Controlling a control's scroll bar

[dragonjim]

Hi,

I wonder if anyone could tell me how to manipulate the scrollbar on a TextBox / ListView OCX control.

Thanks for any help

[649psoft2]

use the win32 API

GetScrollInfo
GetScrollRange
SetScrollInfo
SetScrollPos
SetScrollRange
WM_HSCROLL
WM_VSCROLL

[dragonjim]

Thanks for that...however, I'm having some trouble getting them to work without an Access Violation Error.

My trial program is as below (concatenated to make it shorter):

Type SCROLLINFO
cbSize As Integer : fMask As Integer : nMin As Integer : nMax As Integer : nPage As Integer : nPos As Integer : nTrackPos As Integer
EndType

'Declare Function GetScrollInfo Lib "User32.dll" (ByVal Hdl As Handle, ByVal fnbar As Integer, info As SCROLLINFO) As Integer
'Declare Function SetScrollInfo Lib "User32.dll" (ByVal Hdl As Handle, ByVal fnbar As Integer, ByVal nPos As Integer, ByVal Redraw As Boolean)

OpenW 1
Ocx ListView win1_lv1 = , 100, 100, 400, 200
win1_lv1.View = 3
Local a$, m, n
Dim ch As ColumnHeader
For n = 1 To 4
Set ch = win1_lv1.ColumnHeaders.Add( , n, "Column " & n)
Next n
For n = 1 To 100
win1_lv1.Add , n , "" : a$ = ""
For m = 1 To 4 : a$ = a$ & "Col " & m & " Row " & n & ";" : Next m
win1_lv1(n).AllText = a$
Next n

Dim sinfo As SCROLLINFO
Local b = GetScrollInfo(win1_lv1.hWnd, SB_VERT, sinfo)
Print b
Print sinfo.cbSize : Print sinfo.fMask : Print sinfo.nMin : Print sinfo.nMax : Print sinfo.nPage
Print sinfo.nPos : Print sinfo.nTrackPos

~SetScrollInfo(win1_lv1.hWnd, SB_VERT, 600, True)

Do
Sleep
Until Win_1 Is Nothing

As you can see I have tried declaring the Windows API functions, as well as using the GFA application of these functions.

With the first, the Access Violation error occurs with both GetScrollInfo and SetScrollInfo, while with the second, only with SetScrollInfo.

I would appreciate any guidance as to where I am going wrong.

[649psoft2]

I rewrote your example.

According to MSDN the cbSize cbSize nPage members of
the SCROLLINFO structure are UINT and Long is used in
gb32.

Also according to MSDN SetScrollInfo sets the values in the
structure but does not sent the message to the scrollbar window.

Sendmessage is used to move the listview scrollbar.

The third parameter in SetScrollInfo is the pointer to the
SCROLLINFO structure.

Type SCROLLINFO
cbSize As Long
fMask As Long
nMin As Int
nMax As Int
nPage As Long
nPos As Int
nTrackPos As Int
End Type

OpenW 1
Ocx ListView win1_lv1 = , 100, 100, 400, 200
win1_lv1.View = 3
Local a$, m, n
Dim ch As ColumnHeader
For n = 1 To 4
Set ch = win1_lv1.ColumnHeaders.Add( , n, "Column " & n)
Next n
For n = 1 To 100
win1_lv1.Add , n , "" : a$ = ""
For m = 1 To 4 : a$ = a$ & "Col " & m & " Row " & n & ";" : Next m
win1_lv1(n).AllText = a$
Next n

Dim sinfo As SCROLLINFO

'Local b = GetScrollInfo(win1_lv1.hWnd, SB_VERT, sinfo)
'Print b
'Print sinfo.cbSize : Print sinfo.fMask : Print sinfo.nMin : Print sinfo.nMax : Print sinfo.nPage
'Print sinfo.nPos : Print sinfo.nTrackPos

'sets parameters in the SCROLLINFO structure
'but does not send a message to a window

~SetScrollInfo(win1_lv1.hWnd, SB_VERT, V:sinfo, 0)
Local n&
For n& = 1 To 50
~SendMessage(win1_lv1.hWnd, WM_VSCROLL, SB_VERT, 0)
Next n&

Do : Sleep : Until Win_1 Is Nothing

[dragonjim]

Once again, much obliged for your help.

I noticed the UInt (or unsigned integer) in the MSDN documentation but saw a VB example where they exchanged them for Integer variables - hence the error.

I am also now aware that I could use the EnsureVisible Method on the ListView control, but this doesn't help if the subitem or column selected is off the screen horizontally (i.e. the list is wider than the screen).

Thank you again for your help. It is, as always, much appreciated.