- Qt 5.5
- Qt Widgets
- Draggable Text Example
- dragwidget.cpp Example File
- Qt 5.5.1 Reference Documentation

# dragwidget.cpp Example File

draganddrop/draggabletext/dragwidget.cpp

    /****************************************************************************
    **
    ** Copyright (C) 2015 The Qt Company Ltd.
    ** Contact: http://www.qt.io/licensing/
    **
    ** This file is part of the examples of the Qt Toolkit.
    **
    ** $QT_BEGIN_LICENSE:BSD$
    ** You may use this file under the terms of the BSD license as follows:
    **
    ** "Redistribution and use in source and binary forms, with or without
    ** modification, are permitted provided that the following conditions are
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    **     contributors may be used to endorse or promote products derived
    **     from this software without specific prior written permission.
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    #include <QtWidgets>

    #include "draglabel.h"
    #include "dragwidget.h"

    DragWidget::DragWidget(QWidget *parent)
        : QWidget(parent)
    {
        QFile dictionaryFile(":/dictionary/words.txt");
        dictionaryFile.open(QIODevice::ReadOnly);
        QTextStream inputStream(&dictionaryFile);

        int x = 5;
        int y = 5;

        while (!inputStream.atEnd()) {
            QString word;
            inputStream >> word;
            if (!word.isEmpty()) {
                DragLabel *wordLabel = new DragLabel(word, this);
                wordLabel->move(x, y);
                wordLabel->show();
                wordLabel->setAttribute(Qt::WA_DeleteOnClose);
                x += wordLabel->width() + 2;
                if (x >= 245) {
                    x = 5;
                    y += wordLabel->height() + 2;
                }
            }
        }

        /*
        QPalette newPalette = palette();
        newPalette.setColor(QPalette::Window, Qt::white);
        setPalette(newPalette);
        */

        setAcceptDrops(true);
        setMinimumSize(400, qMax(200, y));
        setWindowTitle(tr("Draggable Text"));
    }

    void DragWidget::dragEnterEvent(QDragEnterEvent *event)
    {
        if (event->mimeData()->hasText()) {
            if (event->source() == this) {
                event->setDropAction(Qt::MoveAction);
                event->accept();
            } else {
                event->acceptProposedAction();
            }
        } else {
            event->ignore();
        }
    }

    void DragWidget::dropEvent(QDropEvent *event)
    {
        if (event->mimeData()->hasText()) {
            const QMimeData *mime = event->mimeData();
            QStringList pieces = mime->text().split(QRegExp("\\s+"),
                                 QString::SkipEmptyParts);
            QPoint position = event->pos();
            QPoint hotSpot;

            QList<QByteArray> hotSpotPos = mime->data("application/x-hotspot").split(' ');
            if (hotSpotPos.size() == 2) {
                hotSpot.setX(hotSpotPos.first().toInt());
                hotSpot.setY(hotSpotPos.last().toInt());
            }

            foreach (QString piece, pieces) {
                DragLabel *newLabel = new DragLabel(piece, this);
                newLabel->move(position - hotSpot);
                newLabel->show();
                newLabel->setAttribute(Qt::WA_DeleteOnClose);

                position += QPoint(newLabel->width(), 0);
            }

            if (event->source() == this) {
                event->setDropAction(Qt::MoveAction);
                event->accept();
            } else {
                event->acceptProposedAction();
            }
        } else {
            event->ignore();
        }
        foreach (QObject *child, children()) {
            if (child->inherits("QWidget")) {
                QWidget *widget = static_cast<QWidget *>(child);
                if (!widget->isVisible())
                    widget->deleteLater();
            }
        }
    }

    void DragWidget::mousePressEvent(QMouseEvent *event)
    {
        QLabel *child = static_cast<QLabel*>(childAt(event->pos()));
        if (!child)
            return;

        QPoint hotSpot = event->pos() - child->pos();

        QMimeData *mimeData = new QMimeData;
        mimeData->setText(child->text());
        mimeData->setData("application/x-hotspot",
                          QByteArray::number(hotSpot.x()) + " " + QByteArray::number(hotSpot.y()));

        QPixmap pixmap(child->size());
        child->render(&pixmap);

        QDrag *drag = new QDrag(this);
        drag->setMimeData(mimeData);
        drag->setPixmap(pixmap);
        drag->setHotSpot(hotSpot);

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

        if (dropAction == Qt::MoveAction)
            child->close();
    }