post.
• Deserialize - "turn a serialized object back into the complex object”
• Serialize - "turn a complex object into something that can be represented as primitives, like strings, integers, etc
• Regression - something that made behaviour worse rather than better. Regress means to “go backward”, more or less.
• l10n - localization
• a11y - accessibility
• i18n - internationalization
• k8s - kubernetes

Feedback

• @mconley@mastodon.social on Mastodon
• @mike_conley on Twitter
• mconley in IRC on irc.mozilla.org
• mikeconley.ca/blog
• mconley at mozilla dot com