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Receiving Hotkeys

Posted on 1998-06-19
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Last Modified: 2010-05-03
With RegisterHotkey(...) a HotKey is registered.
But how can I receive notification, when the selected HotKey is pressed (anywhere in the system)?
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Question by:soeding1
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yowkee earned 100 total points
ID: 1463832
soeding1,

  When your application, you use RegisterHotkey to register a hotkey, then when the seleted hotkey is pressed, it will be send to your application a message WM_HOTKEY. Then your application must handle this message and do what you want to do. In VB this required subclassing of windows procedure.

  Here's an example to register hotkey Ctrl-1, when the hotkey pressed, restore the minimized form and set it focus.

---- Codes in a BAS module
Public Declare Function RegisterHotKey Lib "user32" (ByVal hwnd As Long, ByVal id As Long, ByVal fsModifiers As Long, ByVal vk As Long) As Long
Public Declare Function UnregisterHotKey Lib "user32" (ByVal hwnd As Long, ByVal id As Long) As Long
Public Declare Function GlobalAddAtom Lib "kernel32" Alias "GlobalAddAtomA" (ByVal lpString As String) As Integer
Public Declare Function GlobalDeleteAtom Lib "kernel32" (ByVal nAtom As Integer) As Integer
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
Declare Function SetWindowLong Lib "user32" Alias "SetWindowLongA" _
    (ByVal hwnd As Long, _
     ByVal nIndex As Long, _
     ByVal dwNewLong As Long) As Long
Declare Function BringWindowToTop Lib "user32" (ByVal hwnd As Long) As Long
Declare Function ShowWindow Lib "user32" (ByVal hwnd As Long, ByVal nCmdShow As Long) As Long
Declare Function SetFocus Lib "user32" (ByVal hwnd As Long) As Long
Declare Function SetForegroundWindow Lib "user32" (ByVal hwnd As Long) As Long

Public Const SW_NORMAL = 1
Public Const GWL_WNDPROC = -4
Public Const WM_HOTKEY = &H312
Public Const MOD_ALT = &H1
Public Const MOD_CONTROL = &H2
Public Const MOD_SHIFT = &H4

Public lpPrevWndProc As Long
Public AtomID As Integer

Public Sub SubClass(ByVal hwnd As Long)
    lpPrevWndProc = SetWindowLong(hwnd, GWL_WNDPROC, AddressOf WindowProc)
End Sub

Public Sub UnSubClass(ByVal hwnd As Long)
    Dim lngReturnValue As Long
    If lpPrevWndProc Then _
        Call SetWindowLong(hwnd, 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
       
    If uMsg = WM_HOTKEY Then
        Call ShowWindow(hwnd, SW_NORMAL)
        Call SetFocus(hwnd)
        Call SetForegroundWindow(hwnd)
    End If
    WindowProc = CallWindowProc(lpPrevWndProc, hwnd, uMsg, wParam, lParam)

End Function

----Code in Form module
Private Sub Form_Load()
     AtomID = GlobalAddAtom("Atom1")
     Call RegisterHotKey(hwnd, AtomID, MOD_CONTROL, vbKey1)
     SubClass Me.hwnd
End Sub
Private Sub Form_QueryUnload(Cancel As Integer, UnloadMode As Integer)
    UnSubClass Me.hwnd
    Call UnregisterHotKey(hwnd, AtomID)
    Call GlobalDeleteAtom(AtomID)
End Sub

-----

Remember to unregister the hotkey and delete the added atom when application exit.

Regards.

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Author Comment

by:soeding1
ID: 1463833
Thank you, yowkee.
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