I've made the simplest possible drawing App - four files.

I build this in the terminal with qmake; make

Sadly there is no output.

I've tried several things - all the suggestions that Mr Google made did not work

Here's the code:

mini.pro


QT += widgets

CONFIG += console

HEADERS = mini.h
SOURCES = mini.cpp main.cpp

main.cpp


#include <QApplication>

#include "mini.h"

int main(int argc, char *argv[])
{
QApplication app(argc, argv);
Mini my;
my.show();
return app.exec();
}

mini.h

#ifndef MINI_H
#define MINI_H

#include <QWidget>

class Mini : public QWidget
{
Q_OBJECT

public:
Mini(QWidget *parent = 0);

protected:
void paintEvent(QPaintEvent *event) override;

};

#endif

mini.cpp

#include <QtWidgets>
#include <QDebug>

#include "mini.h"

Mini::Mini(QWidget *parent)
: QWidget(parent)
{
setWindowTitle(tr("Mini Graphics"));
resize(300, 200);
}

void Mini:aintEvent(QPaintEvent * )
{
QColor color;
QPainter painter(this);

qDebug() << "painting";

color.setHsv(100, 255, 191);
painter.setPen(color);
painter.drawLine(50, 50, 100, 150);
}