qsimpledrag.cpp

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// Copyright (C) 2016 The Qt Company Ltd.
// SPDX-License-Identifier: LicenseRef-Qt-Commercial OR LGPL-3.0-only OR GPL-2.0-only OR GPL-3.0-only
// Qt-Security score:significant reason:default
 
#include "qsimpledrag_p.h"
 
#include "qbitmap.h"
#include "qdrag.h"
#include "qpixmap.h"
#include "qevent.h"
#include "qfile.h"
#include "qguiapplication.h"
#include "qpoint.h"
#include "qbuffer.h"
#include "qimage.h"
#include "qdir.h"
#include "qimagereader.h"
#include "qimagewriter.h"
#include "qplatformscreen.h"
#include "qplatformwindow.h"
 
#include <QtCore/QEventLoop>
#include <QtCore/QDebug>
#include <QtCore/QLoggingCategory>
 
#include <private/qguiapplication_p.h>
#include <private/qdnd_p.h>
 
#include <private/qshapedpixmapdndwindow_p.h>
#include <private/qhighdpiscaling_p.h>
 
QT_BEGIN_NAMESPACE
 
Q_STATIC_LOGGING_CATEGORY(lcDnd, "qt.gui.dnd")
 
static QWindow* topLevelAt(const QPoint &pos)
{
    const QWindowList list = QGuiApplication::topLevelWindows();
    const auto crend = list.crend();
    for (auto it = list.crbegin(); it != crend; ++it) {
        QWindow *w = *it;
        if (w->isVisible() && w->handle() && w->geometry().contains(pos) && !qobject_cast<QShapedPixmapWindow*>(w))
            return w;
    }
    return nullptr;
}
 
/*!
    \class QBasicDrag
    \brief QBasicDrag is a base class for implementing platform drag and drop.
    \since 5.0
    \internal
    \ingroup qpa
 
    QBasicDrag implements QPlatformDrag::drag() by running a local event loop in which
    it tracks mouse movements and moves the drag icon (QShapedPixmapWindow) accordingly.
    It provides new virtuals allowing for querying whether the receiving window
    (within the Qt application or outside) accepts the drag and sets the state accordingly.
*/
 
QBasicDrag::QBasicDrag()
{
}
 
QBasicDrag::~QBasicDrag()
{
    delete m_drag_icon_window;
}
 
void QBasicDrag::enableEventFilter()
{
    qApp->installEventFilter(this);
}
 
void QBasicDrag::disableEventFilter()
{
    qApp->removeEventFilter(this);
}
 
 
static inline QPoint getNativeMousePos(QEvent *e, QWindow *window)
{
    return QHighDpi::toNativePixels(static_cast<QMouseEvent *>(e)->globalPosition().toPoint(), window);
}
 
bool QBasicDrag::eventFilter(QObject *o, QEvent *e)
{
    Q_UNUSED(o);
 
    if (!m_drag) {
        if (e->type() == QEvent::KeyRelease && static_cast<QKeyEvent*>(e)->key() == Qt::Key_Escape) {
            disableEventFilter();
            exitDndEventLoop();
            return true; // block the key release
        }
        return false;
    }
 
    switch (e->type()) {
        case QEvent::ShortcutOverride:
            // prevent accelerators from firing while dragging
            e->accept();
            return true;
 
        case QEvent::KeyPress:
        case QEvent::KeyRelease:
        {
            QKeyEvent *ke = static_cast<QKeyEvent *>(e);
            if (ke->key() == Qt::Key_Escape && e->type() == QEvent::KeyPress) {
                cancel();
                disableEventFilter();
                exitDndEventLoop();
 
            } else if (ke->modifiers() != QGuiApplication::keyboardModifiers()) {
                move(m_lastPos, QGuiApplication::mouseButtons(), ke->modifiers());
            }
            return true; // Eat all key events
        }
 
        case QEvent::MouseMove:
        {
            m_lastPos = getNativeMousePos(e, m_drag_icon_window);
            auto mouseMove = static_cast<QMouseEvent *>(e);
            move(m_lastPos, mouseMove->buttons(), mouseMove->modifiers());
            return true; // Eat all mouse move events
        }
        case QEvent::MouseButtonRelease:
        {
            QPointer<QObject> objGuard(o);
            disableEventFilter();
            if (canDrop()) {
                QPoint nativePosition = getNativeMousePos(e, m_drag_icon_window);
                auto mouseRelease = static_cast<QMouseEvent *>(e);
                drop(nativePosition, mouseRelease->buttons(), mouseRelease->modifiers());
            } else {
                cancel();
            }
            exitDndEventLoop();
            if (!objGuard)
                return true;
 
