Why doesn't my window get WM_SIZE command when handling WM_KEYDOWN myself?

Question

I am unable to get WM_SIZE command if i use this method (or WM_KEYUP with same return 0 in end):

case WM_KEYDOWN: {
    keys[wParam] = 1;
    return 0;
}

But it gives me WM_SIZE command when i use this:

case WM_KEYDOWN: {
    keys[wParam] = 1;
    break;
}

Could someone explain why is this happening?

Answer 1

在没有看到整个代码的情况下，我的猜测是return语句阻止WM_KEYDOWN消息被传递给默认的消息处理程序，例如DefWindowProc() ，因此窗口实际上不会处理键击并采取它需要生成的任何操作WM_KEYUP和WM_SIZE消息。