Scrollbar control basics

[Scott Turchin]

I want to put a scrollbar on an app, the scrollbar is NOT attached to any control, it's just there to make a user think he is scrolling through pages of labels/textboxes when in reality I will relabel and reuse those text/label controls...

So I've searched and come up with code but not grasping what i"m doing wr ong, I'm ASSUMING that since I'm using this as a control and not the dialog scroll taht I should treat it like any other control and put it under WM_COMMAND.......no?

Note I'm also only using a vertical scrollbar.
I can also tell something is wrong as it appears to be two scrollbars jammed together, not a nice clean control (It's a visual thing)

In my DIalog Proc
Static hScrollCtl       As Long
Static SB               As SCROLLINFO     


Select Case CbMsg

    Case %WM_INITDIALOG 
        SB.cbSize=SizeOf(SB)
        SB.fMask=%SIF_ALL
        SB.nMin=1
        SB.nMax=100
        SB.nPage=10
        SB.nPos=1
        SB.nTrackPos=0
        SetScrollInfo ByVal hScrollCtl,ByVal %SB_VERT, SB, %TRUE  


     Case %WM_COMMAND
      Select Case LoWrd(CbWParam)
          Case %IDVSCROLL
              GetScrollInfo hScrollCtl, %SB_VERT, SB
              Local oldPos   As Long
              oldPos = SB.nPos
              Select Case LoWrd(CbWParam)
                  Case %SB_LINEDOWN
                      SB.nPos = SB.nPos + 1
                  Case %SB_PAGEDOWN
                    SB.nPos = SB.nPos + SB.nPage
                Case %SB_LINEUP
                    SB.nPos = SB.nPos - 1
                Case %SB_PAGEUP
                    SB.nPos = SB.nPos - SB.nPage
                Case %SB_THUMBTRACK
                    SB.nPos = HiWrd(CbWParam)
                Case Else
                    Exit Function
              End Select
              SB.fMask = %SIF_POS
              SetScrollInfo hScrollCtl, %SB_VERT, SB, 1
              ScrollWindow hScrollCtl, 0, oldPos - SB.nPos, ByVal %NULL, ByVal %NULL

[Michael Mattias]

I'm ASSUMING that since I'm using this as a control and not the dialog scroll taht I should treat it like any other control and put it under WM_COMMAND.......no?

No. You should be looking for WM_HSCROLL and/or WM_VSCROLL (in your case only the WM_VSCROLL ) notification messages to detect events (clicks or keyboard action) occuring on the scrollbars.

The WM_VSCROLL message is sent to a window when a scroll event occurs in the window's standard vertical scroll bar. This message is also sent to the owner of a vertical scroll bar control when a scroll event occurs in the control.

See your WinApi reference for more details.

MCM
PS
>Static hScrollCtl As Long

FWIW, not necessary to keep as a STATIC. You can always get 'when needed' with GetDlgItem(hWnd, %ID_SCROLLBAR) or CONTROL HANDLE hDlg, %ID_SCROLLBAR

[Rodney Hicks]

Try CASE %WM_VSCROLL in the SELECT CASE CBMSG block.

Of course Michael's help is a tad more specific

[Michael Mattias]

WM_VSCROLL
...
lParam
If the message is sent by a scroll bar, this parameter is the handle to the scroll bar control. If the message is not sent by a scroll bar, this parameter is NULL.

[Scott Turchin]

OK Got the point but still can't get the message...
I put MSGBOX's in to verify - no go.....

