plasma-framework/extenders/extender.cpp

/*
 * Copyright 2008, 2009 by Rob Scheepmaker <r.scheepmaker@student.utwente.nl>
 *
 * This library is free software; you can redistribute it and/or
 * modify it under the terms of the GNU Lesser General Public
 * License as published by the Free Software Foundation; either
 * version 2.1 of the License, or (at your option) any later version.
 *
 * This library is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
 * Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public
 * License along with this library; if not, write to the Free Software
 * Foundation, Inc., 51 Franklin St, Fifth Floor,
 * Boston, MA  02110-1301  USA
 */

#include "extender.h"

#include <QAction>
#include <QLabel>
#include <QGraphicsSceneDragDropEvent>
#include <QGraphicsGridLayout>
#include <QGraphicsLinearLayout>
#include <QPainter>

#include "applet.h"
#include "containment.h"
#include "corona.h"
#include "extendergroup.h"
#include "extenderitem.h"
#include "framesvg.h"
#include "paintutils.h"
#include "popupapplet.h"
#include "svg.h"
#include "theme.h"
#include "widgets/label.h"

#include "private/applet_p.h"
#include "private/applethandle_p.h"
#include "private/extender_p.h"
#include "private/extenderapplet_p.h"
#include "private/extenderitem_p.h"
#include "private/extenderitemmimedata_p.h"
#include "private/popupapplet_p.h"

namespace Plasma
{

Spacer::Spacer(QGraphicsItem *parent)
    : QGraphicsWidget(parent)
{
}

Spacer::~Spacer()
{
}

void Spacer::setMargins(qreal left, qreal top, qreal right, qreal bottom)
{
    m_left = left;
    m_top = top;
    m_right = right;
    m_bottom = bottom;
}


void Spacer::paint(QPainter *painter, const QStyleOptionGraphicsItem *option, QWidget *widget)
{
    Q_UNUSED(option)
    Q_UNUSED(widget)

    painter->setRenderHint(QPainter::Antialiasing);
    QPainterPath p = Plasma::PaintUtils::roundedRectangle(
                        contentsRect().adjusted(m_left, m_top, -m_right, -m_bottom), 4);

    QColor c = Plasma::Theme::defaultTheme()->color(Plasma::Theme::TextColor);
    c.setAlphaF(0.3);
    painter->fillPath(p, c);
}


Extender::Extender(Applet *applet)
        : QGraphicsWidget(applet),
          d(new ExtenderPrivate(applet, this))
{
    //At multiple places in the extender code, we make the assumption that an applet doesn't have
    //more then one extender. If a second extender is created, destroy the first one to avoid leaks.
    if (applet->d->extender) {
        kWarning() << "Applet already has an extender, and can have only one extender."
                   << "The previous extender will be destroyed.";
        delete applet->d->extender.data();
    } else if (PopupApplet *popup = qobject_cast<PopupApplet *>(applet)) {
        if (!popup->d->graphicsWidget) {
            // ensure the popup gets a dialog with us as the graphics widget
            popup->d->popupConstraintsEvent(SizeConstraint);
        }
    }

    applet->d->extender = this;
    setSizePolicy(QSizePolicy::Expanding, QSizePolicy::Expanding);

    setContentsMargins(0, 0, 0, 0);
    d->layout = new QGraphicsLinearLayout(this);
    d->layout->setOrientation(Qt::Vertical);
    d->layout->setContentsMargins(0, 0, 0, 0);
    d->layout->setSpacing(0);
    setLayout(d->layout);

    d->loadExtenderItems();

    setAcceptDrops(true);
}

Extender::~Extender()
{
    d->destroying = true;

    // when deleting items that are connected to us, it can happen that
    // other items which are in groups may get deleted as well. so we first
    // build a new list of guarded pointers, and then use that list. that
    // way when items are deleted behind our back, we are still safe.
    // FIXME: having groups and items in the same collection is probably a mistake,
    // so would be a good candidate for a refactoring exercise
    QList<QWeakPointer<ExtenderItem> > guardedItems;

    foreach (ExtenderItem *item, d->attachedExtenderItems) {
        guardedItems << QWeakPointer<ExtenderItem>(item);
    }

    d->attachedExtenderItems.clear();

    foreach (const QWeakPointer<ExtenderItem> &guardedItem, guardedItems) {
        ExtenderItem *item = guardedItem.data();
        if (item) {
            item->disconnect(this);
            delete item;
        }
    }


    delete d;
}

void Extender::setEmptyExtenderMessage(const QString &message)
{
    d->emptyExtenderMessage = message;

    if (d->emptyExtenderLabel) {
        d->emptyExtenderLabel->setText(message);
    }
}

