Announcement

**Chris Boss** · 16 Apr 2009, 03:50 PM

Keyboard messages are sent to an applications message que and not directly to the window procedure of the window/control with the focus.

The message loop then forwards the message to the controls (TranslateMessage).

To process the messages to controls can be done in a number of ways.

(1) Subclass each control and then process the WM_KEYUP, WM_KEYDOWN and WM_CHAR messages

(2) Trap the keyboard messages in the message loop before they are sent to the controls. This allows you to access all the keyboard messages to all the controls, without subclassing.

(3) use a hook procedure to hook into all the windows keyboard messages.

Normally with DDT, you let DDT handle the message loop, so with DDT you would have to use a custom message loop to preprocess messages in the message loop.

With DDT, I think a good approach would be to write a universal subclassing routine. Create a subroutine which can subclass any control you like. That routine would subclass the control sending all its window procedure messages to a single universal subclass window procedure. Store the original window procedure address in a window property and use the API property functions to retrieve the appropriate window procedure address for each control. Define a couple user messages (%WM_USER + #) which can be used for forwarding the messages. In the WM_KEYUP, WM_KEYDOWN and WM_CHAR messages in the subclass window procedure, forward the messages (using your custom user messages) to the parent dialog. This would allow you to handle all your keyboard processing in the parent dialogs dialog procedure for all the controls on the dialog, rather than have a separate routine for each control.

**John Gleason** · 16 Apr 2009, 04:36 PM

(2) Trap the keyboard messages in the message loop before they are sent to the controls. This allows you to access all the keyboard messages to all the controls, without subclassing.

Thanks Chris, this sounds like the best choice in my case, but I don't know about hooks, so that could be a contender too. Can I trap the keyboard messages and still have DDT style programming? I'll check around for custom message loop preprocessing in poffs etc. The universal routine, with atom fcns sounds excellent, tho I think may be beyond my grasp at this juncture.

**Eddy Van Esch** · 16 Apr 2009, 05:29 PM

John,

The most versatile way would be to use a global keyboard hook:
Here's one example by Paul Dixon but there is more to be found on these forums.

Kind regards

**Chris Boss** · 16 Apr 2009, 05:55 PM

I am not sure how much stuff DDT does in the message loop, so it is hard to say if there is a downside to using your own message loop, rather than the standard DDT Dialog DoEvents loop.

The other problem is that you can't have your own custom message loop for Modal dialogs.

I think the subclass method may be best for DDT.

Here is an example of using subclassing to trap keyboard messages which are forwarded to the parent dialog:

Code:

' ***************************************************************
'   This code can be used Royalty Free and Freely Distributed !
' ***************************************************************
#COMPILE EXE
#REGISTER NONE
#DIM ALL          '  This is helpful to prevent errors in coding
 
