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

#include <QDrag>
#include <QMimeData>
#include <QDropEvent>
#include <QDragEnterEvent>
#include <QToolButton>
#include <QIcon>
#include <QPainter>

void MainWindow::on_pushButton_pressed ()
{
    QDrag * drag = new QDrag (this);
    QMimeData * mime = new QMimeData;
    mime->setText ("Hello");
    mime->setColorData (QColor ("red"));
    drag->setMimeData (mime);

    QColor c = mime->colorData().value<QColor>();
    QPixmap pixmap (32, 32);
    pixmap.fill (Qt::white);
    QPainter q (&pixmap);
    q.setPen (c);
    q.setBrush (c);
    q.drawEllipse (0, 0, 31, 31);

    drag->setPixmap (pixmap);
    drag->setHotSpot(QPoint (10, 10));

    Qt::DropAction action =
    drag->exec (Qt::CopyAction | Qt::MoveAction | Qt::LinkAction,
                Qt::LinkAction);

    if (action == Qt::MoveAction)
        ui->pushButton->setText ("");
}

void MainWindow::on_pushButton_2_pressed()
{
    QDrag * drag = new QDrag (this);
    QMimeData * mime = new QMimeData;
    mime->setText ("Something");
    mime->setColorData (QColor ("green"));
    drag->setMimeData (mime);
    drag->exec ();
}

class MyButton : public QPushButton
{
protected:
    void dragEnterEvent (QDragEnterEvent * event)
    {
        const QMimeData * mime = event->mimeData ();
        if (mime->hasText () || mime->hasColor ())
           event->setAccepted (true);
    }

    void dropEvent (QDropEvent * event)
    {
        const QMimeData * mime = event->mimeData ();
        if (mime->hasText ())
            this->setText (mime->text());
        if (mime->hasColor())
        {
            QColor c = mime->colorData().value<QColor>();
            QPalette p = this->palette ();
            // p.setColor (QPalette::Button, c);
            p.setColor (QPalette::ButtonText, c);
            this->setPalette (p);

            QPixmap pixmap (32, 32);
            pixmap.fill (Qt::transparent);
            QPainter q (&pixmap);
            q.setPen (c);
            q.setBrush (c);
            // q.drawLine (0, 0, 31, 31);
            q.drawEllipse (0, 0, 31, 31);
            QIcon icon (pixmap);
            this->setIcon (icon);
        }
        event->setDropAction(Qt::MoveAction);
        event->setAccepted(true);
    }
};

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

    MyButton * b = new MyButton;
    b->setText ("My Button");
    b->setParent (this);
    b->setGeometry (200, 100, 200, 100);
    b->setAcceptDrops (true);
}

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