    Case %WM_INITDIALOG    
        SB.cbSize=SizeOf(SB)
        SB.fMask=%SIF_ALL
        SB.nMin=0
        SB.nMax=100
        SB.nPage=10
        SB.nPos=10
        SB.nTrackPos=10
        SetScrollInfo GetDlgItem(CbHndl,%IDVSCROLL),ByVal %SB_VERT, SB, %TRUE


     Case %WM_VSCROLL
         SB.cbSize=SizeOf(SB)
         SB.fMask=%SIF_ALL
         GetScrollInfo GetDlgItem(CbHndl,%IDVSCROLL), %SB_VERT, SB
         Select Case LoWrd(CbLParam)
             Case %SB_LINEDOWN
                 SB.nPos=SB.nPos + 1
                 MsgBox "Down"
             Case %SB_LINEUP
                 SB.nPos=SB.nPos - 1
                 MsgBox "Up"
             Case %SB_PAGEDOWN
                 SB.nPos=SB.nPos+SB.nPage
                 MsgBox "Down"
             Case %SB_PAGEUP
                 SB.nPos=SB.nPos-SB.nPage
                 MsgBox "Up"
             Case %SB_THUMBPOSITION
                 SB.nPos=SB.nTrackPos
             Case %SB_THUMBTRACK
                 SB.nPos=SB.nTrackPos
             Case Else
                 Exit Function
         End Select
         SetScrollInfo GetDlgItem(CbHndl,%IDVSCROLL),ByVal %SB_VERT, SB, %TRUE

[Michael Mattias]

 Case %WM_VSCROLL
         SB.cbSize=SizeOf(SB)
         SB.fMask=%SIF_ALL
         GetScrollInfo GetDlgItem(CbHndl,%IDVSCROLL), %SB_VERT, SB
[b]        [COLOR="Red"]Select Case LoWrd(CbLParam[/COLOR])[/b]   '   Use wrong value so routine won't work.
            Case %SB_LINEDOWN

What does your doc say about wParam and lparam for WM_VSCROLL notification?

MCM

[Scott Turchin]

What doc?

[Michael Mattias]

What doc?

Whatever you use for your Windows API documentation,that's what doc.

Ain't got nuttin' local? Start here: http://msdn.microsoft.com/en-us/default.aspx

[Rodney Hicks]

This I found in the forums, but I don't know who put it there, it does a good job with scrollbars and easy to understand, adapt, and adopt.

#PBFORMS CREATED V1.51
'--------------------------------------------------------------------------------------------------
' The first line in this file is a PB/Forms metastatement.
' It should ALWAYS be the first line of the file. Other
' PB/Forms metastatements are placed at the beginning and
' end of "Named Blocks" of code that should be edited
' with PBForms only. Do not manually edit or delete these
' metastatements or PB/Forms will not be able to reread
' the file correctly.  See the PB/Forms documentation for
' more information.
' Named blocks begin like this:    #PBFORMS BEGIN ...
' Named blocks end like this:      #PBFORMS END ...
' Other PB/Forms metastatements such as:
'     #PBFORMS DECLARATIONS
' are used by PB/Forms to insert additional code.
' Feel free to make changes anywhere else in the file.
'--------------------------------------------------------------------------------------------------

#COMPILE EXE
#DIM ALL

'--------------------------------------------------------------------------------------------------
'   ** Includes **
'--------------------------------------------------------------------------------------------------
#PBFORMS BEGIN INCLUDES 
#IF NOT %DEF(%WINAPI)
  #INCLUDE "WIN32API.INC"
#ENDIF
#PBFORMS END INCLUDES
'--------------------------------------------------------------------------------------------------

'--------------------------------------------------------------------------------------------------
'   ** Constants **
'--------------------------------------------------------------------------------------------------
#PBFORMS BEGIN CONSTANTS 
%IDD_DIALOG1 =  101
%IDC_LABEL1  = 1001
%IDC_LABEL2  = 1002
%IDC_LABEL3  = 1003
%IDC_HELPME  = 1004
#PBFORMS END CONSTANTS
'--------------------------------------------------------------------------------------------------

'--------------------------------------------------------------------------------------------------
'   ** Declarations **
'--------------------------------------------------------------------------------------------------
DECLARE CALLBACK FUNCTION ShowDIALOG1Proc()
DECLARE FUNCTION ShowDIALOG1(BYVAL hParent AS DWORD) AS LONG
#PBFORMS DECLARATIONS
'--------------------------------------------------------------------------------------------------

