Keydown not working using [Message Structure]

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So I'm trying to get to process the keydown message while starting my application

I already had some code that I used to prevent the window from being moved or resized ..

Looking at the Microsoft documentation it seemed to me I could easily expand my existing code
by testing for the correct message sent
below is my code:
The [case WM_NCLBUTTONDOWN ] works perfect - but my [Case WM_KEYDOWN] never enters ???

Protected Overrides Sub WndProc(ByRef m As System.Windows.Forms.Message)
        Const WM_KEYDOWN As Integer = &H100
        Const WM_NCLBUTTONDOWN As Integer = &HA1
        Const HT_CAPTION As Integer = &H2
        Select Case m.Msg

            Case WM_KEYDOWN
                MsgBox("key Pressed")

            Case WM_NCLBUTTONDOWN  'Locking window from resizing & moving
                If KDMStatus.LockWindow_Positions = True Then
                    If m.WParam = New IntPtr(HT_CAPTION) Then
                        Return
                    End If
                End If
        End Select


        MyBase.WndProc(m)
    End Sub

What am I missing ? Can I actually trapping the keydown events by using the Message Structure

Georg

Posted 7-Jun-13 9:30am

Georg Kohler

Updated 7-Jun-13 9:41am

v4

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Sergey Alexandrovich Kryukov 7-Jun-13 15:33pm

Tag it: "WinForms".
—SA

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Dave Kreskowiak · Accepted Answer · 2013-06-07T15:30:00

If you're talking about having a key held down when your app starts so you can do something special, the WM_KEYDOWN message won't help you. As a matter of fact, no messages wil help you.

The WM_KEYDOWN message is sent only when the key is "made", or goes down. It does not tell you that a key is being held down.

To check keystate you have to PInvoke GetKeyState[^] when your app starts. You can get the state of a few keys if you want. Each key will take a seperate call to GetKeyState.

Sergey Alexandrovich Kryukov · Accepted Answer · 2013-06-07T09:39:00

Preventing a form from resize is its standard option, please see:
http://msdn.microsoft.com/en-us/library/system.windows.forms.form.formborderstyle.aspx[^],
http://msdn.microsoft.com/en-us/library/hw8kes41.aspx[^].

Four System.Windows.Forms.FormBorderStyle.Fixed* members of this enumeration provide options with fixed size.

As to preventing a form to move, it would be a huge abuse and a crime against the freedom of your users! Just don't do it, ever.

Therefore, your problem is solved without directly messing with message handling.

[EDIT #1]

As to your question, I can explain what's the reason for not getting to the case WM_KEYDOWN, but you need to check it up with your code which I cannot see, otherwise it won't be 100% certain.

The thing is: you handle only the messages on your form, but you might also have some controls on your form. One of those controls can possess the keyboard focus. In this case, all keyboard events are handled in this control, so they don't reach your form.

For a test, try same code on empty form, then you will see.

[EDIT #2]

Now, the question is: what to do in practice? You could handle keyboard events on all of your focusable controls as well, but you don't need this complication.

And you don't really need to use WndProc to handle keyboard messages. All functionality you possibly can have with those messages, you can by handling some or all of the System.Windows.Forms.Control keyboard events: KeyDown, KeyUp, KeyPress and PreviewKeyDown:
http://msdn.microsoft.com/en-us/library/system.windows.forms.form.aspx[^].

You can handle any of these event in the form, without having the problem with a focused child control which can possess the keyboard focus. Now — attention! this is the key point: for this purpose, you should also assign true to the form property KeyPreview:
http://msdn.microsoft.com/en-us/library/system.windows.forms.form.keypreview.aspx[^].

I think, by now your question is comprehensively answered.

—SA

Keydown not working using [Message Structure]

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