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
 
#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_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;
}
 
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;
 
    startDrag();
    m_eventLoop = new QEventLoop;
    m_eventLoop->exec();
    delete m_eventLoop;
    m_eventLoop = nullptr;
    m_drag = nullptr;
    endDrag();
 
    return m_executed_drop_action;
}
 
void QBasicDrag::cancelDrag()
{
    if (m_eventLoop) {
        cancel();
        m_eventLoop->quit();
    }
}
 
void QBasicDrag::startDrag()
{
    QPoint pos;
#ifndef QT_NO_CURSOR
    pos = QCursor::pos();
    if (pos.x() == int(qInf())) {
        // ### 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();
    m_drag_icon_window->setVisible(false);
}
 
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()
{
    if (m_eventLoop && m_eventLoop->isRunning())
        m_eventLoop->exit();
}
 
void QBasicDrag::updateCursor(Qt::DropAction action)
{
#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
}
 
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() && m_sourceWindow) {
        sendDragLeave(m_sourceWindow);
        m_sourceWindow = nullptr;
    }
}
 
void QSimpleDrag::move(const QPoint &nativeGlobalPos, Qt::MouseButtons buttons,
                       Qt::KeyboardModifiers modifiers)
{
    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)
{
    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