'--------------------------------------------------------------------------------------------------
'   ** Main Application Entry Point **
'--------------------------------------------------------------------------------------------------
FUNCTION PBMAIN()
  ShowDIALOG1 %HWND_DESKTOP
END FUNCTION
'--------------------------------------------------------------------------------------------------

'--------------------------------------------------------------------------------------------------
'   ** CallBacks **
'--------------------------------------------------------------------------------------------------
CALLBACK FUNCTION ShowDIALOG1Proc()
  LOCAL w AS LONG, h AS LONG, oldPos AS LONG, si AS SCROLLINFO
  LOCAL vt AS LONG, ht AS LONG, hs AS LONG, vs AS LONG
  w=600
  h=400
  vt=50
  ht=50
  hs=5
  vs=5
  SELECT CASE AS LONG CBMSG
    CASE %WM_INITDIALOG
      ' Initialization handler
      si.cbSize=LEN(si)
      si.fMask=%SIF_ALL
      si.nMin=0
      si.nMax=h
      si.nPage=vt
      SetScrollInfo CBHNDL, %SB_VERT, si, 1
      si.nMin=0
      si.nMax=w
      si.nPage=ht
      si.nPos=0
      SetScrollInfo CBHNDL, %SB_HORZ, si, 1

    CASE %WM_NCACTIVATE
      STATIC hWndSaveFocus AS DWORD
      IF ISFALSE CBWPARAM THEN
        ' Save control focus
        hWndSaveFocus = GetFocus()
      ELSEIF hWndSaveFocus THEN
        ' Restore control focus
        SetFocus(hWndSaveFocus)
        hWndSaveFocus = 0
      END IF

    CASE %WM_COMMAND
      ' Process control notifications
      SELECT CASE AS LONG CBCTL
        CASE %IDC_LABEL1

        CASE %IDC_LABEL2

        CASE %IDC_LABEL3

      END SELECT
    CASE %WM_HSCROLL
      si.cbSize=SIZEOF(si)
      si.fMask=%SIF_ALL
      GetScrollInfo CBHNDL, %SB_HORZ, si
      oldPos=si.nPos
      SELECT CASE LOWRD(CBWPARAM)
        CASE %SB_LINELEFT
          si.nPos=si.nPos-hs
        CASE %SB_PAGELEFT
          si.nPos=si.nPos=si.nPage
        CASE %SB_LINERIGHT
          si.nPos=si.nPos+hs
        CASE %SB_PAGERIGHT
          si.nPos=si.nPos+si.nPage
        CASE %SB_THUMBTRACK
          si.nPos=HIWRD(CBWPARAM)
        CASE ELSE
          EXIT FUNCTION
      END SELECT
      si.nPos=MAX&(si.nMin, MIN&(si.nPos, si.nMax-si.nPage))
      si.fMask=%SIF_POS
      SetScrollInfo CBHNDL,%SB_HORZ,si,1
      ScrollWindow CBHNDL, oldPos-si.nPos,0,BYVAL %NULL, BYVAL %NULL
      FUNCTION = 1

    CASE %WM_VSCROLL
      si.cbSize=SIZEOF(si)
      si.fMask=%SIF_ALL
      GetScrollInfo CBHNDL, %SB_VERT, si
      oldPos=si.nPos
      SELECT CASE LOWRD(CBWPARAM)
        CASE %SB_LINEUP
          si.nPos=si.nPos-vs
        CASE %SB_PAGEUP
          si.nPos=si.nPos-si.nPage
        CASE %SB_LINEDOWN
          si.nPos=si.nPos+vs
        CASE %SB_PAGEDOWN
          si.nPos=si.nPos+si.nPage
        CASE %SB_THUMBTRACK
          si.nPos=HIWRD(CBWPARAM)
        CASE ELSE
          EXIT FUNCTION
      END SELECT
      si.nPos=MAX&(si.nMin, MIN&(si.nPos, si.nMax-si.nPage+1))
      si.fMask=%SIF_POS
      SetScrollInfo CBHNDL, %SB_VERT, si, 1
      ScrollWindow CBHNDL,0, oldPos-si.nPos,BYVAL %NULL, BYVAL %NULL
      FUNCTION = 1
  END SELECT
END FUNCTION
'--------------------------------------------------------------------------------------------------

