Subject: Re: bug#37415: Asserting failure setting frame parameters to non-fixnum values in early-init.el

From: martin rudalics <[email-masked]>
Date: Sun, 22 Sep 2019 10:08:53 +0200

>> Before 572fe798cd0a00ad4a9050a7962cf8e8fbcc209b (from 2014-09-30), the computation of left and top
 >> was done in w32_createwindow:
 >>
 >>        /* When called with RES_TYPE_NUMBER, w32_get_arg will return zero
 >>          for anything that is not a number and is not Qunbound.  */
 >>        left = x_get_arg (dpyinfo, Qnil, Qleft, "left", "Left", RES_TYPE_NUMBER);
 >>        top = x_get_arg (dpyinfo, Qnil, Qtop, "top", "Top", RES_TYPE_NUMBER);
 >>
 >> and anything not a number was turned to 0.
 >>
 >> In that commit you moved the code to my_create_window and used XINT:
 >>
 >>   +  /* When called with RES_TYPE_NUMBER, x_get_arg will return zero for
 >>   +     anything that is not a number and is not Qunbound.  */
 >>   +  left = x_get_arg (dpyinfo, Qnil, Qleft, "left", "Left", RES_TYPE_NUMBER);
 >>   +  top = x_get_arg (dpyinfo, Qnil, Qtop, "top", "Top", RES_TYPE_NUMBER);
 >>   +  if (EQ (left, Qunbound))
 >>   +    coords[0] = CW_USEDEFAULT;
 >>   +  else
 >>   +    coords[0] = XINT (left);
 >>   +  if (EQ (top, Qunbound))
 >>   +    coords[1] = CW_USEDEFAULT;
 >>   +  else
 >>   +    coords[1] = XINT (top);
 >>   +
 >
 > Yes, but contrary to the comment, in the case in point we don't get
 > zero from x_get_arg.  Which is why I asked all those questions.

Well, now you really asked it ...

When called with PARAM Qleft and ALIST Qnil x_get_arg

{
   Lisp_Object tem;

   tem = Fassq (param, alist);

   if (!NILP (tem))
     ...
	  XSETCAR (XCAR (tail), Qnil);
     }
   else
     tem = Fassq (param, Vdefault_frame_alist);

   if (NILP (tem))
     ...

   return Fcdr (tem);
}

returns the cdr of the 'default-frame-alist' entry for 'left' which
can be anything.  So that comment is wrong and using x_get_arg here
probably too.  Any reason why we cannot just use f->left_pos

my_create_window (struct frame * f)
{
   MSG msg;
   static int coords[2];

   coords[0] = f->left_pos;
   coords[1] = f->top_pos;
   if (!PostThreadMessage (dwWindowsThreadId, WM_EMACS_CREATEWINDOW,
			  (WPARAM)f, (LPARAM)coords))
     emacs_abort ();
   GetMessage (&msg, NULL, WM_EMACS_DONE, WM_EMACS_DONE);
}

like the X build does?

martin