[Kde-bindings] Re: Custom properties on QObjects defined in qtruby

Sven Moritz Hallberg hallberg at pre-sense.de
Wed Apr 13 18:17:10 UTC 2011

On 04/12/2011 05:34 PM, Arno Rehn wrote:
> qt_readprop should already return a Qt::Variant. In C++, you now have to 
> extract the pointer of the underlying QVariant and assign that to _o[0].

thanks, here's what i've got on the C++ side now:

    else if (_c == QMetaObject::ReadProperty) {
        VALUE variant = rb_funcall(self, rb_intern("qt_readprop"), 1, argv[1]);
        smokeruby_object *smoke_variant = value_obj_info(variant);
        _o[0] = smoke_variant->ptr;
    else if (_c == QMetaObject::WriteProperty) {
        smokeruby_object *smoke_variant = alloc_smokeruby_object(true,
                qtcore_Smoke, qtcore_Smoke->idClass("QVariant").index, _o[0]);
        VALUE variant = set_obj_info("Qt::Variant", smoke_variant);
        rb_funcall(self, rb_intern("qt_writeprop"), 2, argv[1], variant);

this looks pretty good, reading and writing the property from the ruby side
with property and setProperty makes a roundtrip through qt_metacall and
returns the correct result. however, no such luck for QML so far... that still
shows an empty string, even though it *does* go through qt_metacall and
*setting* the property from QML works! the following is trace output i'm
generating to show what's going on:

[qtruby] we're in qt_metacall!! _c=1          # ReadProperty
[ruby] qt_readprop(0 "stuff") -> "ahoj"       # ruby side fetching the value
[ruby] reading property -> "ahoj"             # result: initial value
[qtruby] we're in qt_metacall!! _c=2          # WriteProperty
[ruby] qt_writeprop(0 "stuff", "hollo!")      # ruby side setting the value
[ruby] Dings#changeStuff("hollo!")            # setter method being called
[ruby] writing property -> true               # result: success
[qtruby] we're in qt_metacall!! _c=1          # ReadProperty
[ruby] qt_readprop(0 "stuff") -> "hollo!"     # ...
[ruby] reading property -> "hollo!"           # result: changed value
[qml] dings properties:                       # enumerating properties...
[qml]   foo: [object Object]
[qtruby] we're in qt_metacall!! _c=1          # objectName (twice?)
[qtruby] we're in qt_metacall!! _c=1
[qml]   objectName:
[qml]   changeStuff: [object Object]          # slot
[qml]   stuffChanged: [object Object]         # signal
[qtruby] we're in qt_metacall!! _c=1          # ReadProperty
[ruby] qt_readprop(0 "stuff") -> "hollo!"     # ruby side: as expected
[qtruby] we're in qt_metacall!! _c=1          # twice?
[ruby] qt_readprop(0 "stuff") -> "hollo!"     # ...
[qml]   stuff:                                # empty?!

then setting and enumerating again (some lines omitted):

[qml] calling changeStuff slot                # dings.changeStuff("hey")
[qtruby] we're in qt_metacall!! _c=0          # InvokeMetaMethod
[ruby] Dings#changeStuff("hey")               # setter on ruby side
[qml] assigning property                      # dings.stuff = "ho"
[qtruby] we're in qt_metacall!! _c=2          # WriteProperty
[ruby] qt_writeprop(0 "stuff", "ho")
[ruby] Dings#changeStuff("ho")
[qml] dings properties:                       # enumerating...
[qml]   foo: [object Object]
[qml]   objectName:
[qml]   changeStuff: [object Object]
[qml]   stuffChanged: [object Object]
[ruby] qt_readprop(0 "stuff") -> "ho"         # ReadProperty called and...
[ruby] qt_readprop(0 "stuff") -> "ho"         # ...returning correct value
[qml]   stuff:                                # still, empty!?

maybe you have an idea which piece is missing... otherwise i'll do some more

> You probably have to include some checks whether the property does really
> exist

i do simple checks and have readprop/writeprop fail silently. i get nil when
reading, false from setProperty, and NoMethodError trying to assign. i guess
that's right...

> If you haven't found it already, here's the relevant C++ code from the C#
> bindings:

thanks! i hadn't.

Sven Moritz Hallberg                      hallberg at pre-sense.de
                                  Tel. +49 - 40 - 244 2407 - 28
                                  Fax  +49 - 40 - 244 2407 - 24
PRESENSE Technologies GmbH            Sachsenstr. 5, D-20097 HH
                                         USt-IdNr.: DE263765024
Geschäftsführer/Managing Directors       AG Hamburg, HRB 107844
Till Dörges           Jürgen Sander              Axel Theilmann

-------------- next part --------------
A non-text attachment was scrubbed...
Name: signature.asc
Type: application/pgp-signature
Size: 262 bytes
Desc: OpenPGP digital signature
URL: <http://mail.kde.org/pipermail/kde-bindings/attachments/20110413/aad8ccb4/attachment.sig>

More information about the Kde-bindings mailing list