It would be good to have a popup menu check box to wrap lines.
There is a [wrap](https://docs.gtk.org/gtk3/property.CellRendererText.wrap-mode.html) property to render treeview lines, but I can't get that to work. Here's my branch: https://github.com/ntrel/geany/commits/msgwin-wrap/
Even if you call `g_object_set` when the cell renderer is created, it still doesn't work because of a GTK bug: https://stackoverflow.com/questions/17597043/gtk-cellrenderertext-makes-itse...
It was closed as won't fix: https://gitlab.gnome.org/GNOME/gtk/-/issues/12