The program now uses GTK+ by way of gtkmm 3. I decided to read up on GTK this past Saturday. The use of GTK allows the program to more easily integrate with the GNOME Desktop on Linux. GTK is the primary UI technology in the Linux and UNIX world. GTK does work on Windows and MacOs, though I do not know how well. On Linux and UNIX it is tops. I decided that the best long-term focus for the program is the leading desktop environment for Linux and UNIX. The underlying program logic in terms of RSS feed retrieval remains unchanged.
Although the UI source code was reduced substantially, gtkmm 3 is not a breeze to use compared to other UI platforms. There are issues with scroll areas, aesthetic control, and object lifetime management. However, with the right experience, such issues can be worked around. As a result, the gtkmm API is usable. The latest UI source code update is on github.