why overriding paintEvent in MainWindow doesn't work

shiner

I just started learning QT. I want overriding the function paintEvent of MainWindow to draw some graphics, But it doesn't work. Thanks for your help.

mainwindow.h

#ifndef MAINWINDOW_H
#define MAINWINDOW_H

#include <QMainWindow>
#include <QPainterPath>
#include <QPainter>
#include <QPaintEvent>
#include <iostream>

namespace Ui {
class MainWindow;
}

class MainWindow : public QMainWindow
{
    Q_OBJECT

public:
    explicit MainWindow(QWidget *parent = 0);
    ~MainWindow();

protected:
    void paintEvent(QPaintEvent *event);

private:
    Ui::MainWindow *ui;
};

#endif // MAINWINDOW_H

mainwindow.cpp

#include "mainwindow.h"
#include "ui_mainwindow.h"

MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
}

MainWindow::~MainWindow()
{
    delete ui;
}

void MainWindow::paintEvent(QPaintEvent *event)
{
    auto rect = event->rect();
    QPainter painter(this);
    painter.setPen(QPen(Qt::red,5, Qt::DashDotLine, Qt::RoundCap));
    QFont font;
    font.setPixelSize(140);
    painter.setFont(font);
    painter.drawText(rect,Qt::AlignRight, "display");

    std::cout << "here" << std::endl;
}

main.cpp

#include "mainwindow.h"
#include <QApplication>

int main(int argc, char *argv[])
{
    QApplication a(argc, argv);
    MainWindow w;

    w.setWindowTitle("main");

    w.show();

    return a.exec();
}

Nothing in the main windows when I run the code.

Christian Ehrlicher

Works fine for me - a big red text 'display' is drawn on the mainwindow.

SGaist

Hi and welcome to devnet,

Since you have a ui file, any chances you have a widget set as central widget of your QMainWindow based class ?