'--------------------------------------------------------------------------------------------------
'   ** Dialogs **
'--------------------------------------------------------------------------------------------------
FUNCTION ShowDIALOG1(BYVAL hParent AS DWORD) AS LONG
  LOCAL lRslt AS LONG

#PBFORMS BEGIN DIALOG %IDD_DIALOG1->->
  LOCAL hDlg  AS DWORD

  DIALOG NEW hParent, "SCROLLER", 359, 88, 283, 359, %WS_POPUP OR %WS_BORDER OR %WS_DLGFRAME OR _
    %WS_SYSMENU OR %WS_MINIMIZEBOX OR %WS_MAXIMIZEBOX OR %WS_CLIPSIBLINGS OR %WS_VSCROLL OR _
    %WS_VISIBLE OR %DS_MODALFRAME OR %DS_3DLOOK OR %DS_NOFAILCREATE OR %DS_SETFONT, _
    %WS_EX_CONTROLPARENT OR %WS_EX_LEFT OR %WS_EX_LTRREADING OR %WS_EX_RIGHTSCROLLBAR, TO hDlg
  CONTROL ADD LABEL,  hDlg, %IDC_LABEL1, "Label1", 5, 5, 100, 10
  CONTROL ADD LABEL,  hDlg, %IDC_LABEL2, "510 LEFT", 510, 260, 100, 10
  CONTROL ADD LABEL,  hDlg, %IDC_LABEL3, "405BOTTOM", 10, 305, 100, 10
  CONTROL ADD BUTTON, hDlg, %IDC_HELPME, "HELP", 475, 130, 50, 15
#PBFORMS END DIALOG

  DIALOG SHOW MODAL hDlg, CALL ShowDIALOG1Proc TO lRslt

#PBFORMS BEGIN CLEANUP %IDD_DIALOG1
#PBFORMS END CLEANUP

  FUNCTION = lRslt
END FUNCTION
'--------------------------------------------------------------------------------------------------

[Michael Mattias]

      GetScrollInfo CBHNDL, %SB_VERT, si

This gets scroll info for the scrollbar which is part of the dialog, not a child scrollbar control, which is what this question is about.

See your documentation for more details.

[Scott Turchin]

Using my code above I REM'd out the initial SETSCROLLINFO and amazing enough the scrollbar "Looks" normal now, not like a shadow on another one.
But as soon as I click it and do the SETSCROLLINFO it takes on that form and stops functioning....I think I"mdoing it correctly but I have a conflict of some kind...

[Michael Mattias]

> [on WM_INITDIALOG]
> SetScrollInfo ByVal hScrollCtl,ByVal %SB_VERT, SB, %TRUE

Value of hScrollCtl was not set prior to this call in WM_INITDIALOG.

When SetScrollInfo is called later after adjustment, SB values must be adjusted based in the settings used in SetScrollinfo... i.e. you must adjust your 'scroll position' based in the current page and position within the page. i.e, it is unlikely SB_LINEDOWN will correspond to exactly one "scroll unit" as set with SetScrollInfo, even if you had properly called SetScrollInfo with a valid control handle on WM_INITDIALOG.

But it looks like you are getting closer.

[Scott Turchin]

I did a Control Handle cbhndl, %IDVSCROLL to hScrollCtl but forgot to paste it.

