winapiautohotkeywindows-messages

How to use SendMessage pass a WM_COMMAND with hwnd?

I got a WM_COMMAND in a button event by Spy++, It looks like:

image

<000116> 001B0A02 S WM_NOTIFY idCtrl:133978 pnmh:0019F9A0
<000117> 001B0A02 R WM_NOTIFY
<000118> 001B0A02 S WM_COMMAND wNotifyCode:0000 wID:2 hwndCtl:00020B5A
<000119> 001B0A02 R WM_COMMAND
<000120> 001B0A02 S WM_NOTIFY idCtrl:133978 pnmh:0019F9BC
<000121> 001B0A02 R WM_NOTIFY

Then I tried to redo WM_COMMAND by SendMessage:

image

Nothing happened. I used the AHK script to be sure, same result.

When I used SendMessage(), Spy++ got this:

<000423> 001B0A02 S WM_COMMAND wNotifyCode:0000 wID:2 hwndCtl:00000014
<000424> 001B0A02 R WM_COMMAND

I also let the lParam = 0, then it worked but not as I expected, another Menu item opened.

<000001> 001B0A02 S WM_COMMAND wNotifyCode:0 (sent from a menu) wID:2

So how can I do this?

Solution

  • To emulate the WM_COMMAND for a button click, you need to send the ID of your button and the BN_CLICKED notification code (combined) as the wParam argument to SendMessage(), and the handle (HWND) of the button as the lParam.

    If hDlg is the handle of your dialog window, and IDC_MYBUTTON is the resource ID of your button, the call would be like this:

    SendMessage(hDlg, WM_COMMAND, MAKEWPARAM(IDC_MYBUTTON, BN_CLICKED), (LPARAM)GetDlgItem(hDlg, IDC_MYBUTTON));

    As it happens, the BN_CLICKED notification code has a value of 0, so the wParam value will be just the control ID; this appears to be 2 in your case – the value used by Windows for the "Cancel" button. The problem, in your code, seems to be an invalid window handle for the lParam argument.