AcLyLayerGroup

acly.h

This class is derived from AcLyLayerFilter and serves as the access to layer group filters. It allows the client to specify and retrieve a set of layer IDs. The filter() method returns true if the object ID of the given layer is contained in the set of layer IDs for the AcLyLayerGroup. 

Specifying the filter criteria is done solely by using addLayerId() and removeLayerId(). AcLyLayerGroup doesn't use a filter expression string, so filterExpression() and filterExpressionTree() return a null pointer, and setFilterExpression() returns Acad::eNotApplicable. 

The recommended way of identifying AcLyLayerGroup filters in a group of layer filters is to query the isIdFilter() method, which returns true for an AcLyLayerGroup.