#INCLUDE "win32api.inc"   ' Must come first before other include files !
' *************************************************************
'                  Constants and Declares (#1)
' *************************************************************
%FORM1_LABEL1             = 100
%FORM1_BUTTON1            = 105
%FORM1_BUTTON2            = 110
%FORM1_TEXT1              = 115
%FORM1_LISTBOX1           = 120
' --------------------------------------------------
DECLARE SUB ShowDialog_Form1(BYVAL hParent&)
DECLARE CALLBACK FUNCTION Form1_DLGPROC
' --------------------------------------------------
DECLARE CALLBACK FUNCTION CBF_FORM1_BUTTON1()
DECLARE CALLBACK FUNCTION CBF_FORM1_BUTTON2()
DECLARE CALLBACK FUNCTION CBF_FORM1_TEXT1()
DECLARE CALLBACK FUNCTION CBF_FORM1_LISTBOX1()
'
' *************************************************************
'               Application Globals Variables (#2)
' *************************************************************
'
GLOBAL hForm1&    ' Dialog handle
%App_KeyMessage     =    %WM_USER+400
TYPE AppKey
     KMsg AS LONG
     KhCtrl AS LONG
     KCtrlID AS LONG
     KwParam AS LONG
     KlParam AS LONG
END TYPE
'
' *************************************************************
'                    Application Entrance
' *************************************************************
'
FUNCTION PBMAIN
    LOCAL Count&
    ShowDialog_Form1 0
    DO
        DIALOG DOEVENTS TO Count&
    LOOP UNTIL Count&=0
    MakeKeySubClass 0,0  ' clears subclass atoms
END FUNCTION
'
' *************************************************************
'                    Application Dialogs (#3)
' *************************************************************
'
SUB ShowDialog_Form1(BYVAL hParent&)
    LOCAL Style&, ExStyle&
    LOCAL N&, CT&        '  Variables used for Reading Data in Arrays for Listbox and Combobox
    '   hParent& = 0 if no parent Dialog
    Style& = %WS_POPUP OR %DS_MODALFRAME OR %WS_CAPTION OR %WS_MINIMIZEBOX OR %WS_SYSMENU OR %DS_CENTER
    ExStyle& = 0
    DIALOG NEW hParent&, "Your Dialog", 0, 0,  267,  177, Style&, ExStyle& TO hForm1&
    CONTROL ADD LABEL, hForm1&,  %FORM1_LABEL1,  "Label  1", 40, 153, 192, 12, _
        %WS_CHILD OR %WS_VISIBLE OR %SS_CENTER OR %WS_BORDER
    CONTROL ADD "Button", hForm1&,  %FORM1_BUTTON1,  "Button  1", 29, 20, 53, 15, _
        %WS_CHILD OR %WS_VISIBLE OR %BS_PUSHBUTTON OR %WS_TABSTOP CALL CBF_FORM1_BUTTON1
    MakeKeySubClass hForm1&,%FORM1_BUTTON1
    CONTROL ADD "Button", hForm1&,  %FORM1_BUTTON2,  "Button  2", 29, 49, 53, 15, _
        %WS_CHILD OR %WS_VISIBLE OR %BS_PUSHBUTTON OR %WS_TABSTOP CALL CBF_FORM1_BUTTON2
    MakeKeySubClass hForm1&,%FORM1_BUTTON2
    CONTROL ADD TEXTBOX, hForm1&,  %FORM1_TEXT1,  "", 93, 20, 83, 47, _
        %WS_CHILD OR %WS_VISIBLE OR %ES_MULTILINE OR %ES_WANTRETURN OR %ES_LEFT OR %WS_TABSTOP, _
        %WS_EX_CLIENTEDGE CALL CBF_FORM1_TEXT1
    MakeKeySubClass hForm1&,%FORM1_TEXT1
    ' - - - - - - - - - - - - - - - - - - - - - - - - -
    DIM LISTBOX1_List(4) AS LOCAL STRING
    DATA "Item 1","Item 2","Item 3","Item 4","Item 5"
    FOR N&=0 TO 4
        CT&=CT&+1
        LISTBOX1_List(N&)=READ$(CT&)
    NEXT N&
    ' - - - - - - - - - - - - - - - - - - - - - - - - -
    CONTROL ADD LISTBOX, hForm1&,  %FORM1_LISTBOX1, LISTBOX1_List(), 187, 17, 53, 52, _
        %WS_CHILD OR %WS_VISIBLE OR %LBS_NOTIFY OR %LBS_SORT OR %LBS_NOINTEGRALHEIGHT OR %WS_VSCROLL OR %WS_TABSTOP, _
        %WS_EX_CLIENTEDGE CALL CBF_FORM1_LISTBOX1
    MakeKeySubClass hForm1&,%FORM1_LISTBOX1
    DIALOG SHOW MODELESS hForm1& , CALL Form1_DLGPROC
END SUB
'
' *************************************************************
'                             Dialog Callback Procedure
'                             for Form Form1
'                             uses Global Handle - hForm1&
' *************************************************************
'
CALLBACK FUNCTION Form1_DLGPROC
    SELECT CASE CBMSG
        CASE %App_KeyMessage
             LOCAL K AS AppKey PTR, T$
             K=CBWPARAM
             SELECT CASE @K.KMsg
                  CASE %WM_KEYUP
                       T$="WM_KEYUP"
                  CASE %WM_KEYDOWN
                       T$="WM_KEYDOWN"
                  CASE %WM_CHAR
                       T$="WM_CHAR"
                  CASE ELSE
                       T$=""
             END SELECT
             IF T$<>"" THEN
                  T$=T$+" "+STR$(@K.KCtrlID)+"    "+STR$(@K.KwParam)+" , "+STR$(@K.KlParam)
             END IF
             CONTROL SET TEXT hForm1&,%FORM1_LABEL1, T$
             EXIT FUNCTION
        CASE ELSE
    END SELECT
END FUNCTION
'
' *************************************************************
'   Application Callback Functions (or Subs) for Controls (#4)
' *************************************************************
'
CALLBACK FUNCTION CBF_FORM1_BUTTON1
    IF CBCTLMSG=%BN_CLICKED THEN
    END IF
END FUNCTION
' ------------------------------------------------
'
CALLBACK FUNCTION CBF_FORM1_BUTTON2
    IF CBCTLMSG=%BN_CLICKED THEN
    END IF
END FUNCTION
' ------------------------------------------------
'
CALLBACK FUNCTION CBF_FORM1_TEXT1
    IF CBCTLMSG=%EN_CHANGE THEN
    END IF
END FUNCTION
' ------------------------------------------------
'
CALLBACK FUNCTION CBF_FORM1_LISTBOX1
    LOCAL CVal&
    ' Return Current Selection in CVal&
    CONTROL SEND CBHNDL , CBCTL, %LB_GETCURSEL, 0,0 TO CVal&
    IF CBCTLMSG=%LBN_SELCHANGE THEN
    END IF
END FUNCTION
'
GLOBAL App_OriginalWinProcAtom&
'
SUB MakeKeySubClass(BYVAL hDlg&, BYVAL ID&)
     LOCAL T AS ASCIIZ*256, hCtrl&, WA&
     STATIC AFlag&
     IF AFlag&=0 THEN
          AFlag&=1
          T="origwinproc"
          App_OriginalWinProcAtom&=GlobalAddAtom(T)
     END IF
     IF hDlg&=0 AND ID&=0 THEN
          AFlag&=0
          IF App_OriginalWinProcAtom&<>0 THEN GlobalDeleteAtom App_OriginalWinProcAtom&
     END IF
     hCtrl&=GetDlgitem(hDlg&, ID&)
     IF hCtrl&<>0 THEN
          WA&=SetWindowLong(hCtrl&, %GWL_WNDPROC, BYVAL CODEPTR(KeySubClassProc))
          SetProp hCtrl&, BYVAL MAKLNG(App_OriginalWinProcAtom&,0), WA&
     END IF
END SUB
'
FUNCTION KeySubClassProc(BYVAL hWnd&, BYVAL Msg&, BYVAL wParam&, BYVAL lParam&) AS LONG
     LOCAL WA&
     WA&=GetProp(hWnd&, BYVAL MAKLNG(App_OriginalWinProcAtom&,0))
     SELECT CASE Msg&
          CASE %WM_KEYUP, %WM_KEYDOWN, %WM_CHAR
               LOCAL K AS AppKey
               K.KMsg = Msg&
               K.KhCtrl = hWnd&
               K.KCtrlID = GetDlgCtrlID(hWnd&)
               K.KwParam = wParam&
               K.KlParam = lParam&
               IF SendMessage(GetParent(hWnd&), %App_KeyMessage , VARPTR(K),0)<>0 THEN
                    FUNCTION=0
                    EXIT FUNCTION  ' prevent default processing
               END IF
          CASE %WM_DESTROY
               SetWindowLong hWnd&, %GWL_WNDPROC, WA&
               RemoveProp hWnd&, BYVAL MAKLNG(App_OriginalWinProcAtom&,0)
     END SELECT
     FUNCTION=CallWindowProc(WA&, hWnd&, Msg&, wParam&, lParam&)
END FUNCTION

