DM_SETDROPDOWNOPENED

The ID of the element for which the combo box (DI_COMBOBOX) or history list (DI_EDIT or DI_FIXEDIT with the DIF_HISTORY flag) should be opened.

TRUE - open the list for the element with the given ID.
FALSE - close the open combo box or history list. In this case Param1 is ignored.

If Param2=FALSE the returned value is always TRUE.
If Param2=TRUE, the returned value is TRUE if the combo box or history list has been opened successfully. FALSE is returned if ID of not suppored type was set.

Control	Description
DI_COMBOBOX	combined list
DI_EDIT	edit line
DI_FIXEDIT	fixed-size input field

Only one combo box or history list can be open in a dialog at the same time. Therefore, sending this message with Param2=TRUE closes an already opened combo box before opening the specified one, and when sending the message with Param2=FALSE it is not needed to specify the item ID.