The Dialog structure contains functions and structures to create and operate on dialogue boxes.

structure Dialog:
    type HWND and HINSTANCE 
          DLG_CLASS of string * Window.Style.flags
        | DLG_BUTTON of Button.Style.flags
        | DLG_COMBOBOX of Combobox.Style.flags
        | DLG_EDIT of Edit.Style.flags
        | DLG_LISTBOX of Listbox.Style.flags
        | DLG_SCROLLBAR of Scrollbar.Style.flags
        | DLG_STATIC of Static.Style.flags

    datatype DLGTITLE = DLG_TITLERESOURCE of int | DLG_TITLESTRING of string
    structure Style:
        include BIT_FLAGS
        val WS_OVERLAPPED: flags and WS_POPUP: flags and WS_CHILD: flags and WS_MINIMIZE: flags
        and WS_VISIBLE: flags and WS_DISABLED:flags and WS_CLIPSIBLINGS:flags
        and WS_CLIPCHILDREN:flags and WS_MAXIMIZE:flags and WS_CAPTION:flags
        and WS_BORDER:flags and WS_DLGFRAME:flags and WS_VSCROLL:flags and WS_HSCROLL:flags
        and WS_SYSMENU:flags and WS_THICKFRAME:flags and WS_GROUP:flags and WS_TABSTOP:flags
        and WS_MINIMIZEBOX:flags and WS_MAXIMIZEBOX:flags and WS_TILED:flags and WS_ICONIC:flags
        and WS_SIZEBOX:flags and WS_OVERLAPPEDWINDOW:flags and WS_TILEDWINDOW:flags
        and WS_POPUPWINDOW:flags and WS_CHILDWINDOW:flags
        and DS_3DLOOK: flags and DS_ABSALIGN: flags and DS_CENTER: flags and DS_CENTERMOUSE: flags
        and DS_CONTEXTHELP: flags and DS_CONTROL: flags and DS_FIXEDSYS: flags
        and DS_LOCALEDIT: flags and DS_MODALFRAME: flags and DS_NOFAILCREATE: flags
        and DS_NOIDLEMSG: flags and DS_SETFONT: flags and DS_SETFOREGROUND: flags
        and DS_SYSMODAL: flags

        { extendedStyle: int,
          x: int,
          y: int,
          cx : int,
          cy: int,
          id: int,
          class: DLGCLASSES,
          title: DLGTITLE,
          creationData: Word8Vector.vector option
    type DLGTEMPLATE =
        { style: Style.flags,
          extendedStyle: int,
          x : int,
          y: int,
          cx: int,
          cy: int,
          menu: Resource.RESID option,
          class: Resource.RESID option,
          title: string,
          font: (int * string) option,
          items: DLGITEMTEMPLATE list

    val DialogBox :
        HINSTANCE * Resource.RESID * HWND *
        (HWND * Message.Message * 'a -> Message.LRESULT * 'a) * 'a -> int
    val DialogBoxIndirect: HINSTANCE * DLGTEMPLATE * HWND *
        (HWND * Message.Message * 'a -> Message.LRESULT * 'a) * 'a -> int
    val CreateDialog : HINSTANCE * Resource.RESID * HWND *
        (HWND * Message.Message * 'a -> Message.LRESULT * 'a) * 'a -> HWND
    val CreateDialogIndirect: HINSTANCE * DLGTEMPLATE * HWND *
        (HWND * Message.Message * 'a -> Message.LRESULT * 'a) * 'a -> HWND

    val GetDialogBaseUnits : unit -> {horizontal: int, vertical: int}
    val GetDlgCtrlID: HWND -> int
    and GetDlgItem: HWND * int -> HWND
    and GetDlgItemText: HWND * int -> string
    and IsDialogMessage: HWND * Message.MSG -> bool
    and EndDialog: HWND * int -> unit

    val compileTemplate : DLGTEMPLATE -> Word8Vector.vector
    val decompileTemplate : Word8Vector.vector -> DLGTEMPLATE

DialogBox(hInst, resId, parent, dlgProc, dlgInit)
DialogBoxIndirect(hInst, template, parent, dlgProc, dlgInit)
CreateDialog(hInst, resId, parent, dlgProc, dlgInit)
CreateDialogIndirect(hInst, template, parent, dlgProc, dlgInit)

These four functions all create dialogues.  They all take a dialogue procedure and an initial state for the dialogue.  A dialogue procedure has the form
dlgProc(dlg, msg, state) and returns a pair consisting of the result of processing the message (LRESINT 0 if the message is not processed) and a new state.  Each time the dialogue procedure is called it is passed the state returned by the previous call.
DialogBox and DialogBoxIndirect create modal dialogues and do not return until the dialogue procedure calls EndDialog, typically as a result of the user pressing an OK or Cancel button.  CreateDialog and CreateDialogIndirect create modeless dialogues.   The ML implementation automatically ensures that IsDialogMessage is called for modeless dialogues if RunApplication is used.

ML Extension:  Compiles an ML dialogue template into the format used by C.  This can be stored to resource file for later use.

ML Extension: Takes a C format dialogue template structure in memory and returns an ML template.  It can be used where a dialogue template has been loaded from a resource file using LoadResource.