plasma-workspace/components/containmentlayoutmanager/abstractlayoutmanager.h

/*
 *   Copyright 2019 by Marco Martin <mart@kde.org>
 *
 *   This program is free software; you can redistribute it and/or modify
 *   it under the terms of the GNU Library General Public License as
 *   published by the Free Software Foundation; either version 2, or
 *   (at your option) any later version.
 *
 *   This program 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 Library General Public License for more details
 *
 *   You should have received a copy of the GNU Library General Public
 *   License along with this program; if not, write to the
 *   Free Software Foundation, Inc.,
 *   51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.
 *
 */

#pragma once

#include <QObject>
#include "appletslayout.h"

class ItemContainer;

class AbstractLayoutManager : public QObject
{
    Q_OBJECT

public:
    AbstractLayoutManager(AppletsLayout *layout);
    ~AbstractLayoutManager();

    AppletsLayout *layout() const;

    void setCellSize(const QSizeF &size);
    QSizeF cellSize() const;

    /**
     * A size aligned to the gid that fully contains the given size
     */
    QSizeF cellAlignedContainingSize(const QSizeF &size) const;

    /**
     * Positions the item, does *not* assign the space as taken
     */
    void positionItem(ItemContainer *item);

    /**
     * Positions the item and assigns the space as taken by this item
     */
    void positionItemAndAssign(ItemContainer *item);

    /**
     * Set the space of item's rect as occupied by item.
     * The operation may fail if some space of the item's geometry is already occupied.
     * @returns true if the operation succeeded
     */
    bool assignSpace(ItemContainer *item);

    /**
     * If item is occupying space, set it as available
     */
    void releaseSpace(ItemContainer *item);

// VIRTUALS
    virtual QString serializeLayout() const = 0;

    virtual void parseLayout(const QString &savedLayout) = 0;

    virtual void layoutGeometryChanged(const QRectF &newGeometry, const QRectF &oldGeometry);

    /**
     * true if the item is managed by the grid
     */
    virtual bool itemIsManaged(ItemContainer *item) = 0;

    /**
     * Forget about layout information and relayout all items based solely on their current geometry
     */
    virtual void resetLayout() = 0;

    /**
     * Forget about layout information and relayout all items based on their stored geometry first, and if that fails from their current geometry
     */
    virtual void resetLayoutFromConfig() = 0;

    /**
     * Restores an item geometry from the serialized config
     * parseLayout needs to be called before this
     * @returns true if the item was stored in the config
     * and the restore has been performed.
     * Otherwise, the item is not touched and returns false
     */
    virtual bool restoreItem(ItemContainer *item) = 0;

    /**
     * @returns true if the given rectangle is all free space
     */
    virtual bool isRectAvailable(const QRectF &rect) = 0;

Q_SIGNALS:
    /**
     * Emitted when the layout has been changed and now needs saving
     */
    void layoutNeedsSaving();

protected:
    /**
     * Subclasses implement their assignSpace logic here
     */
    virtual bool assignSpaceImpl(ItemContainer *item) = 0;

    /**
     * Subclasses implement their releasespace logic here
     */
    virtual void releaseSpaceImpl(ItemContainer *item) = 0;

    /**
     * @returns a rectangle big at least as minimumSize, trying to be as near as possible to the current item's geometry, displaced in the direction we asked, forwards or backwards
     * @param rect the rect we want to place an item in
     * @param minimumSize the minimum size we need to make sure is available
     */
    virtual QRectF nextAvailableSpace(ItemContainer *item, const QSizeF &minimumSize, AppletsLayout::PreferredLayoutDirection direction) const = 0;

private:
    QRectF candidateGeometry(ItemContainer *item) const;

    AppletsLayout *m_layout;

    // size in pixels of a crid cell
    QSizeF m_cellSize;
};