QGIS/python/core/qgsproject.sip

/** Reads and writes project states.
   

  @note

  Has two general kinds of state to make persistent.  (I.e., to read and
  write.)  First, Qgis proprietary information.  Second plug-in information.

  A singleton since there shall only be one active project at a time; and
  provides canonical location for plug-ins and main app to find/set
  properties.

  Might want to consider moving from Singleton; i.e., allowing more than one
  project.  Just as the GIMP can have simultaneous multiple images, perhaps
  qgis can one day have simultaneous multiple projects.

*/
class QgsProject : QObject
{
%TypeHeaderCode
#include <qgsproject.h>
%End

public:

    /**
       @todo XXX Should have semantics for saving project if dirty as last gasp?
    */
    ~QgsProject();

    /// access to canonical QgsProject instance
    static QgsProject * instance();

    /**
       Every project has an associated title string

       @todo However current dialogs don't allow setting of it yet
     */
    //@{
    void title( const QString & title );

    /** returns title */
    const QString & title() const;
    //@}

    /**
       the dirty flag is true if the project has been modified since the last
       write()
     */
    //@{
    bool isDirty() const;

    void dirty( bool b );
    //@}


    /**
       Every project has an associated file that contains its XML
     */
    //@{
    void setFileName( const QString & name );

    /** returns file name */
    QString fileName() const;
    //@}


    /** read project file

       @note Any current plug-in state is erased

       @note dirty set to false after successful invocation

       @note file name argument implicitly sets file

       (Is that really desirable behavior?  Maybe prompt to save before
       reading new one?)

       Should we presume the file is opened elsewhere?  Or do we open it
       ourselves?

       XXX How to best get modify access to Qgis state?  Actually we can finagle
       that by searching for qgisapp in object hiearchy.

       @note

       - Gets the extents
       - Creates maplayers
       - Registers maplayers

       @note it's presumed that the caller has already reset the map canvas, map registry, and legend

       @exception

     */
    //@{
    bool read( const QFileInfo & file );
    bool read( );
    //@}


    /** read the layer described in the associated Dom node

        @param layerNode   represents a QgsProject Dom node that maps to a specific layer.

        QgsProject raises an exception when one of the QgsProject::read()
        implementations fails.  Since the read()s are invoked from qgisapp,
        then qgisapp handles the exception.  It prompts the user for the new
        location of the data, if any.  If there is a new location, the Dom
        node associated with the layer has its <datasource> tag corrected.
        Then that node is passed to this member function to be re-opened.

     */
    bool read( QDomNode & layerNode );


    /** write project file

       XXX How to best get read access to Qgis state?  Actually we can finagle
       that by searching for qgisapp in object hiearchy.

       @note file name argument implicitly sets file

       @note dirty set to false after successful invocation
     */
    //@{
    bool write( const QFileInfo & file );
    bool write( );
    //@}


    /// syntactic sugar for property lists
    // DEPRECATED typedef QPair< QString, QVariant >  PropertyValue;
    // DEPRECATED typedef QValueList< PropertyValue > Properties;

    /** extra properties, typically added by plug-ins

       This allows for extra properties to be associated with projects.  Think
       of it as a registry bound to a project.

       Properties are arbitrary values keyed by a name and associated with a
       scope.  The scope would presumably refer to your plug-in.
       E.g., "openmodeller".

       @note

       E.g., open modeller might use:

       <code>"QgsProject::instance()->properties("openmodeller")["foo"]</code>.

       @todo "properties" is, overall, a good name; but that might imply that
       the qgis specific state properites are different since they aren't
       accessible here.  Actually, what if we make "qgis" yet another
       scope that stores its state in the properties list?  E.g., 
       QgsProject::instance()->properties()["qgis"]?

       
     */
    // DEPRECATED Properties & properties( QString const & scope );

    /**
       removes all project properties
    */
    void clearProperties();


    /* key value mutators 

      keys would be the familiar QSettings-like '/' delimited entries, implying
      a hierarchy of keys and corresponding values

      @note The key string <em>must</em> include '/'s.  E.g., "/foo" not "foo".
    */
    //@{
    // TODO: resolve somehow to use always correct function
    //bool writeEntry ( const QString & scope, const QString & key, bool value );
    //bool writeEntry ( const QString & scope, const QString & key, double value );
    bool writeEntry ( const QString & scope, const QString & key, int value );
    bool writeEntry ( const QString & scope, const QString & key, const QString & value );
    bool writeEntry ( const QString & scope, const QString & key, const QStringList & value );
    //@}

    /** key value accessors

        keys would be the familiar QSettings-like '/' delimited entries,
        implying a hierarchy of keys and corresponding values


        @note The key string <em>must</em> include '/'s.  E.g., "/foo" not "foo".
    */
    //@{
    QStringList readListEntry ( const QString & scope, const QString & key, bool * ok = 0 ) const;

    QString readEntry ( const QString & scope, const QString & key, const QString & def = QString::null, bool * ok = 0 ) const;
    int readNumEntry ( const QString & scope, const QString & key, int def = 0, bool * ok = 0 ) const;
    double readDoubleEntry ( const QString & scope, const QString & key, double def = 0, bool * ok = 0 ) const;
    bool readBoolEntry ( const QString & scope, const QString & key, bool def = FALSE, bool * ok = 0 ) const;
    //@}


    /** remove the given key */
    bool removeEntry ( const QString & scope, const QString & key );


    /** return keys with values -- do not return keys that contain other keys

      @note equivalent to QSettings entryList()
    */
    QStringList entryList ( const QString & scope, const QString & key ) const;

    /** return keys with keys -- do not return keys that contain only values

      @note equivalent to QSettings subkeyList()
    */
    QStringList subkeyList ( const QString & scope, const QString & key ) const;


    /** dump out current project properties to stderr 

      @todo XXX Now slightly broken since re-factoring.  Won't print out top-level key
                and redundantly prints sub-keys.
    */
    void dumpProperties() const;

    /** prepare a filename to save it to the project file
      @note added in 1.3 */
    QString writePath( QString filename ) const;

    /** turn filename read from the project file to an absolute path
      @note added in 1.3 */
    QString readPath( QString filename ) const;

    /** Return error message from previous read/write
      @note added in 1.4 */
    QString error() const;

    /** Change handler for missing layers.
      Deletes old handler and takes ownership of the new one.
      @note added in 1.4 */
    void setBadLayerHandler( QgsProjectBadLayerHandler* handler );

  protected:

    /** Set error message from read/write operation
      @note added in 1.4 */
    void setError( QString errorMessage );

    /** Clear error message
      @note added in 1.4 */
    void clearError();

  signals:
    
    //! emitted when project is being read
    void readProject(const QDomDocument &);
    
    //! emitted when project is being written
    void writeProject(QDomDocument &);

  private:

    QgsProject(); // private 'cause it's a singleton

}; // QgsProject


/** Interface for classes that handle missing layer files when reading project file.
  @note added in 1.4 */
class QgsProjectBadLayerHandler
{
%TypeHeaderCode
#include <qgsproject.h>
%End

public:
  virtual void handleBadLayers( QList<QDomNode> layers, QDomDocument projectDom ) = 0;
  virtual ~QgsProjectBadLayerHandler();
};


/** Default bad layer handler which ignores any missing layers.
  @note added in 1.4 */
class QgsProjectBadLayerDefaultHandler : QgsProjectBadLayerHandler
{
%TypeHeaderCode
#include <qgsproject.h>
%End

public:
  virtual void handleBadLayers( QList<QDomNode> layers, QDomDocument projectDom );

};