QString Extender::emptyExtenderMessage() const
{
    return d->emptyExtenderMessage;
}

QList<ExtenderItem*> Extender::items() const
{
    QList<ExtenderItem*> result;

    //FIXME: a triple nested loop ... ew. there should be a more efficient way to do this
    //iterate through all extenders we can find and check each extenders source applet.
    if (!d->applet) {
        return QList<ExtenderItem*>();
    }

    Containment *containment = d->applet.data()->containment();
    if (!containment) {
        return result;
    }

    foreach (Containment *c, containment->corona()->containments()) {
        foreach (Applet *applet, c->applets()) {
            if (applet->d->extender) {
                foreach (ExtenderItem *item, applet->d->extender.data()->d->attachedExtenderItems) {
                    if (item->d->sourceApplet == d->applet.data()) {
                        result.append(item);
                    }
                }
            }
        }
    }

    return result;
}

QList<ExtenderItem*> Extender::attachedItems() const
{
    return d->attachedExtenderItems;
}

QList<ExtenderItem*> Extender::detachedItems() const
{
    QList<ExtenderItem*> result;

    //FIXME: a triple nested loop ... ew. there should be a more efficient way to do this
    //iterate through all extenders we can find and check each extenders source applet.
    if (!d->applet) {
        return QList<ExtenderItem*>();
    }
    Containment *containment = d->applet.data()->containment();
    if (!containment) {
        return result;
    }

    foreach (Containment *c, containment->corona()->containments()) {
        foreach (Applet *applet, c->applets()) {
            if (applet->d->extender) {
                foreach (ExtenderItem *item, applet->d->extender.data()->attachedItems()) {
                    if (item->d->sourceApplet == d->applet.data() && item->isDetached()) {
                        result.append(item);
                    }
                }
            }
        }
    }

    return result;
}

ExtenderItem *Extender::item(const QString &name) const
{
    // chances are the item is in our own extender, so check there first
    foreach (ExtenderItem *item, d->attachedExtenderItems) {
        if (item->d->sourceApplet == d->applet.data() && item->name() == name) {
            return item;
        }
    }

    // maybe it's been moved elsewhere, so lets search through the entire tree of elements
    //FIXME: a triple nested loop ... ew. there should be a more efficient way to do this
    //iterate through all extenders we can find and check each extenders source applet.
    if (!d->applet) {
        return 0;
    }

    Containment *containment = d->applet.data()->containment();
    if (!containment) {
        return 0;
    }

    QList<Containment *> containments;
    if (containment->corona()) {
        containments = containment->corona()->containments();
    } else {
        containments << containment;
    }

    foreach (Containment *c, containments) {
        foreach (Applet *applet, c->applets()) {
            if (applet->d->extender) {
                if (applet->d->extender.data() == this) {
                    // skip it, we checked it already
                    continue;
                }

                if (!applet->d->extender) {
                    continue;
                }

                foreach (ExtenderItem *item, applet->d->extender.data()->attachedItems()) {
                    if (item->d->sourceApplet == d->applet.data() && item->name() == name) {
                        return item;
                    }
                }
            }
        }
    }

    return 0;
}

ExtenderGroup *Extender::group(const QString &name) const
{
    return qobject_cast<ExtenderGroup*>(item(name));
}

bool Extender::hasItem(const QString &name) const
{
    if (item(name)) {
        return true;
    }

    if (!d->applet) {
        return false;
    }

    //if item(name) returns false, that doesn't mean that the item doesn't exist, just that it has
    //not been instantiated yet. check to see if there's mention of this item existing in the
    //plasma config's section DetachedExtenderItems
    Corona *corona = qobject_cast<Corona *>(scene());
    if (!corona) {
        return false;
    }

