There is a slightly cosmetic issue with above function. When one switches
back on decorations,
the frame will not resize properly and minibuffer will be not visible. It's
there but just
covered by frame. Just resizing emacs framefixes it.

Adding call to PostMessage(hwnd, WM_SIZE,0,0) in Martins function fixes it.

void
x_set_undecorated (struct frame *f, Lisp_Object new_value, Lisp_Object
old_value)
{
  HWND hwnd = FRAME_W32_WINDOW (f);
  DWORD dwStyle = GetWindowLong (hwnd, GWL_STYLE);
  /*Lisp_Object border_width = Fcdr (Fassq (Qborder_width,
f->param_alist));*/
  /*Lisp_Object undecorated = Fcdr (Fassq (Qundecorated, f->param_alist));*/

  block_input ();
  if (!NILP (new_value) && !FRAME_UNDECORATED (f))
    {
      dwStyle = (dwStyle & ~WS_THICKFRAME & ~WS_CAPTION);
      SetWindowLong (hwnd, GWL_STYLE, dwStyle);
      SetWindowPos (hwnd, HWND_TOP, 0, 0, 0, 0,
                    SWP_NOSIZE | SWP_NOMOVE | SWP_NOZORDER | SWP_NOACTIVATE
                    | SWP_FRAMECHANGED);
      FRAME_UNDECORATED (f) = true;
    }
  else if (!NILP (new_value) && FRAME_UNDECORATED (f))
    {
      SetWindowLong (hwnd, GWL_STYLE, dwStyle | WS_THICKFRAME | WS_CAPTION
                     | WS_MAXIMIZEBOX | WS_MINIMIZEBOX | WS_SYSMENU);
      SetWindowPos (hwnd, HWND_TOP, 0, 0, 0, 0,
                    SWP_NOSIZE | SWP_NOMOVE | SWP_NOZORDER | SWP_NOACTIVATE
                    | SWP_FRAMECHANGED);
      PostMessage(hwnd, WM_SIZE,0,0);
      FRAME_UNDECORATED (f) = false;
    }
  unblock_input ();
}


2017-01-11 8:24 GMT+01:00 Arthur Miller <arthur.miller.no1@gmail.com>:

> I appologize, I was too fast to answer, I made a bad call from
> modify-frame-parameters
> when I tested it. It works like a charm as you say it in english. I have
> also changed
> the else-if statement in Martins method to else if (!NILP (new_value) &&
> FRAME_UNDECORATED (f))
> (check for !NILP) so I can switch back decorations. It works. Thanks all,
> it was great
> exercise to learn a bit of emacs internals and to make a simple hack.
>
> 2017-01-11 8:08 GMT+01:00 Arthur Miller <arthur.miller.no1@gmail.com>:
>
>> "We call it "Losedows" or "Lose OS", because if you use it, you lose
>> your freedom.
>>
>> We're glad if Emacs gives you a taste of freedom, but a taste is
>> all it can give you.  To escape from Microsoft's power, you need to
>> stop using Losedows."
>>
>> Haha :-) Indeed.
>>
>> I do run Arch Linux otherwise, but I do some consulting with programming
>> databases and GUIs in access & spss and I also play some games
>> occasionally, so I still need losedows. I know I could run it in wine and
>> pass through vga, but I feel a bit too old for that :).
>>
>> This was a great excursion in Emacs src code. I added above mention
>> method to my w32fns.c, added FRAME_DECORATED() macro to frame.h
>> a boolean_bf undecorated :1, to frame struct, initiated it to false in
>> "make_frame"
>> added an entry to frame_parms: {"undecorated",        SYMBOL_INDEX
>> (Qundecorated)},
>> added connecction to w32_frame_parm_handlers[] to x_set_undecorated at
>> same
>> place where symbol is declared in frame_parms (last in the list), added an
>> INLINE void fset_undecorated( ... ) to frame.h (not sure if it is
>> needed), and now
>> I can change my new param with lisp from emacs, but my connection seem
>> never to be called.
>>
>> By the way, I think world is better without borders, so I have modified
>> Martin's
>> x_set_undecorated to
>>
>> void
>> x_set_undecorated (struct frame *f, Lisp_Object new_value, Lisp_Object
>> old_value)
>> {
>>   HWND hwnd = FRAME_W32_WINDOW (f);
>>   DWORD dwStyle = GetWindowLong (hwnd, GWL_STYLE);
>>   /*Lisp_Object border_width = Fcdr (Fassq (Qborder_width,
>> f->param_alist));*/
>>   /*Lisp_Object undecorated = Fcdr (Fassq (Qundecorated,
>> f->param_alist));*/
>>
>>   block_input ();
>>   if (!NILP (new_value) && !FRAME_UNDECORATED (f))
>>     {
>>       dwStyle = (dwStyle & ~WS_THICKFRAME & ~WS_CAPTION);
>>       SetWindowLong (hwnd, GWL_STYLE, dwStyle);
>>       SetWindowPos (hwnd, HWND_TOP, 0, 0, 0, 0,
>>                     SWP_NOSIZE | SWP_NOMOVE | SWP_NOZORDER |
>> SWP_NOACTIVATE
>>                     | SWP_FRAMECHANGED);
>>       FRAME_UNDECORATED (f) = true;
>>     }
>>   else if (NILP (new_value) && FRAME_UNDECORATED (f))
>>     {
>>       SetWindowLong (hwnd, GWL_STYLE, dwStyle | WS_THICKFRAME | WS_CAPTION
>>                      | WS_MAXIMIZEBOX | WS_MINIMIZEBOX | WS_SYSMENU);
>>       SetWindowPos (hwnd, HWND_TOP, 0, 0, 0, 0,
>>                     SWP_NOSIZE | SWP_NOMOVE | SWP_NOZORDER |
>> SWP_NOACTIVATE
>>                     | SWP_FRAMECHANGED);
>>       FRAME_UNDECORATED (f) = false;
>>     }
>>   unblock_input ();
>> }
>>
>> So it should just switch on "undecorated" param and ignore borders (at
>> least I hope). I am not sure where do
>> I have to make change more to get it to work.
>>
>> 2017-01-10 21:39 GMT+01:00 Clément Pit--Claudel <clement.pit@gmail.com>:
>>
>>> On 2017-01-10 13:27, Eli Zaretskii wrote:
>>> > Then I suggest to add this to Emacs.  That some wm's ignore it is not
>>> > a reason to avoid having the feature for those that don't ignore it.
>>>
>>> Indeed, it would be wonderful!
>>>
>>>
>>
>