Over-ride the events of a control.

Hi VB Gurus,
I want to have a generic implementation of an application and hence I want to override some of the events of a TextBox control. Can any of you provide me with some input on this. Thanking you in advance.
Saju

You can do this by subclassing the control. What this basically means is intercepting the messages sent to the textbox and overriding them - if you tell me what events you want to override I'll be able to give you more info.

HTH,
Duncan

-------------------------------------------------
Ex. Datis: Duncan Jones
Merrion Computing Ltd
http://www.merrioncomputing.com

I need to override the click event of a Command Button Control and also to override the lostfocus event of a TextBox Control. It would be real helpful if you could provide me with some more information. Thanks a lot in advance.
Saju

When a command button receives a WM_LBUTTONDOWN message followed by a WM_LBUTTONUP message it generates a Click() event. If you don't want the button to go down, intercept the WM_LBUTTONDOWN message and don't allow it to be processed by the button.

When a textbox is about to lose the input focus it recieves a WM_KILLFOCUS message. You can respond to this by calling the SetFocus() routine to set focus back to the textbox.

Subclassing is a very powerful but also very difficult technique to use. Fortunately there is a dll called the EventVB.dll that we have created that will (hopefully) assist you greatly. It can be downloaded from http://www.merrioncomputing.com/Download/index.htm.

To use it, the following code is required:

'\\ Form declarations
Dim withevents ApiLink as EventVB.ApiFunctions
Dim withevents wndCommand as EventVB.ApiWindow
Dim withevents wndTextbox as EventVB.ApiWindow

'\\ Form load
private Sub Form_Load()
set ApiLink = new EventVB.ApiFunctions
set wndCommand = new EventVB.ApiWindow
set wndTextBox = new EventVB.ApiWindow

'\\ Connect the wnd Variables to the actual controls
wndTextBox.hwnd = Text1.hwnd
wndCommand.hwnd = Command1.hwnd

'\\ Start subclassing the events...
ApiLink.SubclassedWindows.Add wndTextBox
ApiLink.SubclassedWindows.Add wndCommand

End Sub

'\\ Form queryunload
private Sub Form_QueryUnload(Cancel as Integer, UnloadMode as Integer)
'\\ Stop subclassing the windows
ApiLink.SubclassedWindows.Remove wndTextBox
ApiLink.SubclassedWindows.Remove wndCommand
End Sub

'\\ Form terminate
private Sub Form_Terminate()
'\\ Free the object variables....
set wndTextbox = nothing
set wndCommand = nothing
set ApiLink = nothing
End Sub

'\\ Commandbutton window message
private Sub wndCommand_WindowMessageFired(byval msg as WindowMessages, byval wParam as Long, byval lParam as Long, Cancel as Boolean, ProcRet as Long)

If msg = WM_LBUTTONDOWN then
'\\ Discard the message
Cancel = true
End If'\\ Textbox window message
private Sub wndTextbox_WindowMessageFired(byval msg as WindowMessages, byval wParam as Long, byval lParam as Long, Cancel as Boolean, ProcRet as Long)

If msg = WM_KILLFOCUS then
Text1.SetFocus
End If

End Sub




HTH,
End Sub


Duncan

-------------------------------------------------
Ex. Datis: Duncan Jones
Merrion Computing Ltd
http://www.merrioncomputing.com