Cygwin fails to utilize Unicode replacement character

[Thomas Wolff]

Am 03.09.2018 um 19:56 schrieb Thomas Wolff:
> Am 03.09.2018 um 19:16 schrieb Corinna Vinschen:
>> On Sep  3 18:34, Thomas Wolff wrote:
>>> Am 03.09.2018 um 16:59 schrieb Corinna Vinschen:
>>>> On Sep  3 14:46, Corinna Vinschen wrote:
>>>>> On Sep  2 05:51, Steven Penny wrote:
>>>>>> On Sun, 2 Sep 2018 10:07:10, Thomas Wolff wrote:
>>>>>>> Actually, the width problem I suggested in my other response 
>>>>>>> (and even
>>>>>>> referring to the wrong character) does not apply as mintty enforces
>>>>>>> proper width in that case.
>>>>>>> Also, even with fonts that do not provide the glyph, you will 
>>>>>>> usually
>>>>>>> still see it by the Windows font fallback mechanism.
>>>>>>> Shall I make it configurable?
>>>>>> your call - here are the possible resolutions - in order of my 
>>>>>> preference:
>>>>>>
>>>>>> 1. Change the default to U+FFFD with no option
>>>>>> 2. Change the default to U+FFFD with option to change
>>>>>> 3. Leave default as is with option to change
>>>>> Ideally we could check if the current font supports a visual
>>>>> representation of 0xfffd and if not, fall back to 0x2592.
>>>>>
>>>>> Not sure how feasible that is, but it doesn't seem to be overly
>>>>> complicated.  I'm just looking into a solution for the Cygwin
>>>>> console.
>>>> Only, I can't get this working.  In theory the GDI function
>>>> GetGlyphIndicesW is supposed to allow checking if a certain character
>>>> exists.  But I'm getting a weird result.  This code:
>>>>
>>>> Â Â Â  static const wchar_t replacement_char[2] =
>>>> Â Â Â Â Â  {
>>>> Â Â Â Â Â Â Â  0xfffd, /* REPLACEMENT CHARACTER */
>>>> Â Â Â Â Â Â Â  0x2592Â  /* MEDIUM SHADE */
>>>> Â Â Â Â Â  };
>>>> Â Â Â  HWND cwnd = GetConsoleWindow ();
>>>> Â Â Â  HDC cdc = GetDC (cwnd);
>>>> Â Â Â  int rp_idx = 0;
>>>> Â Â Â  WORD gi = 0;
>>>> Â Â Â  DWORD ret = GetGlyphIndicesW (cdc, replacement_char, 1, &gi,
>>>> GGI_MARK_NONEXISTING_GLYPHS);
>>>> Â Â Â  if (ret != GDI_ERROR && gi == 0xffff)
>>>> Â Â Â Â Â  rp_idx = 1;
>>>>
>>>> always sets rp_idx to 1 when called from inside the Cygwin DLL,
>>>> independently of the actual console font.  And, here's the really 
>>>> weird
>>>> thing, it always sets rp_idx to 0 when called directly from an
>>>> application, likewise independently of the actual console font.
>>>>
>>>> Does anybody have an idea what I'm doing wrong?
>>> This works in mintty, just uploaded a patch. Maybe somehow the 
>>> GetConsole
>>> "dc" does not support this usage?
>> ¯\_(ツ)_/¯
> Dito; hold on, sorry, your code does *not* work inside mintty.
> Mine looks a bit different and I thought to have manually verified 
> it's functionally equivalent, but indeed there must be something fishy...
You still need to
 Â  SelectObject(cdc, f);
where f is the HFONT of the font you want to check.
To compare, you may check out function win_check_glyphs in file 
wintext.c in mintty.
Thomas

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