Determine which control a message came from

I have a dialog with several checkboxes. The code that is executed when one of the checkboxes is clicked is very similar for all checkboxes. I would like to be able to set the ON_BN_CLICKED macro for all my checkboxes to execute the same function then determine from which checkbox the message came.
Does anyone know of a way to determine what control a message came from?

Take a look at the Windows Programming Reference, the part about buttons/notification messages:

Code:

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When the user selects a button, its state changes, and the button sends notification messages to its parent window. For example, a push button control sends the BN_CLICKED notification message whenever the user chooses the button. In all cases, the low-order word of the wParam parameter contains the control identifier, the high-order word of wParam contains the notification code, and the lParam parameter contains the control window handle.

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Also take a look at how BM_CLICKED message is sent:

Code:

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The parent window of the button receives this notification message through the WM_COMMAND message.

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So just get the WM_COMMAND message and search for a HIWORD(wParam) that matches BN_CLICKED; there you will have the checkbox id as LOWORD(wParam) and the checkbox handle as lParam

Hope that helps

The LOWORD(wParam) will only be vaild if the child control had the HMENU param set (to an ID number) when it was created (or the control was created using a resource editor that stores a list of ID numbers in resource.h).

Code:

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case WM_COMMAND:

int CtrlID = LOWORD(wParam);

switch (CtrlID)
{
    case CB_NUM1:
    case CB_NUM2:
    .....
    case CB_NUMX:
        if(HIWORD(wParam) == BN_CLICKED)
        {
              return  DoCBProcessing(CtrlID);//handler determines return to OS
        }
    break;

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Quote:

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Originally Posted by roakes499

I have a dialog with several checkboxes. The code that is executed when one of the checkboxes is clicked is very similar for all checkboxes. I would like to be able to set the ON_BN_CLICKED macro for all my checkboxes to execute the same function then determine from which checkbox the message came.
Does anyone know of a way to determine what control a message came from?

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Here's a section of the resource file that creates a dialog box...

Code:

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SETUP0 DIALOGEX DISCARDABLE 8, 18, 299, 178
STYLE DS_SHELLFONT|WS_CHILD|WS_VISIBLE
EXSTYLE WS_EX_CONTROLPARENT|WS_EX_TOPMOST
FONT 8, "Tahoma", 0, 0, 1
{
  CONTROL "", 4001, "ListBox", LBS_MULTIPLESEL|LBS_SORT|LBS_NOINTEGRALHEIGHT|LBS_NOTIFY|WS_VSCROLL|WS_BORDER|WS_TABSTOP, 22, 19, 256, 44
  CONTROL "Add", 4002, "Button", BS_FLAT|WS_TABSTOP, 22, 65, 50, 14
  CONTROL "Remove", 4003, "Button", BS_FLAT|WS_TABSTOP, 92, 65, 50, 14
  CONTROL "Clear", 4004, "Button", BS_FLAT|WS_TABSTOP, 228, 65, 50, 14
  CONTROL "", 4005, "ListBox", LBS_MULTIPLESEL|LBS_SORT|LBS_NOINTEGRALHEIGHT|LBS_NOTIFY|WS_VSCROLL|WS_BORDER|WS_TABSTOP, 22, 107, 256, 44
  CONTROL "Add", 4006, "Button", BS_FLAT|WS_TABSTOP, 22, 153, 50, 14
  CONTROL "Remove", 4007, "Button", BS_FLAT|WS_TABSTOP, 92, 153, 50, 14
  CONTROL "Clear", 4008, "Button", BS_FLAT|WS_TABSTOP, 228, 153, 50, 14
  CONTROL " VC++  Program paths for X86 ", 4050, "Button", BS_GROUPBOX, 12, 7, 275, 79, WS_EX_TRANSPARENT
  CONTROL " VC++ Program paths for X64 ", 4051, "Button", BS_GROUPBOX, 12, 94, 275, 79
}

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See all the numbers starting with 4001 ... 4051 ... those are control ID numbers that are passed to message tosser in the lowword of the WM_COMMAND message's WPARAM. So you need to

Code:

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switch (LOWORD(wParam))
  case ...

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As Novacain has already explained.