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#include "DragAndDrop/DragDropScroller.h"
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#include <QDragEnterEvent>
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#include <QDragMoveEvent>
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#include <QScrollBar>
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#include <QTimer>
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const int SCROLL_SPEED = 5;
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const int SCROLL_ZONE_SIZE = 50;
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struct DragDropScroller::DragDropScrollerPrivate {
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QList<QScrollArea *> m_ScrollAreas;
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QScrollArea *m_CurrentScrollArea = nullptr;
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std::unique_ptr<QTimer> m_Timer = nullptr;
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enum class ScrollDirection { up, down, unknown };
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ScrollDirection m_Direction = ScrollDirection::unknown;
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explicit DragDropScrollerPrivate() : m_Timer{std::make_unique<QTimer>()}
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{
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m_Timer->setInterval(0);
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}
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};
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DragDropScroller::DragDropScroller(QObject *parent)
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: QObject{parent}, impl{spimpl::make_unique_impl<DragDropScrollerPrivate>()}
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{
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connect(impl->m_Timer.get(), &QTimer::timeout, this, &DragDropScroller::onTimer);
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}
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void DragDropScroller::addScrollArea(QScrollArea *scrollArea)
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{
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impl->m_ScrollAreas << scrollArea;
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scrollArea->viewport()->setAcceptDrops(true);
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}
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void DragDropScroller::removeScrollArea(QScrollArea *scrollArea)
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{
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impl->m_ScrollAreas.removeAll(scrollArea);
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scrollArea->viewport()->setAcceptDrops(false);
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}
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bool DragDropScroller::eventFilter(QObject *obj, QEvent *event)
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{
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if (event->type() == QEvent::DragMove) {
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auto w = static_cast<QWidget *>(obj);
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if (impl->m_CurrentScrollArea && impl->m_CurrentScrollArea->isAncestorOf(w)) {
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auto moveEvent = static_cast<QDragMoveEvent *>(event);
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auto pos = moveEvent->pos();
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if (impl->m_CurrentScrollArea->viewport() != w) {
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auto globalPos = w->mapToGlobal(moveEvent->pos());
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pos = impl->m_CurrentScrollArea->viewport()->mapFromGlobal(globalPos);
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}
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auto isInTopZone = pos.y() > impl->m_CurrentScrollArea->viewport()->size().height()
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- SCROLL_ZONE_SIZE;
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auto isInBottomZone = pos.y() < SCROLL_ZONE_SIZE;
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if (!isInTopZone && !isInBottomZone) {
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impl->m_Direction = DragDropScrollerPrivate::ScrollDirection::unknown;
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impl->m_Timer->stop();
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}
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else if (!impl->m_Timer->isActive()) {
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impl->m_Direction = isInTopZone ? DragDropScrollerPrivate::ScrollDirection::up
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: DragDropScrollerPrivate::ScrollDirection::down;
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impl->m_Timer->start();
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}
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}
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}
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else if (event->type() == QEvent::DragEnter) {
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auto w = static_cast<QWidget *>(obj);
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for (auto scrollArea : impl->m_ScrollAreas) {
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if (impl->m_CurrentScrollArea != scrollArea && scrollArea->isAncestorOf(w)) {
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auto enterEvent = static_cast<QDragEnterEvent *>(event);
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enterEvent->acceptProposedAction();
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enterEvent->setDropAction(Qt::IgnoreAction);
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impl->m_CurrentScrollArea = scrollArea;
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break;
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}
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}
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}
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else if (event->type() == QEvent::DragLeave) {
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if (impl->m_CurrentScrollArea) {
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if (!QRect(QPoint(), impl->m_CurrentScrollArea->size())
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.contains(impl->m_CurrentScrollArea->mapFromGlobal(QCursor::pos()))) {
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impl->m_CurrentScrollArea = nullptr;
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impl->m_Direction = DragDropScrollerPrivate::ScrollDirection::unknown;
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impl->m_Timer->stop();
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}
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}
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}
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else if (event->type() == QEvent::Drop) {
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if (impl->m_CurrentScrollArea) {
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impl->m_CurrentScrollArea = nullptr;
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impl->m_Direction = DragDropScrollerPrivate::ScrollDirection::unknown;
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impl->m_Timer->stop();
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}
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}
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return false;
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}
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void DragDropScroller::onTimer()
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{
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if (impl->m_CurrentScrollArea) {
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auto mvt = 0;
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switch (impl->m_Direction) {
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case DragDropScrollerPrivate::ScrollDirection::up:
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mvt = SCROLL_SPEED;
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break;
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case DragDropScrollerPrivate::ScrollDirection::down:
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mvt = -SCROLL_SPEED;
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break;
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default:
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break;
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}
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impl->m_CurrentScrollArea->verticalScrollBar()->setValue(
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impl->m_CurrentScrollArea->verticalScrollBar()->value() + mvt);
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}
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}
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