bug#19994: 25.0.50; Unicode keyboard input on Windows

[Ilya Zakharevich]

On Wed, Mar 04, 2015 at 08:01:01PM +0200, Eli Zaretskii wrote:
> > +static int
> > +get_wm_chars (HWND aWnd, int *buf, int buflen, int ignore_ctrl, int ctrl, 
> > int
>                             ^^^^^^^^
> Why 'int' and not 'wchar_t'?

This is for a Unicode chars.  They won’t fit into (Windows’ style) wchar_t.

> > +  while (buflen &&                             /* Should be called only 
> > when  w32_unicode_gui */
> > +         PeekMessageW(&msg, aWnd, WM_KEYFIRST, WM_KEYLAST, PM_NOREMOVE | 
> > PM_NOYIELD) &&
> 
> Indeed, any "wide" APIs should only be called when w32_unicode_gui is
> on, and there should be alternative code for when w32_unicode_gui is
> off.  We still try to support Windows 9X.

The caller ensures this.  Yes, assert() would be beneficial here.

> > +  int ctrl_cnt, buf[1024], count, is_dead;
> 
> I think buf[] should be an array of wchar_t.  Also, will this code
> work for the non-w32_unicode_gui mode?

This code is pure-GUI.  For non-GUI “bindable” input on Windows the
major hurdle is that 

  (A) I know no way to distinguish a “prefix key” (deadkey) keypress
      from a keypress which should trigger user bindings;

  (B) with “non-destructive ToUnicode()”, one WOULD be able to
      distinguish these two cases, — but I have no clue how to find
      out the current keyboard layout of a console session.

      (There is a lot of examples of code which returns the keyboard
       layout of a window; — but these examples do not work for
       console sessions.  I suppose that the reason is that the window
       is actually owned by a system process, and one does not have
       permissions to access its properties.)

Thanks,
Ilya