OpenEdge Development:<br />Programming Interfaces Instantiating the control

Instantiating the control

The AppBuilder generates the code to instantiate the ActiveX control starting with a call to the enable_UI procedure from the Main Block:

/* ************************* Main Block ************************* / / Parent the dialog-box to the ACTIVE-WINDOW, if there is no parent. / IF VALID-HANDLE(ACTIVE-WINDOW) AND FRAME {&FRAME-NAME}:PARENT eq ? THEN FRAME {&FRAME-NAME}:PARENT = ACTIVE-WINDOW. / Now enable the interface and wait for the exit condition. / / (NOTE: handle ERROR and END-KEY so cleanup code will always fire. / MAIN-BLOCK: DO ON ERROR UNDO MAIN-BLOCK, LEAVE MAIN-BLOCK ON END-KEY UNDO MAIN-BLOCK, LEAVE MAIN-BLOCK: `RUN enable_UI.` / Set max-records from open query in enable_UI. */ `max-records = NUM-RESULTS("Dialog-Frame").` WAIT-FOR GO OF FRAME {&FRAME-NAME}. END. RUN disable_UI.

/* ***************************  Main Block  *************************** */

/* Parent the dialog-box to the ACTIVE-WINDOW, if there is no parent.   */
IF VALID-HANDLE(ACTIVE-WINDOW) AND FRAME {&FRAME-NAME}:PARENT eq ?
THEN FRAME {&FRAME-NAME}:PARENT = ACTIVE-WINDOW.

/* Now enable the interface and wait for the exit condition.            */
/* (NOTE: handle ERROR and END-KEY so cleanup code will always fire.    */
MAIN-BLOCK:
DO ON ERROR   UNDO MAIN-BLOCK, LEAVE MAIN-BLOCK
   ON END-KEY UNDO MAIN-BLOCK, LEAVE MAIN-BLOCK:
    RUN enable_UI.
    
    /* Set max-records from open query in enable_UI. */

    max-records = NUM-RESULTS("Dialog-Frame").
     
    WAIT-FOR GO OF FRAME {&FRAME-NAME}.
END.
RUN disable_UI.

The programmer has added the comments and code that immediately follow the call to enable_UI. Here, they must set max-records to the number of records in the query only after the query is opened (again, in enable_UI), but before the spin button control is available to scan the result. The reason for this becomes clearer in later code fragments.

The following reduction of the enable_UI procedure shows that the AppBuilder generates the code to load the ActiveX control (RUN control_load) before its static parent frame and family of 4GL widgets are displayed and enabled. The initial value of Record_Count is also set at control load time (see the "Initializing the control" section. Note also that the application query is opened to obtain the data for the frame:

/* ******************** Internal Procedures ********************* / . . . PROCEDURE enable_UI : /------------------------------------------------------------------------ Purpose: ENABLE the User Interface Parameters: <none> Notes: Here we display/view/enable the widgets in the user-interface. In addition, OPEN all queries associated with each FRAME and BROWSE. These statements here are based on the "Other Settings" section of the widget Property Sheets. ------------------------------------------------------------------------*/ `RUN control_load`. {&OPEN-QUERY-Dialog-Frame} GET FIRST Dialog-Frame. `DISPLAY Record_Count WITH FRAME Dialog-Frame.` . . . END PROCEDURE.

/* **********************  Internal Procedures  *********************** */
            .
            .
            .
PROCEDURE enable_UI :
/*------------------------------------------------------------------------
  Purpose:     ENABLE the User Interface
  Parameters:  <none>
  Notes:       Here we display/view/enable the widgets in the
               user-interface.  In addition, OPEN all queries
               associated with each FRAME and BROWSE.
               These statements here are based on the "Other 
               Settings" section of the widget Property Sheets.
------------------------------------------------------------------------*/
  RUN control_load.

  {&OPEN-QUERY-Dialog-Frame}
  GET FIRST Dialog-Frame.
  DISPLAY Record_Count 
      WITH FRAME Dialog-Frame.
            .
            .
            .
END PROCEDURE.

Note: You can view this code in the Procedures section of the AppBuilder Section Editor. However, unlike the Main Block, this is protected AppBuilder-generated code that you cannot change.

The control_load procedure, called from enable_UI, is an AppBuilder-generated procedure that loads the ActiveX control into the control-frame by executing the LoadControls( ) method of the control-frame COM object. Note the call to initialize-controls, an optional internal procedure that you can define (and which is defined in this example) to modify control properties before the control becomes visible:

/* ******************** Internal Procedures ********************* / . . . PROCEDURE control_load : /------------------------------------------------------------------------ Purpose: Load the OCXs Parameters: <none> Notes: Here we load, initialize and make visible the OCXs in the interface. ------------------------------------------------------------------------*/ &IF "{&OPSYS}" = "WIN32":U AND "{&WINDOW-SYSTEM}" NE "TTY":U &THEN DEFINE VARIABLE UIB_S AS LOGICAL NO-UNDO. DEFINE VARIABLE OCXFile AS CHARACTER NO-UNDO. OCXFile = SEARCH( "i-ocx1.wrx":U ). IF OCXFile <> ? THEN DO: ASSIGN `chcustSpin = custSpin:COM-HANDLE UIB_S = chcustSpin:LoadControls( OCXFile, "custSpin":U). RUN initialize-controls IN THIS-PROCEDURE NO-ERROR.`END. ELSE MESSAGE "The file, i-ocx1.wrx, could not be found." skip "The controls cannot be loaded." VIEW-AS ALERT-BOX TITLE "Controls Not Loaded". &ENDIF END PROCEDURE.

/* **********************  Internal Procedures  *********************** */
            .
            .
            .
PROCEDURE control_load :
/*------------------------------------------------------------------------
  Purpose:     Load the OCXs    
  Parameters:  <none>
  Notes:       Here we load, initialize and make visible the 
               OCXs in the interface.                        
------------------------------------------------------------------------*/
&IF "{&OPSYS}" = "WIN32":U AND "{&WINDOW-SYSTEM}" NE "TTY":U &THEN
DEFINE VARIABLE UIB_S    AS LOGICAL    NO-UNDO.
DEFINE VARIABLE OCXFile  AS CHARACTER  NO-UNDO.

OCXFile = SEARCH( "i-ocx1.wrx":U ).

IF OCXFile <> ? THEN DO:
  ASSIGN
    chcustSpin = custSpin:COM-HANDLE
    UIB_S = chcustSpin:LoadControls( OCXFile, "custSpin":U).
  RUN initialize-controls IN THIS-PROCEDURE NO-ERROR.
END.
ELSE MESSAGE "The file, i-ocx1.wrx, could not be found." skip
             "The controls cannot be loaded."
             VIEW-AS ALERT-BOX TITLE "Controls Not Loaded".
&ENDIF

END PROCEDURE.

Notes: You can view but not change this AppBuilder-generated code from the Section Editor.

You might wonder why you cannot load the control with a chained handle reference CtrlFrame:COM-HANDLE:LoadControls( ... ). The reason is that even though CtrlFrame:COM-HANDLE returns a component handle, it does so with reference to a widget attribute (COM-HANDLE), not a COM object property or method. You cannot make a component handle expression by chaining widget handle references (that return component handles) with component handle references.