Start creating Qt compoenent

dialog.cpp

#include "dialog.h"

#include <QVBoxLayout>
#include <qxviewer.h>
#include <QLineEdit>
#include <QPushButton>

Dialog::Dialog()
{
    QVBoxLayout *mainLayout = new QVBoxLayout;
    QxViewer *widget = new QxViewer;
    //widget->setBaseSize(400,400);
    QHBoxLayout *hLayout = new QHBoxLayout;
    hLayout->addWidget(new QLineEdit);
    hLayout->addWidget(new QPushButton);
    mainLayout->addLayout(hLayout);
    mainLayout->addWidget(widget);
    //widget.show();

    setLayout(mainLayout);
    mainLayout->setMargin(3);
    resize(400,400);
}

dialog.h

#ifndef DIALOG_H
#define DIALOG_H

#include <QDialog>



class Dialog : public QDialog
{
public:
    Dialog();
};

#endif // DIALOG_H

main.cpp

#include "qxviewer.h"

#include <QApplication>
#include <dialog.h>

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

qxviewer.cpp

#include "qxviewer.h"

#include <QPainter>
#include <QKeyEvent>

QxViewer::QxViewer(QWidget *parent) :
    QWidget(parent)
{
    setWindowTitle(tr("Viewer"));
#if QT_CONFIG(cursor)
    setCursor(Qt::IBeamCursor);
#endif
}

void QxViewer::paintEvent(QPaintEvent * /* event */)
{
    QPainter painter(this);
    painter.fillRect(rect(), Qt::black);
    painter.setPen(*(new QColor(255,34,255,255)));
    painter.drawRect(15,15,100,100);
    painter.setPen(Qt::white);
    painter.drawText(rect(), Qt::AlignCenter, tr("Text on center"));
}


#if QT_CONFIG(wheelevent)
void QxViewer::wheelEvent(QWheelEvent *event)
{
}
#endif

qxviewer.h

#ifndef WIDGET_H
#define WIDGET_H

#include <QWidget>
#include <QScrollBar>

class QxViewer : public QWidget
{
    Q_OBJECT

    QScrollBar vscroll;
    QScrollBar hscroll;
public:
    explicit QxViewer(QWidget *parent = nullptr);
protected:
    void paintEvent(QPaintEvent *event) override;
//    void resizeEvent(QResizeEvent *event) override;
//    void keyPressEvent(QKeyEvent *event) override;
#if QT_CONFIG(wheelevent)
    void wheelEvent(QWheelEvent *event) override;
#endif
//    void mousePressEvent(QMouseEvent *event) override;
//    void mouseMoveEvent(QMouseEvent *event) override;
//    void mouseReleaseEvent(QMouseEvent *event) override;
private:
//    void scroll(int deltaX, int deltaY);
};

#endif // WIDGET_H