QGIS/src/gui/attributetable/qgsattributetablemodel.h

/***************************************************************************
  QgsAttributeTableModel.h - Models for attribute table
  -------------------
         date                 : Feb 2009
         copyright            : Vita Cizek
         email                : weetya (at) gmail.com

 ***************************************************************************
 *                                                                         *
 *   This program 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 2 of the License, or     *
 *   (at your option) any later version.                                   *
 *                                                                         *
 ***************************************************************************/

#ifndef QGSATTRIBUTETABLEMODEL_H
#define QGSATTRIBUTETABLEMODEL_H

#include <QAbstractTableModel>
#include <QModelIndex>
#include <QObject>
#include <QHash>
#include <QQueue>
#include <QMap>

#include "qgsvectorlayer.h" // QgsAttributeList
#include "qgsvectorlayercache.h"

class QgsMapCanvas;

/**
 * A model backed by a {@link QgsVectorLayerCache} which is able to provide
 * feature/attribute information to a QAbstractItemView.
 *
 * @brief
 * Is able to generate editor widgets for its QModelIndexes as well.
 * Is mostly referred to as "master model" within this doc and the source.
 *
 * @see <a href="http://doc.qt.digia.com/qt/model-view-programming.html">Qt Model View Programming</a>
 */
class GUI_EXPORT QgsAttributeTableModel: public QAbstractTableModel
{
    Q_OBJECT

  public:
    enum Role
    {
      SortRole = Qt::UserRole + 1,
      FeatureIdRole = Qt::UserRole + 2,
      FieldIndexRole = Qt::UserRole + 3
    };

  public:
    /**
     * Constructor
     * @param layerCache  A layer cache to use as backend
     * @param parent      The parent QObject (owner)
     */
    QgsAttributeTableModel( QgsVectorLayerCache *layerCache, QObject *parent = 0 );

    virtual ~QgsAttributeTableModel();

    /**
     * Loads the layer into the model
     * Preferably to be called, before basing any other models on this model
     */
    virtual void loadLayer();

    /**
     * Returns the number of rows
     * @param parent parent index
     */
    virtual int rowCount( const QModelIndex &parent = QModelIndex() ) const;

    /**
     * Returns the number of columns
     * @param parent parent index
     */
    int columnCount( const QModelIndex &parent = QModelIndex() ) const;

    /**
     * Returns header data
     * @param section required section
     * @param orientation horizontal or vertical orientation
     * @param role data role
     */
    QVariant headerData( int section, Qt::Orientation orientation, int role = Qt::DisplayRole ) const;

    /**
     * Returns data on the given index
     * @param index model index
     * @param role data role
     */
    virtual QVariant data( const QModelIndex &index, int role ) const;

    /**
     * Updates data on given index
     * @param index model index
     * @param value new data value
     * @param role data role
     */
    virtual bool setData( const QModelIndex &index, const QVariant &value, int role = Qt::EditRole );

    /**
     * Returns item flags for the index
     * @param index model index
     */
    Qt::ItemFlags flags( const QModelIndex &index ) const;

    /**
     * Reloads the model data between indices
     * @param index1 start index
     * @param index2 end index
     */
    void reload( const QModelIndex &index1, const QModelIndex &index2 );

    /**
     * Remove rows
     */
    bool removeRows( int row, int count, const QModelIndex &parent = QModelIndex() );

    /**
     * Resets the model
     */
    void resetModel();

    /**
     * Maps feature id to table row
     * @param id feature id
     */
    int idToRow( QgsFeatureId id ) const;

    QModelIndex idToIndex( QgsFeatureId id ) const;

    QModelIndexList idToIndexList( QgsFeatureId id ) const;

    /**
     * get field index from column
     */
    int fieldIdx( int col ) const;

    /**
     * get column from field index
     */
    int fieldCol( int idx ) const;

    /**
     * Maps row to feature id
     * @param row row number
     */
    QgsFeatureId rowToId( int row ) const;

    /**
     * Swaps two rows
     * @param a first row
     * @param b second row
     */
    void swapRows( QgsFeatureId a, QgsFeatureId b );

    /**
     * Returns the layer this model uses as backend. Retrieved from the layer cache.
     */
    inline QgsVectorLayer* layer() const { return mLayerCache ? mLayerCache->layer() : NULL; }

    /**
     * Returns the layer cache this model uses as backend.
     */
    inline QgsVectorLayerCache* layerCache() const { return mLayerCache; }

    /**
     * Execute an action
     */
    void executeAction( int action, const QModelIndex &idx ) const;

    /**
     * Return the feature attributes at given model index
     * @return feature attributes at given model index
     */
    QgsFeature feature( const QModelIndex &idx ) const;

    /**
     * Caches the entire data for one column. This should be called prior to sorting,
     * so the data does not have to be fetched for every single comparison.
     * Specify -1 as column to invalidate the cache
     *
     * @param column The column index of the field to catch
     */
    void prefetchColumnData( int column );

  signals:
    /**
     * Model has been changed
     */
    void modelChanged();

    //! @note not available in python bindings
    void progress( int i, bool &cancel );
    void finished();

  private slots:
    /**
     * Launched whenever the number of fields has changed
     */
    virtual void updatedFields();

  protected slots:
    /**
     * Launched when attribute value has been changed
     * @param fid feature id
     * @param idx attribute index
     * @param value new value
     */
    virtual void attributeValueChanged( QgsFeatureId fid, int idx, const QVariant &value );
    /**
     * Launched when a feature has been deleted
     * @param fid feature id
     */
    virtual void featureDeleted( QgsFeatureId fid );
    /**
     * Launched when a feature has been added
     * @param fid feature id
     * @param inOperation guard insertion with beginInsertRows() / endInsertRows()
     */
    virtual void featureAdded( QgsFeatureId fid, bool inOperation = true );

    /**
     * Launched when layer has been deleted
     */
    virtual void layerDeleted();

  protected:
    QgsVectorLayerCache *mLayerCache;
    int mFieldCount;

    mutable QgsFeature mFeat;

    QgsAttributeList mAttributes;
    QMap< int, const QMap<QString, QVariant> * > mValueMaps;

    QHash<QgsFeatureId, int> mIdRowMap;
    QHash<int, QgsFeatureId> mRowIdMap;

    /**
      * Gets mFieldCount, mAttributes and mValueMaps
      */
    virtual void loadAttributes();

  private:
    /**
     * Load feature fid into local cache (mFeat)
     *
     * @param  fid     feature id
     *
     * @return feature exists
     */
    virtual bool loadFeatureAtId( QgsFeatureId fid ) const;

    QgsFeatureRequest mFeatureRequest;

    /** The currently cached column */
    int mCachedField;
    /** Allows to cache one specific column (used for sorting) */
    QHash<QgsFeatureId, QVariant> mFieldCache;
};


#endif