I worked on a drawing software in 2012-13, but haven't touched it since. Now I'm brushing it up, and it works fine, except a costum dialog that doesn't work anymore.
Many things can have changed, but my search has so far been without result.
Here's the header and cpp-file:

penChooser.h

Qt Code: 
  1. #ifndef PENCHOOSER_H
  2. #define PENCHOOSER_H
  3.  
  4. #include <QColorDialog>
  5. #include <QLabel>
  6. #include <QPushButton>
  7. #include <QSpinBox>
  8. #include <QComboBox>
  9. #include <QVBoxLayout>
  10. #include <QGridLayout>
  11.  
  12. class penChooser : public QDialog
  13. {
  14.     Q_OBJECT
  15. public:
  16.     explicit penChooser(QDialog *parent = nullptr);
  17.  
  18.     QColorDialog *colordialog;
  19.     QLabel *labWidth;
  20.     QSpinBox *sbWidth;
  21.     QLabel *labPen;
  22.     QComboBox *cbPen;
  23.     QPushButton *btnExit;
  24.     QPushButton *btnChange;
  25.     QGridLayout *buttonLayout;
  26.     QVBoxLayout *layout;
  27. signals:
  28.  
  29. public slots:
  30.  
  31. };
  32.  
  33. #endif // PENCHOOSER_H
To copy to clipboard, switch view to plain text mode 
penChooser.cpp

Qt Code: 
  1. #include "penchooser.h"
  2.  
  3. penChooser::penChooser(QDialog *parent) :
  4.     QDialog(parent)
  5. {
  6.  
  7.     colordialog = new QColorDialog();
  8.     colordialog->setOption(QColorDialog::NoButtons);
  9.  
  10.     labWidth = new QLabel(tr("Pen width:"),this);
  11.  
  12.     sbWidth = new QSpinBox(this);
  13.     sbWidth->setRange(1,50);
  14.     sbWidth->setValue(6);
  15.  
  16.     labPen = new QLabel(tr("Pen type:"),this);
  17.  
  18.     cbPen = new QComboBox(this);
  20.     sl << tr("Standard") << tr("F5 sketching") << tr("F6 User defined")
  21.        << tr("F7 User defined") << tr("F8 User defined");
  22.     cbPen->addItems(sl);
  23.  
  24.     btnExit = new QPushButton(tr("Exit"),this);
  25.  
  26.     btnChange = new QPushButton(tr("Change color"),this);
  27.  
  28.     buttonLayout = new QGridLayout();
  29.     buttonLayout->addWidget(labWidth,0,0);
  30.     buttonLayout->addWidget(labPen,0,1);
  31.     buttonLayout->addWidget(sbWidth,1,0);
  32.     buttonLayout->addWidget(cbPen,1,1);
  33.     buttonLayout->addWidget(btnExit,2,0);
  34.     buttonLayout->addWidget(btnChange,2,1);
  35.  
  36.     layout = new QVBoxLayout();
  37.     layout->addWidget(colordialog);
  38.     layout->addLayout(buttonLayout);
  39.  
  40.     setLayout(layout);
  41.     setWindowTitle(tr("Choose Pen color and width"));
  42.  
  43.     cbPen->setCurrentIndex(cbPen->findText("Pen"));
  44.     sbWidth->setFocus(); 
  45. }
To copy to clipboard, switch view to plain text mode 
In mainwindow.h you'll find
Qt Code: 
  1. penChooser *pc;
To copy to clipboard, switch view to plain text mode 
and in mainwindow.cpp
Qt Code: 
  1. void MainWindow::penPick()
  2. {
  3.     pc = new penChooser();
  4.     pc->colordialog->setCurrentColor(sketchPad->penColor());
  5.     pc->sbWidth->setValue(sketchPad->penWidth());
  6.     pc->cbPen->setCurrentIndex(0);
  7.     pc->setModal(true);
  8.     connect(pc->btnExit, SIGNAL(clicked()), this, SLOT(cancelPenPick()));
  9.     connect(pc->btnChange, SIGNAL(clicked()), this, SLOT(okPenPick()));
  10.     pc->show();
  11. }
To copy to clipboard, switch view to plain text mode 
As said, it worked earlier and used to look like this:
penChooser.jpg

Anyone out there, that can tell me what I'm missing?