problem: qthread emitting a signal with any object type

hi.

i'm using qt 4.2.x on visual studio + winxp and maybe it sound silly, but the following problem irritates me a little bit:

there is a qthread class, which tires to get new images from a device. the device has a "grab timeout". if a timeout occurs, an exception is thrown. if a new image could be grabbed, a signal should be emitted, transfering the new image to the calling (main/parent) thread for processing/displaying or what ever.

i tried like this...

the threads run method:

Code:

---

void getimg_thread::run()
{
	while(!quitthread)
	{
		try
		{
			grab_image(&img);
			emit newimg(img);
			msleep(1);
		}
		catch(AException &ex)
		{
		}
	}
}

---

the defined signal:

Code:

---

signals:
	void newimg(imageobject);

---

the slot to receive and process the emitted signal:

Code:

---

private slots:
	void newimage_received(imageobject nimg);

---

and finally the connect part:

Code:

---

connect(grabimg, SIGNAL(newimg(imageobject)), this, SLOT(newimage_received(imageobject)));

---

but my headache starts here: the connect does not work somehow, my slot is never called. i tried many things, but without any luck.

it somehow just worked as i emitted an "int". then my slot was called properly. i also tried to emit a signal with a QList<int>, which is also working, e.g.:

Code:

---

...
signals:
	void newimg(const QList<int>*);
...
	QList<int> *a = new QList<int>;
	a->append(1);
	emit newimg(a);
...
private slots:
	void newimage_received(QList<int> *nimg);
...
	connect(grabimg, SIGNAL(newimg(QList<int> *)), this, SLOT(newimage_received(QList<int> *)));
...

---

but if i'm using my imageobject class (which is not a qt object), it won't work:

Code:

---

...
signals:
	void newimg(QList<imageobject>*);
...
	QList<imageobject> *a = new QList<imageobject>;
	a->append(img);
	emit newimg(a);
...
private slots:
	void newimage_received(QList<imageobject> *nimg);
...
	connect(grabimg, SIGNAL(newimg(QList<imageobject>*)), this, SLOT(newimage_received(QList<imageObject>*)));
...

---

i'm confused. why is QList<int> working and QList<imageobject> not? i mean, an emitted signal is able to transfer any object i define or not!? any ideas? help :|

regards,

criss

Custom types (imageobject) must be made known to the meta object system of Qt. See Q_DECLARE_METATYPE() and qRegisterMetaType().

It's worth looking at the debugging console sometimes ;) Try running your application with console enabled and see what info you get. And then read this:
http://doc.trolltech.com/4.2/qmetaty...gisterMetaType

Argh... J-P beat me to it :)

thanks a lot guys, i'm proud to know a place like this forum (which is the best among the others)...

greetings from istanbul :D

krzysztof