            // If a QShapedPixmapWindow (drag feedback) is being dragged along, the
            // mouse event's localPos() will be relative to that, which is useless.
            // We want a position relative to the window where the drag ends, if possible (?).
            // If there is no such window (belonging to this Qt application),
            // make the event relative to the window where the drag started. (QTBUG-66103)
            const QMouseEvent *release = static_cast<QMouseEvent *>(e);
            const QWindow *releaseWindow = topLevelAt(release->globalPosition().toPoint());
            qCDebug(lcDnd) << "mouse released over" << releaseWindow << "after drag from" << m_sourceWindow << "globalPos" << release->globalPosition().toPoint();
            if (!releaseWindow)
                releaseWindow = m_sourceWindow;
            QPointF releaseWindowPos = (releaseWindow ? releaseWindow->mapFromGlobal(release->globalPosition()) : release->globalPosition());
            QMouseEvent *newRelease = new QMouseEvent(release->type(),
                releaseWindowPos, releaseWindowPos, release->globalPosition(),
                release->button(), release->buttons(),
                release->modifiers(), release->source(), release->pointingDevice());
            QCoreApplication::postEvent(o, newRelease);
            return true; // defer mouse release events until drag event loop has returned
        }
        case QEvent::MouseButtonDblClick:
        case QEvent::Wheel:
            return true;
        default:
             break;
    }
    return false;
}
 
Qt::DropAction QBasicDrag::drag(QDrag *o)
{
    m_drag = o;
    m_executed_drop_action = Qt::IgnoreAction;
    m_can_drop = false;
 
    // Create the loop before starting the drag. startDrag() installs the event filter
    // and delivers the first drag events, so the drag can already be cancelled,
    // dropped or destroyed before we get here, and exitDndEventLoop() and cancelDrag()
    // both no-op while m_eventLoop is null. QEventLoop::exec() clears any pending exit
    // when it starts, so we need a flag to avoid losing track of an early exit.
    m_dragEndRequested = false;
    m_eventLoop = new QEventLoop;
    startDrag();
    qCDebug(lcDnd) << "entering drag event loop; drag" << m_drag
                   << "already ended?" << m_dragEndRequested;
    if (m_drag && !m_dragEndRequested)
        m_eventLoop->exec();
    qCDebug(lcDnd) << "left drag event loop; action" << m_executed_drop_action;
    delete m_eventLoop;
    m_eventLoop = nullptr;
    m_drag = nullptr;
    endDrag();
 
    return m_executed_drop_action;
}
 
void QBasicDrag::cancelDrag()
{
    qCDebug(lcDnd) << "cancelling drag";
    if (m_eventLoop) {
        cancel();
        m_dragEndRequested = true;
        m_eventLoop->quit();
    }
}
 
void QBasicDrag::startDrag()
{
    QPoint pos;
#ifndef QT_NO_CURSOR
    pos = QCursor::pos();
    static constexpr QGuiApplicationPrivate::QLastCursorPosition uninitializedCursorPosition;
    if (pos == uninitializedCursorPosition) {
        // ### fixme: no mouse pos registered. Get pos from touch...
        pos = QPoint();
    }
#endif
    m_lastPos = pos;
    recreateShapedPixmapWindow(m_screen, pos);
    enableEventFilter();
}
 
void QBasicDrag::endDrag()
{
}
 
void QBasicDrag::recreateShapedPixmapWindow(QScreen *screen, const QPoint &pos)
{
    delete m_drag_icon_window;
    // ### TODO Check if its really necessary to have m_drag_icon_window
    // when QDrag is used without a pixmap - QDrag::setPixmap()
    m_drag_icon_window = new QShapedPixmapWindow(screen);
 
