Implementation idea 1: the elements of void ShowCharacterScreen(void) would have to be saved in a list of {text, x, y, width, height, tooltip_text} and then void HandleCharacterScreen(void) would have to go over that list, checking if mouse is over that text and displaying a tooltip if so.

Implementation idea 2: a text widget is added to the widgets library and each item gains a tooltip through that.

If anyone has a better idea...