@param tolerance (level of simplification)

@param onlySelectedFeatures if true, only selected features are considered, else all the features

@param p progress dialog (or 0 if no progress dialog is to be shown)

bool simplify( QgsVectorLayer* layer, const QString& shapefileName, double tolerance,

bool onlySelectedFeatures = false, QProgressDialog* p = 0 );

@param shapefileName path to the output shp

@param onlySelectedFeatures if true, only selected features are considered, else all the features

@param p progress dialog (or 0 if no progress dialog is to be shown)

bool centroids( QgsVectorLayer* layer, const QString& shapefileName,

bool onlySelectedFeatures = false, QProgressDialog* p = 0 );

@param shapefileName path to the output shp

@param onlySelectedFeatures if true, only selected features are considered, else all the features

@param p progress dialog (or 0 if no progress dialog is to be shown)

bool extent( QgsVectorLayer* layer, const QString& shapefileName, bool onlySelectedFeatures = false, QProgressDialog* p = 0 );

/**Create buffers for a vector layer and write it to a new shape file

@param dissolve if true, merge all the buffers to a big multipolygon

@param bufferDistanceField index of the attribute field that contains the buffer distance (or -1 if all features have the same buffer distance)

@param p progress dialog (or 0 if no progress dialog is to be shown)

bool buffer( QgsVectorLayer* layer, const QString& shapefileName, double bufferDistance,

bool onlySelectedFeatures = false, bool dissolve = false, int bufferDistanceField = -1, QProgressDialog* p = 0 );

@param uniqueIdField index of the attribute field that contains the unique convex hull id (or -1 if

all features have the same buffer distance)

@param p progress dialog (or 0 if no progress dialog is to be shown)

bool convexHull( QgsVectorLayer* layer, const QString& shapefileName, bool onlySelectedFeatures = false,

int uniqueIdField = -1, QProgressDialog* p = 0 );

@param uniqueIdField index of the attribute field that contains the unique id to dissolve on (or -1 if

all features should be dissolved together)

@param p progress dialog (or 0 if no progress dialog is to be shown)

bool dissolve( QgsVectorLayer* layer, const QString& shapefileName, bool onlySelectedFeatures = false,

int uniqueIdField = -1, QProgressDialog* p = 0 );

@param shapefileName path to the output shp

@param onlySelectedFeatures if true, only selected features are considered, else all the features

@param p progress dialog (or 0 if no progress dialog is to be shown)

bool intersection( QgsVectorLayer* layerA, QgsVectorLayer* layerB,

const QString& shapefileName, bool onlySelectedFeatures = false,

QProgressDialog* p = 0 );