    m_drag_icon_window->setUseCompositing(m_useCompositing);
    m_drag_icon_window->setPixmap(m_drag->pixmap());
    m_drag_icon_window->setHotspot(m_drag->hotSpot());
    m_drag_icon_window->updateGeometry(pos);
    m_drag_icon_window->setVisible(true);
}
 
void QBasicDrag::cancel()
{
    disableEventFilter();
    restoreCursor();
    // Can be reached before startDrag() has created the icon window, now that the event
    // loop exists for the duration of startDrag() too.
    if (m_drag_icon_window)
        m_drag_icon_window->setVisible(false);
}
 
/*!
  Move the drag label to \a globalPos, which is
  interpreted in device independent coordinates. Typically called from reimplementations of move().
 */
 
void QBasicDrag::moveShapedPixmapWindow(const QPoint &globalPos)
{
    if (m_drag)
        m_drag_icon_window->updateGeometry(globalPos);
}
 
void QBasicDrag::drop(const QPoint &, Qt::MouseButtons, Qt::KeyboardModifiers)
{
    disableEventFilter();
    restoreCursor();
    m_drag_icon_window->setVisible(false);
}
 
void  QBasicDrag::exitDndEventLoop()
{
    m_dragEndRequested = true;
    qCDebug(lcDnd) << "ending drag event loop; running?"
                   << (m_eventLoop && m_eventLoop->isRunning());
    if (m_eventLoop && m_eventLoop->isRunning())
        m_eventLoop->exit();
}
 
void QBasicDrag::updateCursor(Qt::DropAction action)
{
    // In case QDrag is destroyed from a drag event handler, cancel() has
    // already restored the cursor: nothing left to do.
    if (!m_drag)
        return;
 
#ifndef QT_NO_CURSOR
    Qt::CursorShape cursorShape = Qt::ForbiddenCursor;
    if (canDrop()) {
        switch (action) {
        case Qt::CopyAction:
            cursorShape = Qt::DragCopyCursor;
            break;
        case Qt::LinkAction:
            cursorShape = Qt::DragLinkCursor;
            break;
        default:
            cursorShape = Qt::DragMoveCursor;
            break;
        }
    }
 
    QPixmap pixmap = m_drag->dragCursor(action);
 
    if (!m_dndHasSetOverrideCursor) {
        QCursor newCursor = !pixmap.isNull() ? QCursor(pixmap) : QCursor(cursorShape);
        QGuiApplication::setOverrideCursor(newCursor);
        m_dndHasSetOverrideCursor = true;
    } else {
        QCursor *cursor = QGuiApplication::overrideCursor();
        if (!cursor) {
            QGuiApplication::changeOverrideCursor(pixmap.isNull() ? QCursor(cursorShape) : QCursor(pixmap));
        } else {
            if (!pixmap.isNull()) {
                if (cursor->pixmap().cacheKey() != pixmap.cacheKey())
                    QGuiApplication::changeOverrideCursor(QCursor(pixmap));
            } else if (cursorShape != cursor->shape()) {
                QGuiApplication::changeOverrideCursor(QCursor(cursorShape));
            }
        }
    }
#endif
    updateAction(action);
}
 
void QBasicDrag::restoreCursor()
{
#ifndef QT_NO_CURSOR
    if (m_dndHasSetOverrideCursor) {
        QGuiApplication::restoreOverrideCursor();
        m_dndHasSetOverrideCursor = false;
    }
#endif
}
 
static inline QPoint fromNativeGlobalPixels(const QPoint &point)
{
#ifndef QT_NO_HIGHDPISCALING
    QPoint res = point;
    if (QHighDpiScaling::isActive()) {
        for (const QScreen *s : std::as_const(QGuiApplicationPrivate::screen_list)) {
            if (s->handle()->geometry().contains(point)) {
                res = QHighDpi::fromNativePixels(point, s);
                break;
            }
        }
    }
    return res;
#else
    return point;
#endif
}
 
/*!
    \class QSimpleDrag
    \brief QSimpleDrag implements QBasicDrag for Drag and Drop operations within the Qt Application itself.
    \since 5.0
    \internal
    \ingroup qpa
 
