breeze/kstyle/breezewindowmanager.cpp

/*
 * breezewindowmanager.cpp
 * pass some window mouse press/release/move event actions to window manager
 * Largely inspired from BeSpin style
 *
 * SPDX-FileCopyrightText: 2007 Thomas Luebking <thomas.luebking@web.de>
 * SPDX-FileCopyrightText: 2014 Hugo Pereira Da Costa <hugo.pereira@free.fr>
 *
 * SPDX-License-Identifier: GPL-2.0-or-later OR MIT
 */

#include "breezewindowmanager.h"
#include "breezehelper.h"
#include "breezepropertynames.h"

#include <QComboBox>
#include <QDialog>
#include <QDockWidget>
#include <QGraphicsView>
#include <QGroupBox>
#include <QLabel>
#include <QListView>
#include <QMainWindow>
#include <QMdiSubWindow>
#include <QMenuBar>
#include <QMouseEvent>
#include <QProgressBar>
#include <QScreen>
#include <QScrollBar>
#include <QStatusBar>
#include <QStyle>
#include <QStyleOptionGroupBox>
#include <QTabBar>
#include <QTabWidget>
#include <QToolBar>
#include <QToolButton>
#include <QTreeView>

#include <QTextStream>

// needed to deal with device pixel ratio
#include <QWindow>

#if BREEZE_HAVE_QTQUICK
// needed to enable dragging from QQuickWindows
#include <QQuickRenderControl>
#include <QQuickWindow>
#endif

namespace Util
{
template<class T>
inline T makeT(std::initializer_list<typename T::key_type> &&reference)
{
    return T(std::move(reference));
}
}

namespace Breeze
{
//* provide application-wise event filter
/**
it us used to unlock dragging and make sure event look is properly restored
after a drag has occurred
*/
class AppEventFilter : public QObject
{
public:
    //* constructor
    explicit AppEventFilter(WindowManager *parent)
        : QObject(parent)
        , _parent(parent)
    {
    }

    //* event filter
    bool eventFilter(QObject *object, QEvent *event) override
    {
        if (event->type() == QEvent::MouseButtonRelease) {
            // stop drag timer
            if (_parent->_dragTimer.isActive()) {
                _parent->resetDrag();
            }

            // unlock
            if (_parent->isLocked()) {
                _parent->setLocked(false);
            }
        }

        if (!_parent->enabled())
            return false;

        /*
        if a drag is in progress, the widget will not receive any event
        we trigger on the first MouseMove or MousePress events that are received
        by any widget in the application to detect that the drag is finished
        */
        if (_parent->_dragInProgress && _parent->_target && (event->type() == QEvent::MouseMove || event->type() == QEvent::MouseButtonPress)) {
            return appMouseEvent(object, event);
        }

        return false;
    }

protected:
    //* application-wise event.
    /** needed to catch end of XMoveResize events */
    bool appMouseEvent(QObject *, QEvent *event)
    {
        Q_UNUSED(event);

        /*
        post some mouseRelease event to the target, in order to counter balance
        the mouse press that triggered the drag. Note that it triggers a resetDrag
        */
        QMouseEvent mouseEvent(QEvent::MouseButtonRelease, _parent->_dragPoint, Qt::LeftButton, Qt::LeftButton, Qt::NoModifier);
        qApp->sendEvent(_parent->_target.data(), &mouseEvent);

        return false;
    }

private:
    //* parent
    WindowManager *_parent = nullptr;
};

//_____________________________________________________________
WindowManager::WindowManager(QObject *parent)
    : QObject(parent)
{
    // install application wise event filter
    _appEventFilter = new AppEventFilter(this);
    qApp->installEventFilter(_appEventFilter);
}

//_____________________________________________________________
void WindowManager::initialize()
{
    setEnabled(StyleConfigData::windowDragMode() != StyleConfigData::WD_NONE);
    setDragMode(StyleConfigData::windowDragMode());
    setDragDistance(QApplication::startDragDistance());
    setDragDelay(QApplication::startDragTime());

    initializeWhiteList();
    initializeBlackList();
}

//_____________________________________________________________
void WindowManager::registerWidget(QWidget *widget)
{
    if (isBlackListed(widget) || isDragable(widget) || widget->inherits("QQuickWidget")) {
        /*
        install filter for dragable widgets.
        also install filter for blacklisted widgets
        to be able to catch the relevant events and prevent
        the drag to happen
        */
        widget->removeEventFilter(this);
        widget->installEventFilter(this);
    }
}