THe weird part is, and I wish I could take a picture and send you, AFTER I do the SetScroll, the scrollbar gets thinner and looks like a second one underneath it, UNLESS I do that byval stuff and even then it only works once and goes back to it again....

[Michael Mattias]

>wish I could take a picture and send you

Well, next best thing - actually a better thing when you think about it - make up a little one-screen demo program.

I assume what we don't see in code posted so far is when you get WM_VSCROLL, you scroll some other control containing text and/or pictures.

And, if the user uses he keyboard to scroll in that other control, you want to reset the external scrollbar so the thumb stays about where it belongs relative to "how far down the list" the user has scrolled.

Surely you can cut and paste a few pieces from what you've got and post it here for others to play with?

MCM

[Scott Turchin]

Ya can do, except it appears I have resolved that issue.......

The handle to the scrollbar must be passed byval or it acts WEIRD....

SetScrollInfo byval varptr(scrollhandle) etc etc....

Tx!

[Scott Turchin]

This works almost flawlessly....debug time 2nite..

%IDVSCROLL          = %WM_USER + 208

Winmain:
Control Add ScrollBar, g_hDlg,%IDVSCROLL,"",410,150,10,60

DialogProc:

Local  SB               As SCROLLINFO
Static PageNo           As Long
Local  cStart           As Long
Local  cStop            As Long

Select Case CbMsg
    Case %WM_INITDIALOG
        Control Handle CbHndl, %IDVSCROLL To g_hScroll
        SB.cbSize=SizeOf(SB)
        SB.fMask=%SIF_ALL
        SB.nMin=0
        SB.nMax=100
        SB.nPage=10
        SB.nPos=10
        SB.nTrackPos=10
        SetScrollInfo ByVal VarPtr(g_hScroll) ,%SB_VERT, SB, %TRUE
        PageNo = 1

     Case %WM_VSCROLL
         SB.cbSize=SizeOf(SB)
         SB.fMask=%SIF_ALL
         GetScrollInfo ByVal VarPtr(g_hScroll), %SB_VERT, SB
         Select Case LoWrd(CbWParam)

             Case %SB_LINEDOWN
                 SB.nPos=SB.nPos + 1
                 If PageNo = 10 Then  'Can't go past page 10
                     Exit Function
                 Else
                     Incr PageNo
                     cStart = PageNo * 10
                     cStop = (PageNo * 10) + 10
'                     MsgBox "cStart: " & Format$(cStart) & $CrLf & "cStop: " & Format$(cStop)
                     For lLoop = cStart To cStop 'Change variables on the page
                         Incr lCount
                         sTmp = "Command " & Format$(lLoop)
                         Control Set Text CbHndl, %COMMANDLABEL0 + lCount,sTmp
                         sTmp = Commands(lLoop)
                         Control Set Text CbHndl, %COMMAND0 + lCount,sTmp
                     Next
                End If

             Case %SB_LINEUP
                 SB.nPos=SB.nPos - 1
                 If PageNo = 1 Then
                     Exit Function
                 Else
                     Decr PageNo
                     cStart = PageNo * 10
                     cStop = (PageNo * 10) + 10
'                     MsgBox "cStart: " & Format$(cStart) & $CrLf & "cStop: " & Format$(cStop)
                     For lLoop = cStart To cStop
                         Incr lCount
                         sTmp = "Command " & Format$(lLoop)
                         Control Set Text CbHndl, %COMMANDLABEL0 + lCount,sTmp
                         sTmp = Commands(lLoop)
                         Control Set Text CbHndl, %COMMAND0 + lCount,sTmp
                     Next
                 End If

