Sets the area of the widget, where the contents of this tooltip apply,
to be @rect (in widget coordinates). This is especially useful for
properly setting tooltips on #GtkTreeView rows and cells, #GtkIconViews,
etc.
For setting tooltips on #GtkTreeView, please refer to the convenience
functions for this: gtk_tree_view_set_tooltip_row() and
gtk_tree_view_set_tooltip_cell().
Sets the area of the widget, where the contents of this tooltip apply, to be @rect (in widget coordinates). This is especially useful for properly setting tooltips on #GtkTreeView rows and cells, #GtkIconViews, etc.
For setting tooltips on #GtkTreeView, please refer to the convenience functions for this: gtk_tree_view_set_tooltip_row() and gtk_tree_view_set_tooltip_cell().