Cross thread issue in Qt4.8 - qt

Question

I have this code:
class CMyWindow:
class CMyWindow: public QMainWindow
{ // Q_OBJECT .... here
private:
CMyServer *server;
public:
CMyWindow(QWidget *parent): QMainWindow(parent)
{
// Setup GUI here
server = new CMyServer(this);
server->startServer();
}
void thisChangeLabelCaption(QString str) {
ui.lblStatus.setText(str);
}
}
And class CMyServer:
class CMyServer: public QTcpServer
{
protected:
void incomingConnection(int sockDesc) {
/* Why below line can't be done :-| */
((CMyWindow *) parent())->thisChangeLabelCaption("New connection");
}
}
But the line in incomingConnection() rountine seem not executed.
Please tell me solution for this problem.
Update:
As #vtmarvin said, i tried this way:
class CMyWindow: public QMainWindow
{
private:
CMyServer *server;
protected slots:
void editLabel(QString str) {
thisChangeLabelCaption(str);
}
public:
CMyWindow(QWidget *parent): QMainWindow(parent) {
server = new CMyServer(this);
server->startServer();
}
void thisChangeLabelCaption(QString str) {
ui.lblStatus.setText(str);
}
}
class CMyServer: public QTcpServer
{
Q_SIGNAL:
void setText(QString str);
protected:
void incomingConnection(int sockDesc) {
/* Why below line can't be done :-| */
emit setText("New connection");
}
public:
CMyServer(QObject *parent): QTcpServer(parent)
{
connect(this, SIGNAL(setText(QString)), parent, SLOT(editLabel(QString)), Qt::QueuedConnection);
}
}
But no better result :-(

Answer 1

You cannot change UI from other threads than the main one - the one that owns QMainWindow. I suppose your CMyServer::incomingConnection is invoked by the QTcpServer thread. You must do a signal-slot with Qt::QueuedConnection type.