[SOLVE]How to use the fifth parameter in SetWindowCallback()

[avatar]

From the manual, it is allowed to optionally set the fifth window call back parameter "#Window"

SetWindowCallback(@ProcedureName() [, #Window])

How can I retrieve this information from the Call back function?

Code: Select all

  Procedure WinCallback(hWnd, uMsg, wParam, lParam) 
    debug str(#Window) ; <----------------------------------- ERROR
    If uMsg = #WM_SIZE 
      Select wParam 
        Case #SIZE_MINIMIZED 
          Debug "Window was minimized" 
        Case #SIZE_RESTORED 
          Debug "Window was restored" 
        Case #SIZE_MAXIMIZED 
          Debug "Window was maximized" 
      EndSelect 
    EndIf 
    ProcedureReturn #PB_ProcessPureBasicEvents 
  EndProcedure 
  If OpenWindow(123, 0, 0, 200, 100, "Messages", #PB_Window_MinimizeGadget|#PB_Window_MaximizeGadget) 
    SetWindowCallback(@WinCallback(),123)    ; activate the callback
    Repeat 
      Select WaitWindowEvent() 
        Case #PB_Event_CloseWindow 
          End 
      EndSelect 
    ForEver 
  EndIf 

[idle]

you need to use the hwnd of the window number

Code: Select all

Procedure WinCallback(hWnd, uMsg, wParam, lParam)
  
    Debug Str(hwnd) ; your window is the hwnd 
    If uMsg = #WM_SIZE
      Select wParam
        Case #SIZE_MINIMIZED
          Debug "Window was minimized"
        Case #SIZE_RESTORED
          Debug "Window was restored"
        Case #SIZE_MAXIMIZED
          Debug "Window was maximized"
      EndSelect
    EndIf
    ProcedureReturn #PB_ProcessPureBasicEvents
  EndProcedure
  
  If OpenWindow(123, 0, 0, 200, 100, "Messages", #PB_Window_MinimizeGadget|#PB_Window_MaximizeGadget)
    hwnd = WindowID(123) ;get the hwnd for the window 
    Debug "Window handle=" + Str(hwnd) 
    SetWindowCallback(@WinCallback(),123) ; activate the callback for the window number 123
    ;it uses the windowID / hwnd for processing in the callback 
    Repeat
      Select WaitWindowEvent()
        Case #PB_Event_CloseWindow
          End
      EndSelect
    ForEver
  EndIf 

[avatar]

Thank for the help

[netmaestro]

There are a maximum of two parameters to the SetWindowCallback() function. The first is a code pointer, the address of a procedure that you designate to function as a Window Callback. The OS will call this procedure, passing it every message that is intended for the window. That procedure always has four parameters: handle, message, wparam and lparam. Handle is the hWnd, message is the Windows message, and WParam is a four-byte value often consisting of two WORD values, one high-order and one low-order. Hence the name wParam (word-parameter). LParam is usually one LONG value, hence the name lParam. The fact that Windows will often pass one LONG in wParam and two WORDs in lparam shouldn't serve to confuse you; that's just their schizophrenia talking. Probably brought about by all the caffeine in those free sodas at the MS compound. The optional second parameter in SetWindowCallback() is a window number, the one you specified when you created the window (or the one returned to you by #PB_Any if you went that route). You only pass this if you have several windows in your program, any of which may be active at any given time, and you want the callback only set up for a specific window. Ignoring the others, yes. But so what? Scr** them. What have those windows ever done for you?

[avatar]

Thanks netmeastro for the detailed explanation.

Yes, I want to have more than one window opened.

The window ID (in my example, 123) can be very helpful if I can identify it within the call back procedure.

When I pass the fifth parameter to the call back procedure, how can I retrieve it from within the call back procedure?

[netmaestro]

how can I retrieve it from within the call back procedure?

If hwnd = WindowID(<number>)
.. [ ]
EndIf

But if you passed the optional #window parameter, you can be sure that the only hwnd dealt with in the callback will be the one you passed. Messages for the others won't go to the callback.

[avatar]

Thanks Bullfrog

I am thinking similar method as yours