The OpenEdge Hive

Progress frames and windows show both scrollbars or none.
It would be better if the scrollbars were shown independently.
The procedure ShowScrollbarsWhenNeeded is to be called 'on end-size' or during initialize.
The procedure HideScrollbars does simply that: hide both scrollbars whether or not the virtual size is larger than the actual size. The procedure is mainly a demonstration of the {&SB_BOTH} constant.

{windows.i}
 
PROCEDURE ShowScrollbarsWhenNeeded :
/* purpose : to be called from "on end-size" or whenever. */
   DEFINE INPUT PARAMETER hFrame AS HANDLE.
 
   DEFINE VARIABLE retval AS INTEGER NO-UNDO.
   IF hFrame:VIRTUAL-WIDTH-PIXELS > hFrame:WIDTH-PIXELS THEN
      RUN ShowScrollBar IN hpApi (hFrame:HWND, 
                                  {&SB_HORZ}, 
                                   -1,
                                  OUTPUT retval).
   ELSE
      RUN ShowScrollBar IN hpApi (hFrame:HWND, 
                                  {&SB_HORZ},  
                                  0,
                                  OUTPUT retval).
 
   IF hFrame:VIRTUAL-HEIGHT-PIXELS > hFrame:HEIGHT-PIXELS THEN
      RUN ShowScrollBar IN hpApi (hFrame:HWND, 
                                  {&SB_VERT}, 
                                  -1,
                                  OUTPUT retval).
   ELSE
      RUN ShowScrollBar IN hpApi (hFrame:HWND, 
                                  {&SB_VERT},  
                                  0,
                                  OUTPUT retval).
 
END PROCEDURE.
 
 
PROCEDURE HideScrollbars :
/* purpose : hide both scrollbars */
   DEFINE INPUT PARAMETER hFrame AS HANDLE.
 
   DEFINE VARIABLE retval AS INTEGER NO-UNDO.
   RUN ScrollUpperLeft(hFrame).
   RUN ShowScrollBar IN hpApi (hFrame:HWND, 
                               {&SB_BOTH},
                               0,
                               OUTPUT retval).
 
END PROCEDURE.
 
PROCEDURE ScrollUpperLeft :
/* purpose : move both scrollbars to their 0% position */
   DEFINE INPUT PARAMETER hFrame AS HANDLE.
 
   DEFINE VARIABLE wParam AS INTEGER NO-UNDO.
   DEFINE VARIABLE nPos AS INTEGER   NO-UNDO.
   DEFINE VARIABLE RetVal AS INTEGER NO-UNDO.
   nPos = 0.                       
   wParam = (nPos * 256) + {&SB_THUMBPOSITION}.
   RUN SendMessage{&A} IN hpApi (hFrame:HWND, {&WM_HSCROLL}, wParam, 0, OUTPUT RetVal).
   RUN SendMessage{&A} IN hpApi (hFrame:HWND, {&WM_VSCROLL}, wParam, 0, OUTPUT RetVal).
 
END PROCEDURE.

Explanation:

In procedure ScrollUpperleft, wParam has SB_THUMBPOSITION in its low byte to let windows know that you want to do something with the thumb position. The wanted position (nPos=0) is placed in the high byte by multiplying it by 256.
Frankly I only tried the value nPos=0 so I might as well have assigned
wParam = {&SB_THUMBPOSITION}.
For any other value for nPos you should test if the factor '256' is adequate for both 16-bits and 32-bits versions! (I guess not).

Easier ways to scroll

{windows.i}
DEFINE VARIABLE RetVal AS INTEGER NO-UNDO.
 
&GLOBAL-DEFINE SB_PAGEUP 2
&GLOBAL-DEFINE SB_PAGEDOWN 3
&GLOBAL-DEFINE SB_TOP 6
 
PROCEDURE ScrollUpperLeft :
/* purpose : move both scrollbars to their 0% position */
   DEFINE INPUT PARAMETER hFrame AS HANDLE.
 
   RUN SendMessage{&A} IN hpApi (hFrame:HWND, {&WM_HSCROLL}, {&SB_TOP}, 0, OUTPUT RetVal).
   RUN SendMessage{&A} IN hpApi (hFrame:HWND, {&WM_VSCROLL}, {&SB_TOP}, 0, OUTPUT RetVal).
 
END PROCEDURE.
 
PROCEDURE PageDown :
   DEFINE INPUT PARAMETER hFrame AS HANDLE.
 
   RUN SendMessage{&A} IN hpApi (hFrame:HWND, {&WM_VSCROLL}, {&SB_PAGEDOWN}, 0, OUTPUT RetVal).
 
END PROCEDURE.
 
PROCEDURE PageUp :
   DEFINE INPUT PARAMETER hFrame AS HANDLE.
 
   RUN SendMessage{&A} IN hpApi (hFrame:HWND, {&WM_VSCROLL}, {&SB_PAGEUP}, 0, OUTPUT RetVal).
 
END PROCEDURE.