With fltk's built-in tooltip system, Fl::handle_(), upon receipt of a FL_KEYBOARD event, calls Fl_Tooltip::enter((Fl_Widget*)0); to hide the tooltip. Once in a while, after giving a text input focus, I'm careless with the mouse, moving it away and then back over the input, putting a tooltip over what I'm typing. (And presumably textareas could have that happen as well...) Here's one way that it could be dealt with: