qt-creator/src/libs/advanceddockingsystem/floatingdragpreview.h

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** Copyright (C) 2020 Uwe Kindler
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#pragma once

#include "floatingdockcontainer.h"

#include <QWidget>

namespace ADS {

class DockWidget;
class DockAreaWidget;
struct FloatingDragPreviewPrivate;

/**
 * A floating overlay is a temporary floating widget that is just used to
 * indicate the floating widget movement.
 * This widget is used as a placeholder for drag operations for non-opaque
 * docking
 */
class FloatingDragPreview : public QWidget, public AbstractFloatingWidget
{
    Q_OBJECT
private:
    FloatingDragPreviewPrivate *d;
    friend struct FloatingDragPreviewPrivate;

    /**
     * Cancel non opaque undocking if application becomes inactive
     */
    void onApplicationStateChanged(Qt::ApplicationState state);

protected:
    /**
     * Updates the drop overlays
     */
    virtual void moveEvent(QMoveEvent *event) override;

    /**
     * Cares about painting the
     */
    virtual void paintEvent(QPaintEvent *event) override;

    /**
     * The content is a DockArea or a DockWidget
     */
    FloatingDragPreview(QWidget *content, QWidget *parent);

public:
    using Super = QWidget;

    /**
     * Creates an instance for undocking the DockWidget in Content parameter
     */
    FloatingDragPreview(DockWidget *content);

    /**
     * Creates an instance for undocking the DockArea given in Content
     * parameters
     */
    FloatingDragPreview(DockAreaWidget *content);

    /**
     * Delete private data
     */
    ~FloatingDragPreview() override;

    /**
     * We filter the events of the assigned content widget to receive
     * escape key presses for canceling the drag operation
     */
    virtual bool eventFilter(QObject *watched, QEvent *event) override;

public: // implements AbstractFloatingWidget
    virtual void startFloating(const QPoint &dragStartMousePos,
                               const QSize &size,
                               eDragState dragState,
                               QWidget *mouseEventHandler) override;

    /**
     * Moves the widget to a new position relative to the position given when
     * startFloating() was called
     */
    virtual void moveFloating() override;

    /**
     * Finishes dragging.
     * Hides the dock overlays and executes the real undocking and docking
     * of the assigned Content widget
     */
    virtual void finishDragging() override;

signals:
    /**
     * This signal is emitted, if dragging has been canceled by escape key
     * or by active application switching via task manager
     */
    void draggingCanceled();
}; // class FloatingDragPreview

} // namespace ADS