#ifndef MYEDIT_H
#define MYEDIT_H
 
#include <QWidget>
#include <QPlainTextEdit>
 
class MyEdit : public QPlainTextEdit
{
    // Q_OBJECT
public:
    explicit MyEdit (QWidget *parent = nullptr);
 
protected:
    void dragEnterEvent(QDragEnterEvent *event);
    void dropEvent(QDropEvent *event);
};
 
#endif // MYEDIT_H

#include "myedit.h"
 
MyEdit::MyEdit(QWidget *parent) :
    QPlainTextEdit (parent)
{
 
}
 
void MyEdit::dragEnterEvent(QDragEnterEvent *event)
{
    event->setAccepted(true);
 
}
 
void MyEdit::dropEvent(QDropEvent *event)
{
 
}

#ifndef MYBUTTON_H
#define MYBUTTON_H
 
#include <QWidget>
#include <QToolButton>
 
class MyButton : public QToolButton
{
    Q_OBJECT
public:
    explicit MyButton (QWidget *parent = nullptr);
 
signals:
 
public slots:
 
 
    // QWidget interface
protected:
    void mousePressEvent(QMouseEvent *event);
};
 
#endif // MYBUTTON_H

#include "mybutton.h"
 
MyButton::MyButton(QWidget *parent) :
    QToolButton(parent)
{
 
}
 
#include <QDrag>
#include <QMimeData>
void MyButton::mousePressEvent(QMouseEvent *event)
{
    setText ("press");
 
    QMimeData * data = new QMimeData;
    data->setText("nejaky text");
 
    QDrag * drag = new QDrag (this);
    drag->setMimeData(data);
    drag->start();
}

#include "mainwindow.h"
#include "ui_mainwindow.h"
 
#include "mybutton.h"
 
MainWindow::MainWindow(QWidget *parent) :
    QMainWindow(parent),
    ui(new Ui::MainWindow)
{
    ui->setupUi(this);
 
    MyButton * b = new MyButton;
    b->setText("my button");
    ui->mainToolBar->addWidget(b);
}
 
MainWindow::~MainWindow()
{
    delete ui;
}
 
void MainWindow::on_action_Quit_triggered()
{
   close ();
}
 
 
#include <QToolButton>
 
void MainWindow::on_action_Create_triggered()
{
    QToolButton * b = new QToolButton;
    b->setText("button");
    ui->mainToolBar->addWidget(b);
 
    QTreeWidgetItem * t = new QTreeWidgetItem;
    t->setText (0, "abc");
    ui->treeWidget->addTopLevelItem(t);
 
    QTreeWidgetItem * u = new QTreeWidgetItem;
    u->setText (0, "def");
    u->setToolTip (0, "nejaky text");
    u->setForeground(0, QColor ("red"));
    t->addChild(u);
 
    t->setExpanded(true);
}