             Case %SB_PAGEDOWN
                 SB.nPos=SB.nPos+SB.nPage
                 If PageNo = 10 Then  'Can't go past page 10
                     Exit Function
                 Else
                     Incr PageNo
                     cStart = PageNo * 10
                     cStop = (PageNo * 10) + 10
'                     MsgBox "cStart: " & Format$(cStart) & $CrLf & "cStop: " & Format$(cStop)
                     For lLoop = cStart To cStop 'Change variables on the page
                         Incr lCount
                         sTmp = "Command " & Format$(lLoop)
                         Control Set Text CbHndl, %COMMANDLABEL0 + lCount,sTmp
                         sTmp = Commands(lLoop)
                         Control Set Text CbHndl, %COMMAND0 + lCount,sTmp
                     Next
                End If

             Case %SB_PAGEUP
                 SB.nPos=SB.nPos-SB.nPage
                 SB.nPos=SB.nPos - 1
                 If PageNo = 1 Then
                     Exit Function
                 Else
                     Decr PageNo
                     cStart = PageNo * 10
                     cStop = (PageNo * 10) + 10
                     MsgBox "cStart: " & Format$(cStart) & $CrLf & "cStop: " & Format$(cStop)
                     For lLoop = cStart To cStop
                         Incr lCount
                         sTmp = "Command " & Format$(lLoop)
                         Control Set Text CbHndl, %COMMANDLABEL0 + lCount,sTmp
                         sTmp = Commands(lLoop)
                         Control Set Text CbHndl, %COMMAND0 + lCount,sTmp
                     Next
                 End If
             Case %SB_THUMBPOSITION
                 SB.nPos=SB.nTrackPos
             Case %SB_THUMBTRACK
                 SB.nPos=SB.nTrackPos
             Case Else
                 Exit Function
         End Select
         SetScrollInfo ByVal VarPtr(g_hScroll),ByVal %SB_VERT, SB, %TRUE

[Michael Mattias]

>SetScrollInfo ByVal VarPtr(g_hScroll) ,%SB_VERT, SB, %TRUE

Time to re-

When GetScrollInfo and SetScrollInfo are used for a standalone control, what is the correct value to use for parameter two? (Hint: it is not %SB_VERT!)

And BYVAL VARPTR(g_hScroll) is not correct. That handle should be passed by value, not by reference ("BYVAL VARPTR()" = "BYREF")

(FWIW, you do not need to save that handle in a global variable. It comes as lparam on every WM_SCROLL notification from a standalone scrollbar control)

MCM

[Scott Turchin]

DId not know that!
I'll see if I can test that here today, odds are it will be a few days - I will be back though!! Company flying in....ugh...

[Scott Turchin]

>SetScrollInfo ByVal VarPtr(g_hScroll) ,%SB_VERT, SB, %TRUE

Time to re-

When GetScrollInfo and SetScrollInfo are used for a standalone control, what is the correct value to use for parameter two? (Hint: it is not %SB_VERT!)

And BYVAL VARPTR(g_hScroll) is not correct. That handle should be passed by value, not by reference ("BYVAL VARPTR()" = "BYREF")

(FWIW, you do not need to save that handle in a global variable. It comes as lparam on every WM_SCROLL notification from a standalone scrollbar control)

MCM

OK Mike ya got me, what are the answers for parameter 2 then????

Did not know about lparam but that would be easier to work with so I will change and test!

Tx!

[Michael Mattias]

>OK Mike ya got me, what are the answers for parameter 2 then????

!!!

Check your WinAPI doc for WM_HSCROLL, WM_VSCROLL, GetScrollInfo and SetScrollInfo.

And while you're at it, check the doc under CONTROL ADD SCROLLBAR in your compiler help file. It even tells you explicitly there to be careful to avoid making the mistake of using SB_VERT or SB_HORZ!!

(Now that we know this is DDT rather than SDK style I can point you there).

In fairness... there is some bad inconsistency on that help file page as well. First, the syntax for CONTROL ADD SCROLLBAR allows you to enter a "txt$" parameter, although that text is never shown (cleverly explained away in the text of the help, however) ; second, it supports a CALLBACK option allowing you to have a control-level callback function WHICH CAN NEVER BE CALLED. (Surprise!).

MCM