plasma-framework/extender.h

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/*
* Copyright 2008 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
*/
#ifndef PLASMA_EXTENDER_H
#define PLASMA_EXTENDER_H
#include <QtGui/QGraphicsWidget>
#include "plasma/plasma_export.h"
namespace Plasma
{
class ExtenderPrivate;
class ExtenderItem;
class Applet;
/**
* @class Extender plasma/extender.h <Plasma/Extender>
*
* @short Extends applets to allow detachable parts
*
* An Extender is a widget that visually extends the normal contents of an applet with
* additional dynamic widgets called ExtenderItems. These ExtenderItems can be
* detached by the user and dropped either on another Extender or on the canvas directly.
*
* This widget allows using ExtenderItems in your applet. Extender takes care of the presentation
* of a collection of ExtenderItems and keeps track of ExtenderItems that originate in it.
*
* The default Extender implementation displays extender items in a vertical layout with
* spacers that appear when dropping an ExtenderItem over it.
*
* If you wish to have a different presentation of extender items, you can choose to subclass
* Extender and reimplement the extenderItem* events and, optionally, the saveState function.
*/
class PLASMA_EXPORT Extender : public QGraphicsWidget
{
Q_OBJECT
Q_PROPERTY(QString emptyExtenderMessage READ emptyExtenderMessage
WRITE setEmptyExtenderMessage)
public:
/**
* Creates an extender. Note that extender expects applet to have a config(), and needs a
* scene because of that. So you should only instantiate an extender in init() or later, not
* in an applet's constructor.
* @param applet The applet this extender is part of. Null is not allowed here.
*/
explicit Extender(Applet *applet);
~Extender();
/**
* @param emptyExtenderMessage The text to be shown whenever the applet's extender is empty.
* Defaults to i18n'ed "no items".
*/
void setEmptyExtenderMessage(const QString &message);
/**
* @return The text to be shown whenever the applet's layout is empty.
*/
QString emptyExtenderMessage() const;
/**
* @returns a list of all extender items (attached AND detached) where the source applet is
* this applet.
*/
QList<ExtenderItem*> items() const;
/**
* @returns a list of all attached extender items.
*/
QList<ExtenderItem*> attachedItems() const;
/**
* @returns a list of all detached extender items.
*/
QList<ExtenderItem*> detachedItems() const;
/**
* This function can be used for easily determining if a certain item is allready displayed
* in a extender item somewhere, so your applet doesn't duplicate this item. Say the applet
* displays 'jobs', from an engine which add's a source for every job. In sourceAdded you
* could do something like:
* if (!item(source)) {
* //add an extender item monitoring this source.
* }
*/
ExtenderItem *item(const QString &name) const;
protected:
/**
* Get's called after an item has been added to this extender. The bookkeeping has allready
* been done when this function get's called. The only thing left to do is put it somewhere
* appropriate. The default implementation adds the extenderItem to the appropriate place in
* a QGraphicsLinearLayout.
* @param item The item that has just been added.
* @param pos The location the item has been dropped in local coordinates.
*/
virtual void itemAddedEvent(ExtenderItem *item, const QPointF &pos);
/**
* Get's called after an item has been removed from this extender. All bookkeeping has
* allready been done when this function get's called.
* @param item The item that has just been removed.
*/
virtual void itemRemovedEvent(ExtenderItem *item);
/**
* Get's called when an ExtenderItem that get's dragged enters this extender. Default
* implementation does nothing.
*/
virtual void itemHoverEnterEvent(ExtenderItem *item);
/**
* Gets called when an ExtenderItem is hovering over this extender. Implement this function
* to give some visual feedback about what will happen when the mouse button is released at
* that position. The default implementation shows a spacer at the appropriate location in
* the layout.
* @param item The item that's hovering over this extender. Most usefull for obtaining the
* size of the spacer.
* @param pos The location the item is hovering.
*/
virtual void itemHoverMoveEvent(ExtenderItem *item, const QPointF &pos);
/**
* Get's called when an ExtenderItem that was previously hovering over this extender moves
* away from this extender. The default implementation removes any spacer from the layout.
*/
virtual void itemHoverLeaveEvent(ExtenderItem *item);
/**
* This function get's called for every extender when plasma exits. Implement this function
* to store the current state of this extender (position in a layout for example), so this
* can be restored when applet starts again. The default implementation stores the y
* coordinate of every extender item in the config field extenderItemPos.
*/
virtual void saveState();
/**
* @reimplemented from QGraphicsWidget
*/
QVariant itemChange(GraphicsItemChange change, const QVariant &value);
/**
* @reimplemented from QGraphicsWidget
*/
void resizeEvent(QGraphicsSceneResizeEvent *event);
Q_SIGNALS:
/**
* Fires when an extender item is added to this extender.
*/
void itemAttached(Plasma::ExtenderItem *);
/**
* Fires when an extender item is removed from this extender.
*/
void itemDetached(Plasma::ExtenderItem *);
/**
* Fires when an extender's preferred size changes.
*/
void geometryChanged();
private:
ExtenderPrivate* const d;
friend class ExtenderPrivate;
friend class ExtenderItem;
friend class ExtenderItemPrivate;
//applet should be able to call saveState();
friend class Applet;
};
} // Plasma namespace
#endif //PLASMA_EXTENDER_H