My application uses the ListView control and allows users to drag column
headers and change their width. Of course the user wants these changes saved
so every time I show a different list (with different column headers) I save
the width and order of all columns.

Most users will drag the columns just a few times and will then leave them
alone. So 99 of a 100 times I'm saving the information for nothing.

Does anybody know how to detect changes in columnheader position and width
so I can save them only when needed?

Roel de Regt

Hi Roel.  You can subclass the ListView and look for several of the Header Control
Notification Messages.  You'll probably be primarily interested in the HDN_ENDTRACK
(user has finished dragging a divider), HDN_DIVIDERDBLCLICK (user double-clicked the
divider area of the control), and HDN_ENDDRAG (re-ordered drag operation has ended).
I've provided some sample code below (tested on VB6).  For definitions of the Header
messages, see the following link:

Header Control Notification Messages
http://msdn.microsoft.com/library/sdkdoc/shellcc/commctls/Header/Noti...
cations.htm

The following article may be of some assistance as well:

How to Determine Re-Ordered Column Positions in a ListView
http://mvps.org/vbnet/code/comctl/lvcolumnpos.htm

'=============================
'Begin Module Code
Option Explicit

Public Const WM_NOTIFY = &H4E
Public Const GWL_WNDPROC = -4

Public lpPrevWndProc As Long
Public gHW As Long

Public Declare Function CallWindowProc Lib "user32" Alias _
"CallWindowProcA" (ByVal lpPrevWndFunc As Long, _
ByVal hwnd As Long, ByVal Msg As Long, _
ByVal wParam As Long, ByVal lParam As Long) As Long

Public Declare Function SetWindowLong Lib _
"user32" Alias "SetWindowLongA" _
(ByVal hwnd As Long, ByVal nIndex As Long, _
ByVal dwNewLong As Long) As Long

Public Declare Sub MoveMemory Lib _
"kernel32" Alias "RtlMoveMemory" _
(pDest As Any, pSource As Any, _
ByVal dwLength As Long)

'The NMHDR structure contains information
'about a notification message.
'The pointer to this structure is specified as
'the lParam member of the WM_NOTIFY message.
Private Type NMHDR
hwndFrom As Long   ' Window handle of control sending message
idFrom As Long        ' Identifier of control sending message
code  As Long          ' Specifies the notification code
End Type

Private Type NMHEADER
   hdr As NMHDR
   iItem As Long
   iButton As Long
   lPtrHDItem As Long '    HDITEM  FAR* pItem
End Type

'Header Notifications
'HDN_BEGINDRAG           Drag operation has begun
'HDN_BEGINTRACK          User began dragging a divider
'HDN_DIVIDERDBLCLICK     User double clicked the divider area
'HDN_ENDDRAG         Drag operation has ended
'HDN_ENDTRACK            User finished dragging a divider
'HDN_GETDISPINFO     Item information request
'HDN_ITEMCHANGED     An item has changed
'HDN_ITEMCHANGING        An item is changing
'HDN_ITEMCLICK           User clicked the control
'HDN_ITEMDBLCLICK        User double-clicked the control
'HDN_TRACK           User is dragging a divider
'NM_CUSTOMDRAW       Custom draw request notification
'NM_RCLICK           User clicked right mouse button in control
'NM_RELEASEDCAPTURE      Control is releasing mouse capture

Public Enum HD_Notifications
  HDN_FIRST = -300&
  HDN_LAST = -399&
  HDN_GETDISPINFO = (HDN_FIRST - 9)
  HDN_BEGINDRAG = (HDN_FIRST - 10)
  HDN_ENDDRAG = (HDN_FIRST - 11)
  HDN_ITEMCLICK = (HDN_FIRST - 2)
  HDN_ITEMDBLCLICK = (HDN_FIRST - 3)
  HDN_DIVIDERDBLCLICK = (HDN_FIRST - 5)
  HDN_ITEMCHANGING = (HDN_FIRST - 0)
  HDN_ITEMCHANGED = (HDN_FIRST - 1)
  HDN_BEGINTRACK = (HDN_FIRST - 6)
  HDN_ENDTRACK = (HDN_FIRST - 7)
  HDN_TRACK = (HDN_FIRST - 8)
  NM_FIRST = -0&              ' (0U-  0U)
  NM_CUSTOMDRAW = (NM_FIRST - 12)
  NM_RCLICK = (NM_FIRST - 5)
  NM_RELEASEDCAPTURE = (NM_FIRST - 16)
End Enum
Public Sub Hook()
'Establish a hook to capture messages to this window
lpPrevWndProc = SetWindowLong(gHW, _
GWL_WNDPROC, _
AddressOf WindowProc)
End Sub

