Question

I have made my own simple widget by deriving from QWidget, and am trying to get it to paint a gradient inside its paintEvent(). I set a breakpoint inside paintEvent, but it never gets called, even when I resize the window etc. The widget is a promoted QWidget from within the designer.
Here is my object code – I am not actually reading the gradient colors yet, just trying to get the paintEvent() to fire first hehe.
First, the header file:

#ifndef GRADIENT_H
#define GRADIENT_H

#include <QBrush>
#include <QPen>
#include <QPixmap>
#include <QWidget>


class Gradient : public QWidget
{
    Q_OBJECT

public:
    Gradient(QWidget *parent = 0);

    QSize minimumSizeHint() const;
    QSize sizeHint() const;

public slots:

protected:
    void paintEvent(QPaintEvent *event);
    void resizeEvent(QResizeEvent *event);

private:

};

#endif // GRADIENT_H

Then, the .cpp:

#include <QtGui>
#include <QPen>

#include "gradient.h"


Gradient::Gradient(QWidget *parent)
    : QWidget(parent)
{

   //setBackgroundRole(QPalette::Base);
    //setAutoFillBackground(true);
}

QSize Gradient::minimumSizeHint() const
{
    return QSize(20, 256);
}

QSize Gradient::sizeHint() const
{
    return QSize(20, 512);
}

void Gradient::resizeEvent(QResizeEvent * /* event */)
{
    //update();
    repaint();
}

void Gradient::paintEvent(QPaintEvent * /* event */)
{
    QPainter painter(this);
    painter.fillRect(rect(), Qt::black);
    painter.setPen(QPen(Qt::blue,1));
   // painter.setBrush(?);

    for (int y = 0; y < height(); ++y)
    {
        painter.save();
      //painter.setPen(); <---here I plan to set different colors from a dynamic table
        painter.translate(0, y);

        painter.drawLine(0, 0, width(), 0);

        painter.restore();
    }
    painter.drawRect(QRect(0, 0, width() - 1, height() - 1));
}

Answer 1

There is no need to call update() or repaint() inside the resizeEvent(). But that shouldn’t break anything either. There must be something wrong with the promoted stuff because that paintEvent() override is correct. I pasted it into a QWidget subclass on my end and it works. Perhaps a clean all and rebuild?