DeclarativeDragArea.h

/*
    SPDX-FileCopyrightText: 2010 BetterInbox <contact@betterinbox.com>
    SPDX-FileContributor: Gregory Schlomoff <greg@betterinbox.com>
 
    SPDX-License-Identifier: MIT
*/
 
#ifndef DECLARATIVEDRAGAREA_H
#define DECLARATIVEDRAGAREA_H
 
#include "DeclarativeMimeData.h"
 
#include <QImage>
#include <QQuickItem>
#include <QSharedPointer>
 
class QQmlComponent;
class QQuickItemGrabResult;
 
class DeclarativeDragArea : public QQuickItem
{
    Q_OBJECT
 
    /**
     * The delegate is the item that will be displayed next to the mouse cursor during the drag and drop operation.
     * It usually consists of a large, semi-transparent icon representing the data being dragged.
     */
    Q_PROPERTY(QQuickItem *delegate READ delegate WRITE setDelegate NOTIFY delegateChanged RESET resetDelegate)
 
    /**
     * The QML element that is the source of the resulting drag and drop operation. This can be defined to any item, and will
     * be available to the DropArea as event.data.source
     */
    Q_PROPERTY(QQuickItem *source READ source WRITE setSource NOTIFY sourceChanged RESET resetSource)
 
    // TODO: to be implemented
    Q_PROPERTY(QQuickItem *target READ source NOTIFY targetChanged)
 
    /**
     * the mime data of the drag operation
     * @see DeclarativeMimeData
     */
    Q_PROPERTY(DeclarativeMimeData *mimeData READ mimeData CONSTANT)
 
    /**
     * If false no drag operation will be generate
     */
    Q_PROPERTY(bool enabled READ isEnabled WRITE setEnabled NOTIFY enabledChanged) // TODO: Should call setAcceptDrops()
 
    /**
     * Supported operations, a combination of
     *  Qt.CopyAction
     *  Qt.MoveAction
     *  Qt.LinkAction
     *  Qt.ActionMask
     *  Qt.IgnoreAction
     *  Qt.TargetMoveAction
     */
    Q_PROPERTY(Qt::DropActions supportedActions READ supportedActions WRITE setSupportedActions NOTIFY supportedActionsChanged)
 
    /**
     * The default action will be performed during a drag when no modificators are pressed.
     */
    Q_PROPERTY(Qt::DropAction defaultAction READ defaultAction WRITE setDefaultAction NOTIFY defaultActionChanged)
 
    /**
     * distance in pixel after which a drag event will get started
     */
    Q_PROPERTY(int startDragDistance READ startDragDistance WRITE setStartDragDistance NOTIFY startDragDistanceChanged)
 
    /**
     * an image to be used as delegate. if present overrides the delegate property. in can be either a QImage or a QIcon
     */
    Q_PROPERTY(QVariant delegateImage READ delegateImage WRITE setDelegateImage NOTIFY delegateImageChanged)
 
    /**
     * Whether a drag currently originates from this drag area.
     *
     * @since 5.19
     */
    Q_PROPERTY(bool dragActive READ dragActive NOTIFY dragActiveChanged)
 
public:
    DeclarativeDragArea(QQuickItem *parent = nullptr);
    ~DeclarativeDragArea() override;
 
    QQuickItem *delegate() const;
    void setDelegate(QQuickItem *delegate);
    void resetDelegate();
 
    QVariant delegateImage() const;
    void setDelegateImage(const QVariant &image);
    QQuickItem *target() const;
    QQuickItem *source() const;
    void setSource(QQuickItem *source);
    void resetSource();
 
    bool dragActive() const;
 
    bool isEnabled() const;
    void setEnabled(bool enabled);
 
    int startDragDistance() const;
    void setStartDragDistance(int distance);
 
    // supported actions
    Qt::DropActions supportedActions() const;
    void setSupportedActions(Qt::DropActions actions);
 
    // default action
    Qt::DropAction defaultAction() const;
    void setDefaultAction(Qt::DropAction action);
 
    DeclarativeMimeData *mimeData() const;
 
Q_SIGNALS:
    void dragStarted();
    void delegateChanged();
    void dragActiveChanged();
    void sourceChanged();
    void targetChanged();
    void dataChanged();
    void enabledChanged();
    void drop(int action);
    void supportedActionsChanged();
    void defaultActionChanged();
    void startDragDistanceChanged();
    void delegateImageChanged();
 
protected:
    void mouseMoveEvent(QMouseEvent *event) override;
    void mousePressEvent(QMouseEvent *event) override;
    void mouseReleaseEvent(QMouseEvent *) override;
    void timerEvent(QTimerEvent *event) override;
    bool childMouseEventFilter(QQuickItem *item, QEvent *event) override;
 
private:
    void startDrag(const QImage &image);
 
    QQuickItem *m_delegate;
    QQuickItem *m_source;
    QQuickItem *m_target;
    QSharedPointer<QQuickItemGrabResult> m_grabResult;
    bool m_enabled;
    bool m_draggingJustStarted;
    bool m_dragActive;
    Qt::DropActions m_supportedActions;
    Qt::DropAction m_defaultAction;
    DeclarativeMimeData *const m_data;
    QImage m_delegateImage;
    int m_startDragDistance;
    QPointF m_buttonDownPos;
    int m_pressAndHoldTimerId;
};
 
#endif // DECLARATIVEDRAGAREA_H