Custom tooltip will not be displayed (or will blink) near to bottom edge of the desktop.
Steps to reproduce
Tooltip that was created using Gtk.Tooltip.set_custom function (custom_widget) and attached to Treeview.
Current behavior
TreeView tooltip that was created using Gtk.Tooltip.set_custom function (custom_widget) will not be displayed (or will blink) if the tooltip's window is near to bottom edge of the desktop.
Expected outcome
Version information
gtk3.x86_64 3.24.8 Linux - Fedora 30
Additional information
Video and Python example code attached.hello.py