**John Gleason** · 16 Apr 2009, 06:19 PM

Thanks Eddy for the link, I'll look at that.

Thanks Chris for the code, I'll check it out & compile it now.

**Michael Mattias** · 16 Apr 2009, 06:52 PM

AS long as you are just getting started with this key-press thing...

You probably want to look at doing whatever it is you are going to do on the WM_KEYUP notification rather than the WM_KEYDOWN.

The reason being, if the user holds the key down, you can get multiple keydown notrifications when the keyboard repeat thing kicks in.. and you only ever get one "key up" notification.

**John Gleason** · 17 Apr 2009, 08:23 AM

Thanks Chris for the informational tour de force. It demos much in a concise package.

I think I'll be able to incorporate the code pretty quickly, and possibly even understand how it works in a couple da... we... months.

I'm a thanking you for that, really.

Thanks too Eddy for the hook link, which may come in handy at some point.

And thanks MCM for the tip. I'll need handle those events.

**Cliff Nichols** · 17 Apr 2009, 07:12 PM

AS long as you are just getting started with this key-press thing...

You probably want to look at doing whatever it is you are going to do on the WM_KEYUP notification rather than the WM_KEYDOWN.

The reason being, if the user holds the key down, you can get multiple keydown notrifications when the keyboard repeat thing kicks in.. and you only ever get one "key up" notification.

MCM I am on the exact OPPOSITE side of that note (Heh...Imagine that

)

In my limited experience (limited as in not having researched just the WHYYYyyy??? but the idea that it happens), the %KEYUP can be missed. So I use %KEYDOWN (since it is what initiates the whole process to begin with)

That way the process is not missed at all (or at least in my experience) and if it is...then programmer error.

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