DO declare
 
LOCAL oForm As Tform
oForm=CREATEOBJECT("Tform")
oForm.Show()
READ EVENTS
* end of main
 
DEFINE CLASS Tform As Form
#DEFINE WM_PARENTNOTIFY 0x0210
#DEFINE WM_COMMAND 0x0111
#DEFINE WM_LBUTTONDOWN 0x201
#DEFINE WM_RBUTTONDOWN 0x204
#DEFINE GWL_WNDPROC -4
PROTECTED hWindow, hOrigProc
    hWindow=0
    hOrigProc=0
    Caption = "Adding the Windows Button to the form"
    Height = 250
    Width = 450
    Autocenter = .T.
    hButton = 0
 
    ADD OBJECT chAddButton As CheckBox WITH;
    Left=20, Top=20, Autosize=.T., Caption="Add Button"
 
PROCEDURE Destroy
    THIS.RemoveButton
    CLEAR EVENTS
 
PROCEDURE Activate
    IF THIS.hWindow = 0
        THIS.hWindow = GetFocus()
        THIS.hOrigProc = GetWindowLong(THIS.hWindow, GWL_WNDPROC)
 
        * link WM_PARENTNOTIFY window message to a method
        IF VERSION(5) >= 900
            = BINDEVENT(THIS.hWindow, WM_PARENTNOTIFY, THIS, "WindowProc")
            = BINDEVENT(THIS.hWindow, WM_COMMAND, THIS, "WindowProc")
        ENDIF
    ENDIF
 
PROCEDURE RemoveButton
    IF DestroyWindow(THIS.hButton) <> 0
        THIS.hButton = 0
    ENDIF
 
PROCEDURE AddButton
#DEFINE GWL_HINSTANCE -6
#DEFINE BS_DEFPUSHBUTTON 1
#DEFINE BS_PUSHBUTTON 0
#DEFINE BS_OWNERDRAW 0x000b
#DEFINE WS_VISIBLE 0x10000000
#DEFINE WS_CHILD 0x40000000
 
    LOCAL hApp, hParentHWnd, lnStyle, lnStyleX,;
        lnX, lnY, lnWidth, lnHeight
 
*    lnStyle = WS_VISIBLE+WS_CHILD+BS_PUSHBUTTON)
    lnStyle = BITOR(WS_VISIBLE, WS_CHILD, BS_PUSHBUTTON)
    lnStyleX = 0
 
    * handle to the window hosting the button
*    hParentHWnd=GetFocus()
    hParentHWnd=ThisForm.HWnd  && will not work for ShowWindow=2
 
    * handle to application instance
    hApp = GetWindowLong(hParentHWnd, GWL_HINSTANCE)
 
    * unique child-window identifier
    lnId = VAL(SYS(3))
 
    * size and position
    lnX = 140
    lnY = 50
    lnWidth = 100 
    lnHeight = 28
 
    * the predefined control class BUTTON is used 
    THIS.hButton = CreateWindow (lnStyleX, "BUTTON",;
        "True &Button", lnStyle,;
        lnX, lnY, lnWidth, lnHeight,;
        hParentHWnd, lnId, hApp, 0)
 
PROTECTED PROCEDURE WindowProc(hWindow as Integer,;
    nMsgID as Integer, wParam as Integer, lParam as Integer)
* requires VFP9, otherwise ignored
 
    LOCAL nReturn
    nReturn=0
 
    DO CASE
    CASE nMsgID=WM_COMMAND
        ACTIVATE SCREEN
        ? "WM_COMMAND: wParam=" + LTRIM(STR(wParam)) +;
            ", lParam=" + LTRIM(STR(lParam))
 
    CASE nMsgID=WM_PARENTNOTIFY
        ACTIVATE SCREEN
        ? "WM_PARENTNOTIFY: wParam=" + LTRIM(STR(wParam)) +;
            ", lParam=" + LTRIM(STR(lParam))
 
        DO CASE
        CASE wParam=WM_LBUTTONDOWN
            ?? " -- Left Button pressed"
        CASE wParam=WM_RBUTTONDOWN
            ?? " -- Right Button pressed"
        ENDCASE
 
    OTHERWISE
    * pass control to the original window procedure
        nReturn = CallWindowProc(THIS.hOrigProc, THIS.hWindow,;
            m.nMsgID, m.wParam, m.lParam)
    ENDCASE
RETURN nReturn
 
PROCEDURE chAddButton.Click
    IF ThisForm.hButton=0
        ThisForm.AddButton
    ELSE
        ThisForm.RemoveButton
    ENDIF
    THIS.Caption = IIF(ThisForm.hButton=0,;
        "Add Button", "Remove Button")
 
ENDDEFINE
 
PROCEDURE declare
    DECLARE INTEGER GetFocus IN user32
 
    DECLARE INTEGER DestroyWindow IN user32;
        INTEGER hWindow
 
    DECLARE INTEGER GetWindowLong IN user32;
        INTEGER hWnd, INTEGER nIndex
 
    DECLARE INTEGER CreateWindowEx IN user32 AS CreateWindow;
        INTEGER dwExStyle, STRING lpClassName,;
        STRING lpWindowName, INTEGER dwStyle,;
        INTEGER x, INTEGER y, INTEGER nWidth, INTEGER nHeight,;
        INTEGER hWndParent, INTEGER hMenu, INTEGER hInstance,;
        INTEGER lpParam