#include <QApplication>
#include <QDialog>
#include <QBoxLayout>
#include <QLineEdit>
#include <QPushButton>

class SomeDialog : public QDialog
{
public:
	SomeDialog( QWidget* parent = Q_NULLPTR ) : QDialog( parent )
	{
		QBoxLayout* l = new QVBoxLayout( this );
		l->addWidget( new QLineEdit( this ) );
		QPushButton* btn = new QPushButton( "exec", this );
		l->addWidget( btn );
		connect( btn, &QPushButton::clicked, this, [this]() { 
			SomeDialog* d = new SomeDialog( this );
			d->exec(); } );
	}
};

int main(int argc, char *argv[])
{
	qputenv( "QT_IM_MODULE", QByteArray( "qtvirtualkeyboard" ) );

	QApplication a( argc, argv );
	SomeDialog w;
	w.show();
	return a.exec();
}