#if BREEZE_HAVE_QTQUICK
//_____________________________________________________________
void WindowManager::registerQuickItem(QQuickItem *item)
{
    if (!item)
        return;

    if (auto window = item->window()) {
        auto contentItem = window->contentItem();
        contentItem->setAcceptedMouseButtons(Qt::LeftButton);
        contentItem->removeEventFilter(this);
        contentItem->installEventFilter(this);
    }
}
#endif

//_____________________________________________________________
void WindowManager::unregisterWidget(QWidget *widget)
{
    if (widget)
        widget->removeEventFilter(this);
}

//_____________________________________________________________
void WindowManager::initializeWhiteList()
{
    _whiteList = Util::makeT<ExceptionSet>({ExceptionId(QStringLiteral("MplayerWindow")),
                                            ExceptionId(QStringLiteral("ViewSliders@kmix")),
                                            ExceptionId(QStringLiteral("Sidebar_Widget@konqueror"))});

    foreach (const QString &exception, StyleConfigData::windowDragWhiteList()) {
        ExceptionId id(exception);
        if (!id.className().isEmpty()) {
            _whiteList.insert(ExceptionId(exception));
        }
    }
}

//_____________________________________________________________
void WindowManager::initializeBlackList()
{
    _blackList = Util::makeT<ExceptionSet>(
        {ExceptionId(QStringLiteral("CustomTrackView@kdenlive")), ExceptionId(QStringLiteral("MuseScore")), ExceptionId(QStringLiteral("KGameCanvasWidget"))});

    foreach (const QString &exception, StyleConfigData::windowDragBlackList()) {
        ExceptionId id(exception);
        if (!id.className().isEmpty()) {
            _blackList.insert(ExceptionId(exception));
        }
    }
}

//_____________________________________________________________
bool WindowManager::eventFilter(QObject *object, QEvent *event)
{
    if (!enabled())
        return false;

    switch (event->type()) {
    case QEvent::MouseButtonPress:
        return mousePressEvent(object, event);
        break;

    case QEvent::MouseMove:
        if (object == _target.data()
#if BREEZE_HAVE_QTQUICK
            || object == _quickTarget.data()
#endif
        )
            return mouseMoveEvent(object, event);
        break;

    case QEvent::MouseButtonRelease:
        if (_target
#if BREEZE_HAVE_QTQUICK
            || _quickTarget
#endif
        )
            return mouseReleaseEvent(object, event);
        break;

    default:
        break;
    }

    return false;
}

//_____________________________________________________________
void WindowManager::timerEvent(QTimerEvent *event)
{
    if (event->timerId() == _dragTimer.timerId()) {
        _dragTimer.stop();
        setLocked(false);
        if (_target)
            startDrag(_target.data()->window()->windowHandle());
#if BREEZE_HAVE_QTQUICK
        else if (_quickTarget) {
            _quickTarget.data()->ungrabMouse();
            startDrag(_quickTarget.data()->window());
        }
#endif
        resetDrag();
    } else {
        return QObject::timerEvent(event);
    }
}

//_____________________________________________________________
bool WindowManager::mousePressEvent(QObject *object, QEvent *event)
{
    // cast event and check buttons/modifiers
    auto mouseEvent = static_cast<QMouseEvent *>(event);
    if (mouseEvent->source() != Qt::MouseEventNotSynthesized) {
        return false;
    }
    if (!(mouseEvent->modifiers() == Qt::NoModifier && mouseEvent->button() == Qt::LeftButton)) {
        return false;
    }

    // If we are in a QQuickWidget we don't want to ever do dragging from a qwidget in the
    // hyerarchy, but only from an internal item, if any. If any event handler will manage
    // the event, we don't want the drag to start
    if (object->inherits("QQuickWidget")) {
        _eventInQQuickWidget = true;
        event->setAccepted(false);
        return false;
    } else {
        _eventInQQuickWidget = false;
    }

    // check lock
    if (isLocked())
        return false;
    else
        setLocked(true);

