[Kde-bindings] Qyoto: SIGNALS/SLOTS

Richard Dale Richard_Dale at tipitina.demon.co.uk
Thu Dec 8 20:58:38 UTC 2005

On Thursday 08 December 2005 19:32, Arno Rehn wrote:
> Am Mittwoch, 7. Dezember 2005 17:43 schrieb Richard Dale:
> > On Wednesday 07 December 2005 15:36, Arno Rehn wrote:
> > > Hi,
> > >
> > > I experimented a bit and created a more complex Hello-World sample app.
> > > I wanted to connect the "clicked()" signal of a button to the "quit()"
> > > slot of QApplication. Got a SIGSEGV.
> > > I looked into the Qt.cpp of qtruby and it seems as signals and slots
> > > are a bit difficult.
> >
> > QtRuby dynamically constructs QMetaObjects, rather than it being done at
> > compile time by the moc pre-processor. But the actual runtime is
> > identical. We need a way of denoting which methods are slots in C#, and I
> > assume we can use 'attributes' (or are they called 'annotations' I've
> > forgotten). Maybe you could have a look at how we might mark slots, and
> > then the runtime side should be very similar to QtRuby. We don't have to
> > invent anything much new apart from that.
> OK, I found out how to mark Signals/Slots with Attributes. I attached an
> example.
That looks good. In Qt4 there is a macro 'Q_SLOTS' to use instead of the 
'slots' moc keyword because of a clash with the Boost library. So maybe slots 
could be marked like this, to look more like that macro:

	public void mySlot()

Maybe signals need to map onto delegates, rather than ordinary methods.

At the moment an interface is generated containing the type signatures of 
signals like this:

	public interface IQApplicationSignals {
		void LastWindowClosed();
		void AboutToQuit();
		void GuiThreadAwake();

And I was thinking of having a QObject.Emit() method which returned a 
transparent proxy, so you could invoke a signal with like this:

(LastWindowClosed) myInstance.Emit()

And it would be forwarded to SignalInvocation.Invoke(), in a similar manner to 
how ordinary method calls get diverted to SmokeInvocation.Invoke() at the 

But slots are easiest to get working first though, and marking them with 
attributes like you've done looks pretty good to me.

-- Richard

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