The pictures in the overlay list come from the regular picture list. First you must add pictures to the regular list, either in the painter or during execution. Then during execution you specify pictures for the overlay picture list. After that you can assign an overlay picture to items, individually or with the SetLevelPictures function.
This code adds a picture to the regular picture list and then assigns it to the overlay list:
integer idx
idx = tv_1.AddPicture("Custom085!")
IF tv_1.SetOverlayPicture(1, idx) <> 1 THEN
sle_get.Text = "Setting overlay picture failed"
END IF
This code for the Clicked event turns the overlay picture on or off each time the user clicks an item:
treeviewitem tvi
This.GetItem(handle, tvi)
IF tvi.OverlayPictureIndex = 0 THEN
tvi.OverlayPictureIndex = 1
ELSE
tvi.OverlayPictureIndex = 0
END IF
This.SetItem(handle, tvi)
