Firebug 1.7: Mozilla Backend

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Mozilla back-end represents an adapter between V8 like protocol and Mozilla JSD. This adapter lives in Firebug and implements BTI interface. This adapter should replace firebug-service in Firebug 1.7.



Corresponding BTI objects:

  • BTI.BrowserFirebug firebug.js
  • BTI.CompilationUnitFirebug.SourceFile sourceFile.js
  • BTI.StackFrameFBL.StackFrame lib.js
  • BTI.BreakpointFirebug.Breakpoint breakpoint.js
  • BTI.BrowserContextFirebug.TabContext tabContext.js
  • BTI.JavaScriptContext → ?


Can you describe relations among BTI objects, which are not on the picture?

Test Cases[edit]

Exploration of some real world scenarios that happens when debugging a web application. These scenarios describe in-process usage of the firebug-service through a BTI adapter. The basic concept is as follows:

Firebug UI (Script Panel) → BTI → FBS → JSD

Where is Firebug.Debugger in this concept?

Firebug.Debugger listens for events and stores information from the events on the context object. So for example it will listen for onSourceFileCreated (or rather the BTI equivalent) and append the information about the new compilation unit on the context.


Connect to the browser.

What object in Firebug infrastructure should be responsible for this?

Get Contexts[edit]

Get list of all available contexts in the connected browser.

How TabWatcher is related to the mozilla-backend implementation?

If we think of mozilla-backend as the entire non-UI part of Firebug, then TabWatcher is part of it. TabWatcher will generate events just as it does in 1.6. Firebug.Debugger will forward some of those events through BTI.

Compilation Units[edit]

Get list of all compilation units for given context.


This scenario represents initialization of the location-list that is available on the Script panel toolbar. Displayed popup menu is initialized when the user clicks on the toolbar button.

JJB: Firebug.Debugger will get onSourceFileCreated just like 1.6. It will store info in context like 1.6. Then it will fire an event into BTI. The front end will get the event from BTI and store info in its panel. So I think we need the get-all-compilation units only for re-sync.

Get Source[edit]

Get source code (range) of given compilation unit.


This scenario happens typically when the user changes the location of the Script panel (e.g. wants to see another script file). The getSource method can be also used to get just part of the source (a range), which is used when the user scrolls the panel content. This allows to load only visible portion of the file and optimize networks traffic in case of remote debugging.

Set Breakpoint[edit]

Set a breakpoint in given compilation unit.


The Script panel is always using toggleBreakpoint call, which is consequently transformed into setBreakpoint or removeBreakpoint (depends on existence of the breakpoint).

Is the list of compilation units still stored in the BrowserContext? YES

What is the event/callback that allows to collect all compilation units? See above, it should get the compilation units as they are created.

Get Stack Trace[edit]

Get stack-trace (aka backtrace) when a breakpoint hits.


This scenario is executed when the debuggers is hanging on a breakpoint and the user shows the CallstackPanel to see the current stack-trace.

What is the JavaScriptContext here in Firebug infrastructure? I guess the JS global object

Debugger Step[edit]

Perform a debugger step (step over, step into, continue)

I don't see how to perform this action using BTI

Should this be done through an event?


Disconnect from the debugger

The same question as in the Connect case


In order to make sure the architecture is suitable also for remote debugging (the goal) there should be proper unit test written for it.

TODO: describe architecture of these tests

What mockup objects will be necessary here?