    KConfigGroup extenderItemGroup(corona->config(), "DetachedExtenderItems");
    foreach (const QString &extenderItemId, extenderItemGroup.groupList()) {
        KConfigGroup cg = extenderItemGroup.group(extenderItemId);
        if (uint(cg.readEntry("sourceAppletId", 0)) == d->applet.data()->id() &&
            cg.readEntry("extenderItemName", "") == name &&
            cg.readEntry("sourceAppletPluginName", "") == d->applet.data()->pluginName()) {
            return true;
        }
    }

    return false;
}

void Extender::setAppearance(Appearance appearance)
{
    if (d->appearance == appearance) {
        return;
    }

    d->appearance = appearance;
    d->updateBorders();
}

Extender::Appearance Extender::appearance() const
{
    return d->appearance;
}

QList<ExtenderGroup*> Extender::groups() const
{
    QList<ExtenderGroup *> result;
    foreach (ExtenderItem *item, d->attachedExtenderItems) {
        if (item->isGroup() && !result.contains(item->group())) {
           ExtenderGroup *group = qobject_cast<ExtenderGroup *>(item);
           if (group) {
               result.append(group);
           }
        }
    }
    return result;
}

Applet *Extender::applet() const
{
    return d->applet.data();
}

void Extender::saveState()
{
    foreach (ExtenderItem *item, attachedItems()) {
        item->config().writeEntry("extenderItemPosition", item->geometry().y());
    }
}

QVariant Extender::itemChange(GraphicsItemChange change, const QVariant &value)
{
    if (change == QGraphicsItem::ItemPositionHasChanged) {
        emit geometryChanged();
    }

    return QGraphicsWidget::itemChange(change, value);
}

void Extender::resizeEvent(QGraphicsSceneResizeEvent *event)
{
    QGraphicsWidget::resizeEvent(event);
    emit geometryChanged();
}

void Extender::mousePressEvent(QGraphicsSceneMouseEvent *event)
{
    Q_UNUSED(event)

    if (!d->applet) {
        return;
    }

    PopupApplet *popupApplet = qobject_cast<PopupApplet*>(d->applet.data());
    if (isEmpty() && popupApplet) {
        popupApplet->hidePopup();
    }
}

void Extender::dragEnterEvent(QGraphicsSceneDragDropEvent *event)
{
    if (event->mimeData()->hasFormat(ExtenderItemMimeData::mimeType())) {
        event->accept();

        const ExtenderItemMimeData *mimeData =
            qobject_cast<const ExtenderItemMimeData*>(event->mimeData());

        if (mimeData) {
            itemHoverEnterEvent(mimeData->extenderItem());

            PopupApplet *popupApplet = qobject_cast<PopupApplet*>(d->applet.data());
            if (popupApplet) {
                popupApplet->showPopup();
            }
        }
    }
}

void Extender::dragMoveEvent(QGraphicsSceneDragDropEvent *event)
{
    if (event->mimeData()->hasFormat(ExtenderItemMimeData::mimeType())) {
        const ExtenderItemMimeData *mimeData =
            qobject_cast<const ExtenderItemMimeData*>(event->mimeData());

        if (mimeData) {
            itemHoverMoveEvent(mimeData->extenderItem(), event->pos());
        }
    }
}

void Extender::dragLeaveEvent(QGraphicsSceneDragDropEvent *event)
{
    if (event->mimeData()->hasFormat(ExtenderItemMimeData::mimeType())) {
        const ExtenderItemMimeData *mimeData =
            qobject_cast<const ExtenderItemMimeData*>(event->mimeData());

        if (mimeData) {
            itemHoverLeaveEvent(mimeData->extenderItem());

            //Some logic to conveniently show/hide popups or applets when logical.
            Extender *sourceExtender = mimeData->extenderItem()->d->extender;

            //Hide popups when they're not the extender where we started, and we're leaving the
            //extender. Use a small timeout here, to avoid accidental hides of extenders we're
            //targetting.
            PopupApplet *popupApplet = qobject_cast<PopupApplet*>(d->applet.data());
            if (popupApplet && sourceExtender != this) {
                kDebug() << "leaving another extender then the extender we started, so hide the popup.";
                popupApplet->showPopup(250);
            }

            //Hide popups when we drag the last item away.
            if (popupApplet && sourceExtender == this && (attachedItems().count() < 2)) {
                kDebug() << "leaving the extender, and there are no more attached items so hide the popup.";
                popupApplet->hidePopup();
            }

