Filter class should be compiled separately from pcl_ros_filters library

[hershwg]

Documentation about the pcl_ros::Filter class http://ros.org/doc/groovy/api/pcl_ros/html/classpcl__ros_1_1Filter.html makes it appear that it is a class which can be used by implementers of new pcl filter nodelets.

However as pointed out in #9 the CMakeLists.txt file includes the line "class_loader_hide_library_symbols(pcl_ros_filters)", and pcl_ros_filters is the only library containing the compiled contents of pcl_ros::Filter. Therefore pcl_ros::Filter is not actually usable by outside programmers. If it is really intended to be only an internal helper class for the pcl_ros_filters library, then it should be documented as such.

However it appears to be a more generally useful helper class, making it easy to write PCL filter nodelets without a bunch of boilerplate. To make this possible, a new library should be defined, say pcl_ros_filter or pcl_ros_filter_base which contains only pcl_ros::Filter. That library would naturally not have class_loader_hide_library_symbols() because it would not be defining a plugin. Then implementors of new filters would link against that library, as would the existing pcl_ros_filters library.

In the meantime the solution to my problem is to copy pcl_ros/filters/filter.cpp into my own code and do a bunch of renaming.

[tfoote]

Yes, the cleaner solution would be to make it a separate object such that it is reuseable.

[LucidOne]

pull requests are welcome