#if BREEZE_HAVE_QTQUICK
    // check QQuickItem - we can immediately start drag, because QQuickWindow's contentItem
    // only receives mouse events that weren't handled by children
    if (auto item = qobject_cast<QQuickItem *>(object)) {
        _quickTarget = item;
        _dragPoint = mouseEvent->pos();
        _globalDragPoint = mouseEvent->globalPos();

        if (_dragTimer.isActive())
            _dragTimer.stop();
        _dragTimer.start(_dragDelay, this);

        return true;
    }
#endif

    if (_eventInQQuickWidget) {
        event->setAccepted(true);
        return false;
    }
    _eventInQQuickWidget = false;

    // cast to widget
    auto widget = static_cast<QWidget *>(object);

    // check if widget can be dragged from current position
    if (isBlackListed(widget) || !canDrag(widget))
        return false;

    // retrieve widget's child at event position
    auto position(mouseEvent->pos());
    auto child = widget->childAt(position);
    if (!canDrag(widget, child, position))
        return false;

    // save target and drag point
    _target = widget;
    _dragPoint = position;
    _globalDragPoint = mouseEvent->globalPos();
    _dragAboutToStart = true;

    // send a move event to the current child with same position
    // if received, it is caught to actually start the drag
    auto localPoint(_dragPoint);
    if (child)
        localPoint = child->mapFrom(widget, localPoint);
    else
        child = widget;
    QMouseEvent localMouseEvent(QEvent::MouseMove, localPoint, Qt::LeftButton, Qt::LeftButton, Qt::NoModifier);
    qApp->sendEvent(child, &localMouseEvent);

    // never eat event
    return false;
}

//_____________________________________________________________
bool WindowManager::mouseMoveEvent(QObject *object, QEvent *event)
{
    Q_UNUSED(object);

    // stop timer
    if (_dragTimer.isActive())
        _dragTimer.stop();

    // cast event and check drag distance
    auto mouseEvent = static_cast<QMouseEvent *>(event);
    if (mouseEvent->source() != Qt::MouseEventNotSynthesized) {
        return false;
    }
    if (!_dragInProgress) {
        if (_dragAboutToStart) {
            if (mouseEvent->pos() == _dragPoint) {
                // start timer,
                _dragAboutToStart = false;
                if (_dragTimer.isActive())
                    _dragTimer.stop();
                _dragTimer.start(_dragDelay, this);

            } else
                resetDrag();

        } else if (QPoint(mouseEvent->globalPos() - _globalDragPoint).manhattanLength() >= _dragDistance) {
            _dragTimer.start(0, this);
        }

        return true;

    } else
        return false;
}

//_____________________________________________________________
bool WindowManager::mouseReleaseEvent(QObject *object, QEvent *event)
{
    Q_UNUSED(object);
    Q_UNUSED(event);
    resetDrag();
    return false;
}

//_____________________________________________________________
bool WindowManager::isDragable(QWidget *widget)
{
    // check widget
    if (!widget)
        return false;

    // accepted default types
    if ((qobject_cast<QDialog *>(widget) && widget->isWindow()) || (qobject_cast<QMainWindow *>(widget) && widget->isWindow())
        || qobject_cast<QGroupBox *>(widget)) {
        return true;
    }

    // more accepted types, provided they are not dock widget titles
    if ((qobject_cast<QMenuBar *>(widget) || qobject_cast<QTabBar *>(widget) || qobject_cast<QStatusBar *>(widget) || qobject_cast<QToolBar *>(widget))
        && !isDockWidgetTitle(widget)) {
        return true;
    }

    if (widget->inherits("KScreenSaver") && widget->inherits("KCModule")) {
        return true;
    }

    if (isWhiteListed(widget)) {
        return true;
    }

    // flat toolbuttons
    if (auto toolButton = qobject_cast<QToolButton *>(widget)) {
        if (toolButton->autoRaise())
            return true;
    }

    // viewports
    /*
    one needs to check that
    1/ the widget parent is a scrollarea
    2/ it matches its parent viewport
    3/ the parent is not blacklisted
    */
    if (auto listView = qobject_cast<QListView *>(widget->parentWidget())) {
        if (listView->viewport() == widget && !isBlackListed(listView))
            return true;
    }

    if (auto treeView = qobject_cast<QTreeView *>(widget->parentWidget())) {
        if (treeView->viewport() == widget && !isBlackListed(treeView))
            return true;
    }