            //Hide empty internal extender containers when we drag the last item away. Avoids having
            //an ugly empty applet on the desktop temporarily.
            ExtenderApplet *extenderApplet = qobject_cast<ExtenderApplet*>(d->applet.data());
            if (extenderApplet && sourceExtender == this && attachedItems().count() < 2 &&
                extenderApplet->formFactor() != Plasma::Horizontal &&
                extenderApplet->formFactor() != Plasma::Vertical) {
                kDebug() << "leaving the internal extender container, so hide the applet and it's handle.";
                extenderApplet->hide();
                AppletHandle *handle = dynamic_cast<AppletHandle*>(extenderApplet->parentItem());
                if (handle) {
                    handle->hide();
                }
            }
        }
    }
}

void Extender::dropEvent(QGraphicsSceneDragDropEvent *event)
{
    if (event->mimeData()->hasFormat(ExtenderItemMimeData::mimeType())) {
        const ExtenderItemMimeData *mimeData =
            qobject_cast<const ExtenderItemMimeData*>(event->mimeData());

        if (mimeData) {
            mimeData->extenderItem()->setExtender(this, event->pos());
            QApplication::restoreOverrideCursor();
            itemHoverLeaveEvent(0);
        }
    }
}

void Extender::itemAddedEvent(ExtenderItem *item, const QPointF &pos)
{
    if (!item->group()) {
        if (pos == QPointF(-1, -1)) {
            //if it was already there, reposition
            d->layout->removeItem(item);
            //if just plain adding an item, add it at a sane position:
            if (appearance() == BottomUpStacked) {
                //at the top
                d->layout->insertItem(0, item);
            } else {
                //at the bottom
                d->layout->addItem(item);
            }
        } else {
            kDebug() << "inserting at" << pos << d->insertIndexFromPos(pos) << item->size();
            d->layout->insertItem(d->insertIndexFromPos(pos), item);
            kDebug() << item->size();
        }
    }

    //remove the empty extender message if needed.
    d->updateEmptyExtenderLabel();
    d->updateBorders();
}

void Extender::itemRemovedEvent(ExtenderItem *item)
{
    if (d->destroying) {
        return;
    }

    d->layout->removeItem(item);

    if (d->spacerWidget) {
        d->layout->removeItem(d->spacerWidget);
        delete d->spacerWidget;
        d->spacerWidget = 0;
    }

    //add the empty extender message if needed.
    d->updateEmptyExtenderLabel();
    d->updateBorders();

    updateGeometry();
    resize(effectiveSizeHint(Qt::PreferredSize));
}

void Extender::itemHoverEnterEvent(ExtenderItem *item)
{
    itemHoverMoveEvent(item, QPointF(0, 0));
}

void Extender::itemHoverMoveEvent(ExtenderItem *item, const QPointF &pos)
{
    if (d->spacerWidget && d->spacerWidget->geometry().contains(pos)) {
        return;
    }

    //Make sure we remove any spacer that might already be in the layout.
    if (d->spacerWidget) {
        d->layout->removeItem(d->spacerWidget);
    }

    int insertIndex = d->insertIndexFromPos(pos);

    //Create a widget that functions as spacer, and add that to the layout.
    if (!d->spacerWidget) {
        Spacer *widget = new Spacer(this);
        qreal left, top, right, bottom;
        d->background->getMargins(left, top, right, bottom);
        widget->setMargins(left, 4, right, 4);

        widget->setMinimumSize(item->minimumSize());
        widget->setPreferredSize(item->preferredSize());
        widget->setMaximumSize(item->maximumSize());
        widget->setSizePolicy(item->sizePolicy());
        d->spacerWidget = widget;
    }
    d->layout->insertItem(insertIndex, d->spacerWidget);

    //Make sure we remove any 'no detachables' label that might be there, and update the layout.
    d->updateEmptyExtenderLabel();
}

void Extender::itemHoverLeaveEvent(ExtenderItem *item)
{
    Q_UNUSED(item);

    if (d->spacerWidget) {
        //Remove any trace of the spacer widget.
        d->layout->removeItem(d->spacerWidget);
        delete d->spacerWidget;
        d->spacerWidget = 0;

        d->currentSpacerIndex = -1;

        d->updateEmptyExtenderLabel();
    }
}

FrameSvg::EnabledBorders Extender::enabledBordersForItem(ExtenderItem *item) const
{
    if (d->layout->count() < 1) {
        return 0;
    }

