Problems with setCentralWidget

[Rockem]

Hello all,

I have this code

class QTWindowView : public WindowView, public QTextEdit{
public:
	QString getText() const;
	void setText(const QString & text);
};

class QTWindowView : public WindowView, public QTextEdit{
public:
	QString getText() const;
	void setText(const QString & text);
};

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and when I try to setCentralWidget with this class on QMainWindow
I get a segmentation fault.
whats more, on Windows the code DOES work, but on linux
it crash

any suggestions ?
Eli

[jpn]

Hard to say with given code, but at least QTextEdit should be the first in the inheritance list if you ever plan to add any Qt meta system stuff to your class. Could you paste backtrace from gdb by the time of crash?

[Rockem]

this is the backtrace:
Program received signal SIGSEGV, Segmentation fault.
[Switching to Thread -1225295584 (LWP 4130)]
0xb77e5b11 in QWidget::isAncestorOf (this=0x8097140, child=0x804ca08) at kernel/qwidget.cpp:6049
/home/elis/downloads/qt-x11-opensource-src-4.3.4/src/gui/kernel/qwidget.cpp:6049:181840:beg:0xb77e5b11


Eli

[wysota]

This is not a backtrace. Use the "bt" command in gdb.

[Rockem]

ok, thanx ..

#0 0xb77e5b11 in QWidget::isAncestorOf (this=0x8097140, child=0x804ca08) at kernel/qwidget.cpp:6049
#1 0xb77f3b02 in QWidget::setParent (this=0x8097140, parent=0x80ce47c, f=@0xbf83af20) at kernel/qwidget.cpp:7643
#2 0xb77f3f38 in QWidget::setParent (this=0x804ca08, parent=0x8097140) at kernel/qwidget.cpp:7616
#3 0xb77cfb91 in QLayout::addChildWidget (this=0x80e85a8, w=0x8097140) at kernel/qlayout.cpp:931
#4 0xb7af92f9 in QMainWindowLayout::setCentralWidget (this=0x80e85a8, widget=0x8097140) at widgets/qmainwindowlayout.cpp:1789
#5 0xb7af7080 in QMainWindow::setCentralWidget (this=0x80ce47c, widget=0x8097140) at widgets/qmainwindow.cpp:554
#6 0x0804e01b in QTMainWindowView::setCenterWidget (this=0x80ce478, view=0x8097140) at src/qt/qtmainwindowview.cpp:10
#7 0x0804d01c in MainWindow (this=0xbf83b0b0) at src/mainwindow.cpp:17
#8 0x0804e23c in runApp (app=@0xbf83b100, argc=1, argv=0xbf83b1b4) at tests/tests.cpp:34
#9 0x0804e783 in main (argc=1, argv=0xbf83b1b4) at tests/tests.cpp:49

[wysota]

What is runApp() and QTMainWindowView?

[Rockem]

runApp:

int runApp(QApplication& app, int argc, char** argv) {
	MainWindow::setViewFactory(new QTViewFactory);
	MainWindow mainWin;
	if(mainWin.evaluateArguments(argc, argv)) {
		mainWin.show();
		return app.exec();
	}
	return -1;
}

int runApp(QApplication& app, int argc, char** argv) {
	MainWindow::setViewFactory(new QTViewFactory);
	MainWindow mainWin;
	if(mainWin.evaluateArguments(argc, argv)) {
		mainWin.show();
		return app.exec();
	}
	return -1;
}

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QTWindowView:

class QTMainWindowView : public MainWindowView, public QMainWindow {
public:
	void show();
	void setCenterWidget(WidgetView* view);
};

class QTMainWindowView : public MainWindowView, public QMainWindow {
public:
	void show();
	void setCenterWidget(WidgetView* view);
};

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[wysota]

1. QWidget::show() is not virtual,
2. What's the contents of QTMainWindowView::setCenterWidget ?
3. What is MainWindowView?
4. I think you are lacking the Q_OBJECT macro somewhere, isAncestorOf() may be needing it, but it's hard to say that without seeing the whole code.

[Rockem]

[QUOTE]1. QWidget::show() is not virtual [QUOTE]
I know

2. What's the contents of QTMainWindowView::setCenterWidget ?

void QTMainWindowView::show() {
	QMainWindow::show();
}
 
void QTMainWindowView::setCenterWidget(WidgetView* view) {
	QMainWindow::setCentralWidget((QWidget*)view);
}

void QTMainWindowView::show() {
	QMainWindow::show();
}

void QTMainWindowView::setCenterWidget(WidgetView* view) {
	QMainWindow::setCentralWidget((QWidget*)view);
}

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WidgetView is my parent view for all the view classes (it's empty)

3. What is MainWindowView?

it is pure abstract class that defines the show and setCentralWidget

4. I think you are lacking the Q_OBJECT macro somewhere, isAncestorOf() may be needing it, but it's hard to say that without seeing the whole code.

ummmm .... ?

[wysota]

1. QWidget::show() is not virtual

I know

Good, so why do you reimplement it anyway?

void QTMainWindowView::show() {
	QMainWindow::show();
}
 
void QTMainWindowView::setCenterWidget(WidgetView* view) {
	QMainWindow::setCentralWidget((QWidget*)view);
}

void QTMainWindowView::show() {
	QMainWindow::show();
}

void QTMainWindowView::setCenterWidget(WidgetView* view) {
	QMainWindow::setCentralWidget((QWidget*)view);
}

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WidgetView is my parent view for all the view classes (it's empty)

Why do you cast to QWidget* in line 6? If your compiler complains without that cast then that's probably your problem - your widget is not a widget...

ummmm .... ?

Yeah... "ummmm" is right... Start by changing the inheritance order as already suggested, remove the cast to QWidget and tell us why you need the additional two layers over QWidget...

[Rockem]

I'm using a Abstract Factory (Pattern)
which means that I'm accessing all my views (=qt widgets) through
interfaces (=abstract classes)
that is why I need the to reimplement show()

this is also why I have two more layers

I also need the cast coz WidgetView is NOT QWidget.