    /*
    catch labels in status bars.
    this is because of kstatusbar
    who captures buttonPress/release events
    */
    if (auto label = qobject_cast<QLabel *>(widget)) {
        if (label->textInteractionFlags().testFlag(Qt::TextSelectableByMouse))
            return false;

        QWidget *parent = label->parentWidget();
        while (parent) {
            if (qobject_cast<QStatusBar *>(parent))
                return true;
            parent = parent->parentWidget();
        }
    }

    return false;
}

//_____________________________________________________________
bool WindowManager::isBlackListed(QWidget *widget)
{
    // check against noAnimations property
    const auto propertyValue(widget->property(PropertyNames::noWindowGrab));
    if (propertyValue.isValid() && propertyValue.toBool())
        return true;

    // list-based blacklisted widgets
    const auto appName(qApp->applicationName());
    foreach (const ExceptionId &id, _blackList) {
        if (!id.appName().isEmpty() && id.appName() != appName)
            continue;
        if (id.className() == QStringLiteral("*") && !id.appName().isEmpty()) {
            // if application name matches and all classes are selected
            // disable the grabbing entirely
            setEnabled(false);
            return true;
        }
        if (widget->inherits(id.className().toLatin1().data()))
            return true;
    }

    return false;
}

//_____________________________________________________________
bool WindowManager::isWhiteListed(QWidget *widget) const
{
    const auto appName(qApp->applicationName());
    foreach (const ExceptionId &id, _whiteList) {
        if (!(id.appName().isEmpty() || id.appName() == appName))
            continue;
        if (widget->inherits(id.className().toLatin1().data()))
            return true;
    }

    return false;
}

//_____________________________________________________________
bool WindowManager::canDrag(QWidget *widget)
{
    // check if enabled
    if (!enabled())
        return false;

    // assume isDragable widget is already passed
    // check some special cases where drag should not be effective

    // check mouse grabber
    if (QWidget::mouseGrabber())
        return false;

    /*
    check cursor shape.
    Assume that a changed cursor means that some action is in progress
    and should prevent the drag
    */
    if (widget->cursor().shape() != Qt::ArrowCursor)
        return false;

    // accept
    return true;
}

//_____________________________________________________________
bool WindowManager::canDrag(QWidget *widget, QWidget *child, const QPoint &position)
{
    // retrieve child at given position and check cursor again
    if (child && child->cursor().shape() != Qt::ArrowCursor)
        return false;

    /*
    check against children from which drag should never be enabled,
    even if mousePress/Move has been passed to the parent
    */
    if (child && (qobject_cast<QComboBox *>(child) || qobject_cast<QProgressBar *>(child) || qobject_cast<QScrollBar *>(child))) {
        return false;
    }

    // tool buttons
    if (auto toolButton = qobject_cast<QToolButton *>(widget)) {
        if (dragMode() == StyleConfigData::WD_MINIMAL && !qobject_cast<QToolBar *>(widget->parentWidget()))
            return false;
        return toolButton->autoRaise() && !toolButton->isEnabled();
    }

    // check menubar
    if (auto menuBar = qobject_cast<QMenuBar *>(widget)) {
        // do not drag from menubars embedded in Mdi windows
        if (findParent<QMdiSubWindow *>(widget))
            return false;

        // check if there is an active action
        if (menuBar->activeAction() && menuBar->activeAction()->isEnabled())
            return false;

        // check if action at position exists and is enabled
        if (auto action = menuBar->actionAt(position)) {
            if (action->isSeparator())
                return true;
            if (action->isEnabled())
                return false;
        }

        // return true in all other cases
        return true;
    }

    /*
    in MINIMAL mode, anything that has not been already accepted
    and does not come from a toolbar is rejected
    */
    if (dragMode() == StyleConfigData::WD_MINIMAL) {
        if (qobject_cast<QToolBar *>(widget))
            return true;
        else
            return false;
    }

    /* following checks are relevant only for WD_FULL mode */

    // tabbar. Make sure no tab is under the cursor
    if (auto tabBar = qobject_cast<QTabBar *>(widget)) {
        return tabBar->tabAt(position) == -1;
    }

    /*
    check groupboxes
    prevent drag if unchecking grouboxes
    */
    if (auto groupBox = qobject_cast<QGroupBox *>(widget)) {
        // non checkable group boxes are always ok
        if (!groupBox->isCheckable())
            return true;