    ExtenderItem *topItem = dynamic_cast<ExtenderItem*>(d->layout->itemAt(0));
    ExtenderItem *bottomItem = dynamic_cast<ExtenderItem*>(d->layout->itemAt(d->layout->count() - 1));
    if (item->group()) {
        return FrameSvg::NoBorder;
    } else if (d->appearance == TopDownStacked && bottomItem != item) {
        return FrameSvg::LeftBorder | FrameSvg::BottomBorder | FrameSvg::RightBorder;
    } else if (d->appearance == BottomUpStacked && topItem != item) {
        return FrameSvg::LeftBorder | FrameSvg::TopBorder | FrameSvg::RightBorder;
    } else if (d->appearance != NoBorders) {
        return FrameSvg::LeftBorder | FrameSvg::RightBorder;
    } else {
        return 0;
    }
}

ExtenderPrivate::ExtenderPrivate(Applet *applet, Extender *extender) :
    q(extender),
    applet(applet),
    background(new FrameSvg(extender)),
    currentSpacerIndex(-1),
    spacerWidget(0),
    emptyExtenderMessage(QString()),
    emptyExtenderLabel(0),
    appearance(Extender::NoBorders),
    destroying(false)
{
    background->setImagePath("widgets/extender-background");
}

ExtenderPrivate::~ExtenderPrivate()
{
}

void ExtenderPrivate::addExtenderItem(ExtenderItem *item, const QPointF &pos)
{
    if (attachedExtenderItems.contains(item)) {
        q->itemAddedEvent(item, pos);
        return;
    }

    QObject::connect(item, SIGNAL(destroyed(ExtenderItem*)), q, SLOT(extenderItemDestroyed(ExtenderItem*)));
    attachedExtenderItems.append(item);
    q->itemHoverLeaveEvent(item);
    pendingItems.append(QPair<ExtenderItem *, QPointF>(item, pos));
    QTimer::singleShot(0, q, SLOT(delayItemAddedEvent()));
}

void ExtenderPrivate::removeExtenderItem(ExtenderItem *item)
{
    attachedExtenderItems.removeAll(item);

    //collapse the popupapplet if the last item is removed.
    if (attachedExtenderItems.isEmpty()) {
        PopupApplet *popupApplet = qobject_cast<PopupApplet*>(applet.data());
        if (popupApplet) {
            popupApplet->hidePopup();
        }
    }

    q->itemRemovedEvent(item);
}

int ExtenderPrivate::insertIndexFromPos(const QPointF &pos) const
{
    int insertIndex = -1;

    //XXX: duplicated from panel
    if (pos != QPointF(-1, -1)) {
        for (int i = 0; i < layout->count(); ++i) {
            QRectF siblingGeometry = layout->itemAt(i)->geometry();
            qreal middle = (siblingGeometry.top() + siblingGeometry.bottom()) / 2.0;
            if (pos.y() < middle) {
                insertIndex = i;
                break;
            } else if (pos.y() <= siblingGeometry.bottom()) {
                insertIndex = i + 1;
                break;
            }
        }
    }

    return insertIndex;
}

void ExtenderPrivate::loadExtenderItems()
{
    if (!applet) {
        return;
    }

    KConfigGroup cg = applet.data()->config("ExtenderItems");

    //first create a list of extenderItems, and then sort them on their position, so the items get
    //recreated in the correct order.
    QList<QPair<int, QString> > groupList;
    foreach (const QString &extenderItemId, cg.groupList()) {
        KConfigGroup dg = cg.group(extenderItemId);
        groupList.append(qMakePair(dg.readEntry("extenderItemPosition", 0), extenderItemId));
    }
    qSort(groupList);

    //iterate over the extender items
    for (int i = 0; i < groupList.count(); i++) {
        QPair<int, QString> pair = groupList[i];

        KConfigGroup dg = cg.group(pair.second);

        //load the relevant settings.
        QString extenderItemId = dg.name();
        QString extenderItemName = dg.readEntry("extenderItemName", "");
        QString appletName = dg.readEntry("sourceAppletPluginName", "");
        uint sourceAppletId = dg.readEntry("sourceAppletId", 0);

        bool temporarySourceApplet = false;

        kDebug() << "applet id = " << applet.data()->id();
        kDebug() << "sourceappletid = " << sourceAppletId;

