HSCROLL keeps left

[Anonymous]

I am using a HSCROLL control with WM_HSCROLL to pick up the nPosition of the scrollbar. However, when the app is running, i can drag the scroller to the right, but it resets to the left (0) everytime i let go. How can i make it stay?

[Roger Garstang]

Is your code returning %TRUE or some other thing that it is doing that could cause the message to either not be received by Windows or changed?

[gian young]

Please have a look at the following code to see if this helps.

Place this code or what you wish to extract in your WM_HSCROLL Event.

Function FORMMAIN_HSCROLL1_WM_HSCROLL (ControlIndex As Long, hWndForm As Dword, hWndControl As Dword, nScrollCode As Long, nPosition As Long) As Long

   'nScrollCode =
   'SB_BOTTOM   Scrolls To the lower Right.
   'SB_ENDSCROLL   Ends scroll.
   'SB_LINELEFT   Scrolls Left by one unit.
   'SB_LINERIGHT   Scrolls Right by one unit.
   'SB_PAGELEFT   Scrolls Left by the Width Of the window.
   'SB_PAGERIGHT   Scrolls Right by the Width Of the window.
   'SB_THUMBPOSITION   Scrolls To the absolute position. The current position is specified by the nPos parameter.
   'SB_THUMBTRACK   Drags scroll box To the specified position. The current position is specified by the nPos parameter.
   'SB_TOP   Scrolls To the upper Left.
   Local di, ScrollPos As Long
   Local ScrlInfo As SCROLLINFO  
   
   'If Large Change Val = 10 then set nMin to 1 and nMax to 109
   'to get ScrollPos output of 1 - 100

   ScrlInfo.cbSize = SizeOf(ScrlInfo)
   ScrlInfo.fMask = %SIF_ALL
   di = GetScrollInfo(hWndControl, %SB_CTL, ByVal VarPtr(ScrlInfo))
   
   Select Case nScrollCode
      Case %SB_LINELEFT
         If ScrlInfo.nPos > ScrlInfo.nMin Then Decr ScrlInfo.nPos
      Case %SB_LINERIGHT
          If ScrlInfo.nPos < ScrlInfo.nMax Then Incr ScrlInfo.nPos
      Case %SB_THUMBPOSITION
          ScrlInfo.nPos = nPosition
          ScrollPos = nPosition
       Case %SB_PAGELEFT
          If ScrlInfo.nPos > ScrlInfo.nMin + 10 Then
             ScrlInfo.nPos = ScrlInfo.nPos - 10
          Else
              ScrlInfo.nPos = ScrlInfo.nMin
          End If   
       Case %SB_PAGERIGHT
          If ScrlInfo.nPos < ScrlInfo.nMax - 10 Then
             ScrlInfo.nPos = ScrlInfo.nPos + 10
          Else
              ScrlInfo.nPos = ScrlInfo.nMax
          End If              
       Case %SB_ENDSCROLL
           ScrollPos = GetScrollPos(hWndControl, %SB_CTL)
           g_HscrollVal(0) = ScrollPos - 1: 'g_DrawMode = 2

   End Select
   
   di = SetScrollInfo(hWndControl, %SB_CTL, ByVal VarPtr(ScrlInfo), %True)

End Function

Using the API SetScrollInfo function will ensure the slider remains set at the position identified by the variable ScrollPos.

Regards and good luck

Gian Young

Dataman Barcode Systems Australia