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/* === This file is part of Calamares - <https://github.com/calamares> ===
*
* Copyright 2019, Adriaan de Groot <groot@kde.org>
*
* Calamares is free software: you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation, either version 3 of the License, or
* (at your option) any later version.
*
* Calamares 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 General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with Calamares. If not, see <http://www.gnu.org/licenses/>.
*/
#ifndef VARIANTMODEL_H
#define VARIANTMODEL_H
#include <QAbstractItemModel>
#include <QVariantMap>
#include <QVector>
/** @brief A model that operates directly on a QVariant
*
* A VariantModel operates directly on an underlying
* QVariant, treating QVariantMap and QVariantList as
* nodes with multiple children. In general, putting
* a QVariantMap into a QVariant and passing that into
* the model will get you a tree-like model of the
* VariantMap's data structure.
*
* Take care of object lifetimes and that the underlying
* QVariant does not change during use. If the QVariant
* **does** change, call reload() to re-build the internal
* representation of the tree.
*/
class VariantModel : public QAbstractItemModel
{
public:
/** @brief Auxiliary data
*
* The nodes of the tree are enumerated into a vector
* (of length equal to the number of nodes in the tree + 1)
* which are used to do index and parent calculations.
*/
using IndexVector = QVector< quintptr >;
/** @brief Constructor
*
* The QVariant's lifetime is **not** affected by the model,
* so take care that the QVariant lives at least as long as
* the model). Also, don't change the QVariant underneath the model.
*/
VariantModel( const QVariant* p );
~VariantModel() override;
/** @brief Re-build the internal tree
*
* Call this when the underlying variant is changed, which
* might impact how the tree is laid out.
*/
void reload();
int columnCount( const QModelIndex& index ) const override;
int rowCount( const QModelIndex& index ) const override;
QModelIndex index( int row, int column, const QModelIndex& parent ) const override;
QModelIndex parent( const QModelIndex& index ) const override;
QVariant data( const QModelIndex& index, int role ) const override;
QVariant headerData( int section, Qt::Orientation orientation, int role ) const override;
private:
const QVariant* const m_p;
/** @brief Tree representation of the variant.
*
* At index 0 in the vector , we store -1 to indicate the root.
*
* Then we enumerate all the elements in the tree (by traversing
* the variant and using QVariantMap and QVariantList as having
* children, and everything else being a leaf node) and at the index
* for a child, store the index of its parent. This means that direct
* children of the root store a 0 in their indexes, children of the first
* child of the root store a 1, and we can "pointer chase" from an index
* through parents back to index 0.
*
* Because of this structure, the value stored at index i must be
* less than i (except for index 0, which is special). This makes it
* slightly easier to search for a given value *p*, because we can start
* at index *p* (or even *p+1*).
*
* Given an index *i* into the vector corresponding to a child, we know the
* parent, but can also count which row this child should have, by counting
* *other* indexes before *i* with the same parent (and by the ordering
* of values, we can start counting at index *parent-index*).
*
*/
IndexVector m_rows;
/// @brief Implementation of walking an index through the variant-tree
const QVariant underlying( const QModelIndex& index ) const;
/// @brief Helpers for range-checking
inline bool inRange( quintptr p ) const { return p < static_cast< quintptr >( m_rows.count() ); }
inline bool inRange( const QModelIndex& index ) const { return inRange( index.internalId() ); }
};
#endif
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