5 replies to this topic

[Captacha]

In my code the WM_COMMAND segment causes my program to exit when I click on a button. Why is this? Shouldn't it do nothing?

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wparam, LPARAM lparam)
{
switch(msg)
{
case WM_CREATE:
  CreateWindow("button", "Button 1", WS_VISIBLE | WS_CHILD, (width/2)-40, (height/2)-12, 80, 25, hwnd, (HMENU)1, NULL, NULL);
  CreateWindow("button", "Button 2", WS_VISIBLE | WS_CHILD, (width/2)-40, ((height/2)-12)-45, 80, 25, hwnd, (HMENU)2, NULL, NULL);
  break;
case WM_COMMAND:
  if(LOWORD(wparam) == 1)
  {
  }
case WM_CLOSE:
  DestroyWindow(hwnd);
  break;
case WM_DESTROY:
  PostQuitMessage(0);
  break;
default:
  return DefWindowProc(hwnd, msg, wparam, lparam);
  break;
}
}

[ApochPiQ]

You seem to have left out a break; just above case WM_CLOSE.

[Endurion]

Not the problem here, but you don't return anything for any handled message. In most cases you also want to call DefWindowProc for handled messages.

[dilyan_rusev]

And also you should return 0 for handled messages. I don't know if this is the full code, but I can't see a "return 0" statement. Returning 0 is important.

[Endurion]

And also you should return 0 for handled messages. I don't know if this is the full code, but I can't see a "return 0" statement. Returning 0 is important.

You cannot generally return 0. Look up the handled message and see what you should return (if you should do so).

[SiCrane]

In particular, a common mistake is to return 0 from WM_NCCREATE, which indicates that window creation shouldn't proceed and causes CreateWindow()/CreateWindowEx() to return a NULL handle. Confusingly, WM_CREATE does the opposite: 0 indicates success.