OpenCPN is a free software (GPLv2) project to create a concise chart
plotter and navigation software, for use underway or as a planning
tool. OpenCPN is developed by a team of active sailors using real
world conditions for program testing and refinement.

wxGTK3 is a required dependency, however you can use wxGTK or
wxPython instead if you prefer.  If decide to use wxGTK you will
have to recompile wxGTK with the --enable-graphics_ctx option
because it is not enabled in the default slackbuild and is
required by opencpn.  The --enable-graphics_ctx option is enabled
by default in the wxGTK3 and wxPython slackbuilds.