        // gather options to retrieve checkbox subcontrol rect
        QStyleOptionGroupBox opt;
        opt.initFrom(groupBox);
        if (groupBox->isFlat())
            opt.features |= QStyleOptionFrame::Flat;
        opt.lineWidth = 1;
        opt.midLineWidth = 0;
        opt.text = groupBox->title();
        opt.textAlignment = groupBox->alignment();
        opt.subControls = (QStyle::SC_GroupBoxFrame | QStyle::SC_GroupBoxCheckBox);
        if (!groupBox->title().isEmpty())
            opt.subControls |= QStyle::SC_GroupBoxLabel;

        opt.state |= (groupBox->isChecked() ? QStyle::State_On : QStyle::State_Off);

        // check against groupbox checkbox
        if (groupBox->style()->subControlRect(QStyle::CC_GroupBox, &opt, QStyle::SC_GroupBoxCheckBox, groupBox).contains(position)) {
            return false;
        }

        // check against groupbox label
        if (!groupBox->title().isEmpty()
            && groupBox->style()->subControlRect(QStyle::CC_GroupBox, &opt, QStyle::SC_GroupBoxLabel, groupBox).contains(position)) {
            return false;
        }

        return true;
    }

    // labels
    if (auto label = qobject_cast<QLabel *>(widget)) {
        if (label->textInteractionFlags().testFlag(Qt::TextSelectableByMouse))
            return false;
    }

    // abstract item views
    QAbstractItemView *itemView(nullptr);
    if ((itemView = qobject_cast<QListView *>(widget->parentWidget())) || (itemView = qobject_cast<QTreeView *>(widget->parentWidget()))) {
        if (widget == itemView->viewport()) {
            // QListView
            if (itemView->frameShape() != QFrame::NoFrame)
                return false;
            else if (itemView->selectionMode() != QAbstractItemView::NoSelection && itemView->selectionMode() != QAbstractItemView::SingleSelection
                     && itemView->model() && itemView->model()->rowCount())
                return false;
            else if (itemView->model() && itemView->indexAt(position).isValid())
                return false;
        }

    } else if ((itemView = qobject_cast<QAbstractItemView *>(widget->parentWidget()))) {
        if (widget == itemView->viewport()) {
            // QAbstractItemView
            if (itemView->frameShape() != QFrame::NoFrame)
                return false;
            else if (itemView->indexAt(position).isValid())
                return false;
        }

    } else if (auto graphicsView = qobject_cast<QGraphicsView *>(widget->parentWidget())) {
        if (widget == graphicsView->viewport()) {
            // QGraphicsView
            if (graphicsView->frameShape() != QFrame::NoFrame)
                return false;
            else if (graphicsView->dragMode() != QGraphicsView::NoDrag)
                return false;
            else if (graphicsView->itemAt(position))
                return false;
        }
    }

    return true;
}

//____________________________________________________________
void WindowManager::resetDrag()
{
    _target.clear();
#if BREEZE_HAVE_QTQUICK
    _quickTarget.clear();
#endif
    if (_dragTimer.isActive())
        _dragTimer.stop();
    _dragPoint = QPoint();
    _globalDragPoint = QPoint();
    _dragAboutToStart = false;
    _dragInProgress = false;
}

//____________________________________________________________
void WindowManager::startDrag(QWindow *window)
{
    if (!(enabled() && window))
        return;
    if (QWidget::mouseGrabber())
        return;

#if BREEZE_HAVE_QTQUICK
    if (_quickTarget) {
        if (QQuickWindow *qw = qobject_cast<QQuickWindow *>(window)) {
            QWindow *renderWindow = QQuickRenderControl::renderWindowFor(qw);
            if (renderWindow) {
                _dragInProgress = renderWindow->startSystemMove();
            } else {
                _dragInProgress = window->startSystemMove();
            }
        }
    } else
#endif
    {
        _dragInProgress = window->startSystemMove();
    }
}

//____________________________________________________________
bool WindowManager::isDockWidgetTitle(const QWidget *widget) const
{
    if (!widget)
        return false;
    if (auto dockWidget = qobject_cast<const QDockWidget *>(widget->parent())) {
        return widget == dockWidget->titleBarWidget();

    } else
        return false;
}

}