    The class checks whether the receiving window is a window of the Qt application
    and sets the state accordingly. It does not take windows of other applications
    into account.
*/
 
QSimpleDrag::QSimpleDrag()
{
}
 
void QSimpleDrag::startDrag()
{
    setExecutedDropAction(Qt::IgnoreAction);
 
    QBasicDrag::startDrag();
    // Here we can be fairly sure that QGuiApplication::mouseButtons/keyboardModifiers() will
    // contain sensible values as startDrag() normally is called from mouse event handlers
    // by QDrag::exec(). A better API would be if we could pass something like "input device
    // pointer" to QDrag::exec(). My guess is that something like that might be required for
    // QTBUG-52430.
    m_sourceWindow = topLevelAt(QCursor::pos());
    m_windowUnderCursor = m_sourceWindow;
    if (m_sourceWindow) {
        auto nativePixelPos = QHighDpi::toNativePixels(QCursor::pos(), m_sourceWindow);
        move(nativePixelPos, QGuiApplication::mouseButtons(), QGuiApplication::keyboardModifiers());
    } else {
        setCanDrop(false);
        updateCursor(Qt::IgnoreAction);
    }
 
    qCDebug(lcDnd) << "drag began from" << m_sourceWindow << "cursor pos" << QCursor::pos() << "can drop?" << canDrop();
}
 
static void sendDragLeave(QWindow *window)
{
    QWindowSystemInterface::handleDrag(window, nullptr, QPoint(), Qt::IgnoreAction, { }, { });
}
 
void QSimpleDrag::cancel()
{
    QBasicDrag::cancel();
    if (drag()) {
        // Leave the window the drag is currently over, which is only the window it
        // started from until the first move() onto another window. Leaving
        // m_sourceWindow instead would send it a second QDragLeaveEvent and leave the
        // window actually under the cursor believing a drag is still in progress.
        if (m_windowUnderCursor)
            sendDragLeave(m_windowUnderCursor);
        m_windowUnderCursor = nullptr;
        m_sourceWindow = nullptr;
    }
}
 
void QSimpleDrag::move(const QPoint &nativeGlobalPos, Qt::MouseButtons buttons,
                       Qt::KeyboardModifiers modifiers)
{
    if (!drag())
        return;
 
    QPoint globalPos = fromNativeGlobalPixels(nativeGlobalPos);
    moveShapedPixmapWindow(globalPos);
    QWindow *window = topLevelAt(globalPos);
 
    if (!window || window != m_windowUnderCursor) {
        if (m_windowUnderCursor)
            sendDragLeave(m_windowUnderCursor);
        m_windowUnderCursor = window;
        if (!window) {
            // QSimpleDrag supports only in-process dnd, we can't drop anywhere else.
            setCanDrop(false);
            updateCursor(Qt::IgnoreAction);
            return;
        }
    }
 
    const QPoint pos = nativeGlobalPos - window->handle()->geometry().topLeft();
    const QPlatformDragQtResponse qt_response = QWindowSystemInterface::handleDrag(
                window, drag()->mimeData(), pos, drag()->supportedActions(),
                buttons, modifiers);
 
    setCanDrop(qt_response.isAccepted());
    updateCursor(qt_response.acceptedAction());
}
 
void QSimpleDrag::drop(const QPoint &nativeGlobalPos, Qt::MouseButtons buttons,
                       Qt::KeyboardModifiers modifiers)
{
    if (!drag())
        return;
 
    QPoint globalPos = fromNativeGlobalPixels(nativeGlobalPos);
 
    QBasicDrag::drop(nativeGlobalPos, buttons, modifiers);
    QWindow *window = topLevelAt(globalPos);
    if (!window)
        return;
 
    const QPoint pos = nativeGlobalPos - window->handle()->geometry().topLeft();
    const QPlatformDropQtResponse response = QWindowSystemInterface::handleDrop(
                window, drag()->mimeData(), pos, drag()->supportedActions(),
                buttons, modifiers);
    if (response.isAccepted()) {
        setExecutedDropAction(response.acceptedAction());
    } else {
        setExecutedDropAction(Qt::IgnoreAction);
    }
}
 
QT_END_NAMESPACE