void gtk_text_view_add_child_in_window ( GtkTextView* text_view, GtkWidget* child, GtkTextWindowType which_window, gint xpos, gint ypos )
Adds a child at fixed coordinates in one of the text widget’s windows.
The window must have nonzero size (see gtk_text_view_set_border_window_size()). Note that the child coordinates are given relative to scrolling. When placing a child in #GTK_TEXT_WINDOW_WIDGET, scrolling is irrelevant, the child floats above all scrollable areas. But when placing a child in one of the scrollable windows (border windows or text window) it will move with the scrolling as needed.