Qt draw pixel data

#include "mywidget.h"
#include <QPainter>

MyWidget::MyWidget(QWidget *parent) : QWidget(parent)
{
    timer = new QTimer(this);   // destruction is made by the Qt framework
    connect(timer, SIGNAL(timeout()), this, SLOT(repaint()));
    timer->start(50);
}

MyWidget::~MyWidget() {
    delete[] buffer;
}


void MyWidget::paintEvent(QPaintEvent *e) {
    fillBuffer();
    QImage img((unsigned char *)buffer, width(), height(), QImage::Format_RGB32);
    QPainter p(this);
    p.drawImage(0, 0, img);
}


void MyWidget::fillBuffer() {
    if (buffer == nullptr) {
        buffer = new uint32_t[width() * height()];
        for(int i = 0; i < width() * height(); i++) {
            buffer[i] = 0;
        }
    }
}