GammaRay - Introspection/Debugging Tool for Qt Applications

Milian Wolff mail at
Mon Oct 31 22:22:07 GMT 2011

On Monday 31 October 2011 22:36:08 Peter =?ISO-8859-1?Q?K=FCmmel?= wrote:
> On 30.10.2011 13:21, Volker Krause wrote:
> > Hi!
> > 
> > During the Qt Dev Days in Munich last week we (KDAB) released a new Free
> > Software introspection/debugging tool for Qt applications, called
> > GammaRay:
> >
> > 
> > It hooks itself into a Qt application (at start-up or at runtime) using a
> > variety of methods (ranging from assembler hacks to (ab)using Qt plug-ins)
> > and uses the Qt meta object system for introspecting object, properties,
> > signals, slots, signal/slot connections, etc. Nothing really new until
> > here, tools like Qt Inspector or KSpy can do this already. On top of that
> > GammaRay adds a bunch of higher level tools though, for example:
> > 
> > - QWidget layout overlay, similar to designer
> > - Inspecting a QGraphicsScene and various details of QGraphicsItems
> > (visualizing shapes, bounding rects, transformation origins, etc)
> > - Looking at the full (proxy) model hierarchy and all intermediate results
> > in there
> > - a live updating QStateMachine visualization
> > - attaching of QScriptEngineDebugger and QWebInspector to the
> > corresponding
> > objects in the application
> > - a QTextDocument document object model viewer
> > 
> > Additionally, GammaRay has a plug-in interface for adding new tools, say a
> > KJob tracker.
> > 
> > GammaRay works on Linux, Mac and Windows (MSVC only so far), it needs to
> > be
> > compiled against the same Qt version used by the application you are about
> > to debug though. There's also a Qt Creator plug-in for it
> > (
> > 
> > Some screenshots can be found here:
> > 
> > GammaRay was originally developed in support for the Kontact Touch
> > project,
> > back when there wasn't a QML debugger yet. The proxy model debugger also
> > proved quite helpful on KMail, maybe it can help some of you as well :)
> > 
> > Needless to say that contributions are very much welcome.
> > 
> > regards
> > Volker
> Congratulation for this very nice tool!
> I've also tried to attach to console apps without success.
> Then I realized that you use the hijacked process to show
> the GammaRay mainwindow which is not possible in a
> QCoreApplication executable.

True, this won't work...

> So I wonder how difficult it would be to run GammaRay in a
> different process? Then an IPC mechanism is needed for all
> the information. Would this be fast enough? Do you plan
> to add this in future?

We thought about it but at least DBUS will be too slow I'd say. Furthermore I 
doubt it's easy or even possible to get all the features of gammaray working 

> Is there a single point where all the information of
> the target process goes through or is it all over the place?
> I assume at least each plugin pulls information by itself.

See probe.cpp - that is the "core". The plugins essentially just use data from 
one of the models, e.g. ObjectTreeModel, ObjectListModel and ConnectionModel.

> And how much does the current code depend on x86/64?
> Would it be hard to support PPC?

At least the GDB and Style injectors should be portable already. The others, 
esp. WinDLL , are probably architecture specific.

The preload code for Mac does not seem to be architecture specific though - at 
least to my quick glance. Have you tried it out with PPC? Maybe it works 
already. At least the style/gdb injectors as I said above should work.

Milian Wolff
mail at
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