This function provides a dialogue for selecting one of the items in STR. The amount of items is given by cnt. sx specifies the width of the dialogue window, cpt is the caption. If the user selected an entry, the entry index is returned. If the dialogue is cancelled by touching an area outside the dialogue window, the function returns -1.
lines specifies whether the procedure should draw lines between the strings. The lowest bit decides whether there is a line between entry 1 and 2, the next one for entry 2 and 3 and so on.