Public Sub Unhook()
Dim temp As Long
'Reset the message handler for this window
temp = SetWindowLong(gHW, _
GWL_WNDPROC, lpPrevWndProc)
End Sub

Function WindowProc(ByVal hwnd As Long, ByVal uMsg As Long, _
ByVal wParam As Long, ByVal lParam As Long) As Long

Dim nmh As NMHDR
Dim nmhd As NMHEADER

Select Case uMsg

    Case WM_NOTIFY

        ' Fill the NMHDR struct from the lParam pointer.
        ' (for any WM_NOTIFY msg, lParam always points to a struct which is
        '  either the NMHDR struct, or whose 1st member is the NMHDR struct)
        Call MoveMemory(nmh, ByVal lParam, Len(nmh))
        ' Fill the NMHEADER struct from the lParam pointer.
        Call MoveMemory(nmhd, ByVal lParam, Len(nmhd))

        Select Case nmh.code

            Case HDN_BEGINTRACK 'User began dragging a divider

                ' nmhd.iItem will tell you which divider is being dragged
                ' 0 based
                Debug.Print "HDN_BEGINTRACK: " & nmhd.iItem

            Case HDN_TRACK           'User is dragging a divider
                ' nmhd.iItem will tell you which divider is being dragged
                ' 0 based
                Debug.Print "HDN_TRACK: " & nmhd.iItem

            Case HDN_ENDTRACK            'User finished dragging a divider
                ' nmhd.iItem will tell you which divider is finished being dragged
                ' 0 based
                Debug.Print "HDN_ENDTRACK: " & nmhd.iItem

            Case HDN_DIVIDERDBLCLICK 'User double clicked the divider area
                ' nmhd.iItem will tell you which divider is being double clicked
                ' 0 based
                Debug.Print "HDN_DIVIDERDBLCLICK: " & nmhd.iItem

            Case HDN_BEGINDRAG           'Drag operation has begun
                ' nmhd.iItem will tell you which divider is being dragged
(re-ordered)
                ' 0 based
                Debug.Print "HDN_BEGINDRAG: " & nmhd.iItem

            Case HDN_ENDDRAG         'Drag operation has ended
                ' nmhd.iItem will tell you which divider is finished being dragged
(re-ordered)
                ' 0 based
                Debug.Print "HDN_ENDDRAG: " & nmhd.iItem

        End Select

End Select

'Pass message on to the original window message handler
WindowProc = CallWindowProc(lpPrevWndProc, hwnd, _
uMsg, wParam, lParam)
End Function

'End Module Code
'=============================
'Begin Form Code
Private Sub Form_Load()
'Store handle
gHW = ListView1.hwnd
Hook
End Sub

Private Sub Form_Unload(Cancel As Integer)
'Pressing the End button or selecting End from _
the Run menu without unhooking causes _
an Invalid Page Fault and closes Microsoft Visual Basic.
'Call procedure to stop intercepting
'the messages for this window
Unhook
End Sub

End Form Code
'=============================

'-------
galen

: My application uses the ListView control and allows users to drag column
: headers and change their width. Of course the user wants these changes saved
: so every time I show a different list (with different column headers) I save
: the width and order of all columns.
:
: Most users will drag the columns just a few times and will then leave them
: alone. So 99 of a 100 times I'm saving the information for nothing.
:
: Does anybody know how to detect changes in columnheader position and width
: so I can save them only when needed?
:
: Roel de Regt
:
:
: