Re: Cygwin fails to utilize Unicode replacement character

[Thomas Wolff <towo@towo.net>]

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:
>
>    static const wchar_t replacement_char[2] =
>      {
>        0xfffd, /* REPLACEMENT CHARACTER */
>        0x2592  /* MEDIUM SHADE */
>      };
>    HWND cwnd = GetConsoleWindow ();
>    HDC cdc = GetDC (cwnd);
>    int rp_idx = 0;
>    WORD gi = 0;
>    DWORD ret = GetGlyphIndicesW (cdc, replacement_char, 1, &gi,
>                                  GGI_MARK_NONEXISTING_GLYPHS);
>    if (ret != GDI_ERROR && gi == 0xffff)
>      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?

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