        //find the source applet.
        Applet *sourceApplet = 0;
        if (applet.data()->id() == sourceAppletId) {
            // it's ours!
            sourceApplet = applet.data();
        } else {
            // maybe it's foreign?
            Containment *containment = applet.data()->containment();

            if (containment) {
                Corona *corona = containment->corona();

                if (sourceAppletId == q->applet()->id()) {
                    sourceApplet = q->applet();
                } else {
                    foreach (Containment *containment, corona->containments()) {
                        foreach (Applet *applet, containment->applets()) {
                            if (applet->id() == sourceAppletId) {
                                sourceApplet = applet;
                            }
                        }
                    }
                }
            }
        }

        //There is no source applet. We just instantiate one just for the sake of creating
        //detachables.
        if (!sourceApplet) {
            kDebug() << "creating a temporary applet as factory";
            sourceApplet = Applet::load(appletName);
            temporarySourceApplet = true;
            //TODO: maybe add an option to applet to indicate that it shouldn't be deleted after
            //having used it as factory.
        }

        if (!sourceApplet) {
            kDebug() << "sourceApplet is null? appletName = " << appletName;
            kDebug() << "                      extenderItemId = " << extenderItemId;
        } else {
            ExtenderItem *item;
            if (dg.readEntry("isGroup", false)) {
                item = new ExtenderGroup(q, extenderItemId.toInt());
            } else {
                item = new ExtenderItem(q, extenderItemId.toInt());
            }
            sourceApplet->initExtenderItem(item);
            item->d->sourceApplet = sourceApplet;

            if (temporarySourceApplet) {
                delete sourceApplet;
            }
        }
    }
}

void ExtenderPrivate::updateBorders()
{
    foreach (ExtenderItem *item, attachedExtenderItems) {
        if (item && (item->d->background->enabledBorders() != q->enabledBordersForItem(item))) {
            //call themeChanged to change the backgrounds enabled borders, and move all contained
            //widgets according to it's changed margins.
            item->d->themeChanged();
        }
    }
}

void ExtenderPrivate::delayItemAddedEvent()
{
    while (!pendingItems.isEmpty()) {
        QPair<Plasma::ExtenderItem *, QPointF> item = pendingItems.first();
        q->itemAddedEvent(item.first, item.second);
        pendingItems.pop_front();
    }
}

void ExtenderPrivate::updateEmptyExtenderLabel()
{
    if (q->isEmpty() && !emptyExtenderLabel &&
        !emptyExtenderMessage.isEmpty() && !spacerWidget ) {
        //add the empty extender label.
        emptyExtenderLabel = new Label(q);
        emptyExtenderLabel->setAlignment(Qt::AlignCenter);
        emptyExtenderLabel->setText(emptyExtenderMessage);

        qreal left, top, right, bottom;
        background->getMargins(left, top, right, bottom);
        emptyExtenderLabel->nativeWidget()->setMargin(left + right);

        emptyExtenderLabel->setSizePolicy(QSizePolicy::MinimumExpanding, QSizePolicy::Fixed);
        layout->addItem(emptyExtenderLabel);
    } else if (!q->isEmpty() && emptyExtenderLabel) {
        //remove the empty extender label.
        layout->removeItem(emptyExtenderLabel);
        delete emptyExtenderLabel;
        emptyExtenderLabel = 0;
    }
}

ExtenderGroup *ExtenderPrivate::findGroup(const QString &name) const
{
    foreach (ExtenderItem *item, attachedExtenderItems) {
        if (item->isGroup() && item->name() == name) {
            return qobject_cast<ExtenderGroup*>(item);
        }
    }

    return 0;
}

void ExtenderPrivate::extenderItemDestroyed(ExtenderItem *item)
{
    if (item && attachedExtenderItems.contains(item)) {
        removeExtenderItem(item);
    }
}

bool Extender::isEmpty() const
{
    //It's empty if it doesn't have items or has only group that are empty and autohide
    foreach (ExtenderItem *item, d->attachedExtenderItems) {
        if (!item->isGroup()) {
            return false;
        } else {
            //a static_cast here should be safe, it's not the case apparently
            ExtenderGroup *group = qobject_cast<ExtenderGroup *>(item);
            if (group && (!group->autoHide() || group->items().size() > 0)) {
                return false;
            }
        }
    }

    return true;
}

} // Plasma namespace

#include "extender.moc"