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// Copyright (C) 2025 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR GPL-3.0-only
#include <QtCore/QDebug>
#include <QtCore/QMimeData>
#include <QtGui/QDrag>
#include <QtGui/QMouseEvent>
#include <QtGui/QPixmap>
#include <QtWidgets/QApplication>
#include <QtWidgets/QLabel>
#include <QtWidgets/QMainWindow>
#include <QtWidgets/QVBoxLayout>
#include <QtWidgets/QWidget>
using namespace Qt::Literals;
class DraggableLabel : public QLabel
{
public:
explicit DraggableLabel(const QString &text, QWidget *parent = nullptr) : QLabel(text, parent)
{
setFrameShape(QFrame::Panel);
setFrameShadow(QFrame::Raised);
setMinimumHeight(40);
}
protected:
void mousePressEvent(QMouseEvent *event) override
{
qDebug() << "DraggableLabel: Mouse Press Event";
m_dragStartPosition = event->pos();
}
void mouseMoveEvent(QMouseEvent *event) override
{
qDebug() << "DraggableLabel: Mouse Move Event";
if ((event->pos() - m_dragStartPosition).manhattanLength()
< QApplication::startDragDistance())
return;
qDebug() << "DraggableLabel: Starting drag...";
QDrag *drag = new QDrag(this);
QMimeData *mimeData = new QMimeData;
mimeData->setText(this->text());
drag->setMimeData(mimeData);
QPixmap pixmap = this->grab();
drag->setPixmap(pixmap);
drag->setHotSpot(event->pos() - this->rect().topLeft());
drag->exec(Qt::CopyAction | Qt::MoveAction);
}
private:
QPoint m_dragStartPosition;
};
class DragDropWidget : public QWidget
{
public:
explicit DragDropWidget(QWidget *parent = nullptr) : QWidget(parent)
{
setAcceptDrops(true);
setMouseTracking(true); // Needed for mouseMoveEvent without button press
setMinimumSize(200, 200);
setAutoFillBackground(true);
QPalette pal = palette();
pal.setColor(QPalette::Window, Qt::lightGray);
setPalette(pal);
}
protected:
void mousePressEvent(QMouseEvent *event) override
{
qDebug() << "DropArea: Mouse Press Event at:" << event->pos() << "with button"
<< event->button() << event->buttons();
m_dragStartPosition = event->pos();
QWidget::mousePressEvent(event);
}
void mouseMoveEvent(QMouseEvent *event) override
{
qDebug() << "DropArea: Mouse Move Event at:" << event->pos();
if (!(event->buttons() & Qt::LeftButton))
return;
if ((event->pos() - m_dragStartPosition).manhattanLength()
< QApplication::startDragDistance())
return;
QDrag *drag = new QDrag(this);
QMimeData *mimeData = new QMimeData;
mimeData->setText(u"This is a test drag from the drop area."_s);
drag->setMimeData(mimeData);
qDebug() << "DropArea: Starting drag...";
drag->exec(Qt::CopyAction | Qt::MoveAction);
}
void mouseReleaseEvent(QMouseEvent *event) override
{
qDebug() << "DropArea: Mouse Release Event at:" << event->pos() << "with button"
<< event->button() << event->buttons();
QWidget::mouseReleaseEvent(event);
}
void mouseDoubleClickEvent(QMouseEvent *event) override
{
qDebug() << "DropArea: Mouse Double Click Event at:" << event->pos();
QWidget::mouseDoubleClickEvent(event);
}
void wheelEvent(QWheelEvent *event) override
{
qDebug() << "DropArea: Wheel Event with delta:" << event->angleDelta();
QWidget::wheelEvent(event);
}
void dragEnterEvent(QDragEnterEvent *event) override
{
qDebug() << "DropArea: Drag Enter Event";
if (event->mimeData()->hasText())
event->acceptProposedAction();
}
void dragMoveEvent(QDragMoveEvent *event) override
{
qDebug() << "DropArea: Drag Move Event at:" << event->position();
event->accept();
}
void dragLeaveEvent(QDragLeaveEvent *event) override
{
qDebug() << "DropArea: Drag Leave Event";
event->accept();
}
void dropEvent(QDropEvent *event) override
{
qDebug() << "DropArea: Drop Event at:" << event->position() << "with buttons"
<< event->buttons();
if (event->mimeData()->hasText()) {
qDebug() << "DropArea: Dropped text:" << event->mimeData()->text();
event->acceptProposedAction();
}
}
private:
QPoint m_dragStartPosition;
};
int main(int argc, char *argv[])
{
QApplication a(argc, argv);
QMainWindow w;
QWidget *centralWidget = new QWidget;
QVBoxLayout *layout = new QVBoxLayout(centralWidget);
DraggableLabel *draggableLabel = new DraggableLabel(u"Drag This Label!"_s);
QLabel *infoLabel = new QLabel(u"Drag the label above into the grey drop area below. You can "
u"also drag from the grey area itself."_s);
infoLabel->setWordWrap(true);
DragDropWidget *dragDropWidget = new DragDropWidget;
layout->addWidget(draggableLabel); // Add the draggable label
layout->addWidget(infoLabel);
layout->addWidget(dragDropWidget);
w.setCentralWidget(centralWidget);
w.setWindowTitle(u"Qt Drag and Drop Test"_s);
w.show();
return a.exec();
}
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