Re: Odp: Re: ttfautohint — additional feature requests.

[Werner LEMBERG]

>> Microsoft Calibri has embed bitmaps, but they don't appear to be
>> used, ever, at all.  Instead, GDI uses its broken hinting.  I've
>> heard Microsoft Windows has to detect for several Japanese
>> characters in the font before using embed bitmaps.
> 
> I will ask a Microsoft guy about the details.

And here they are!  I asked

  What are the preliminaries to make Windows use embedded bitmaps of a
  font?  And what about embedded graymaps?

and I got the following response:

  This is specific behavior for our DWrite engine, not GDI or
  TrueType.  DWrite is oriented around subpixel positioned text, so
  there is a tradeoff on using embedded 1 bpp bitmaps that can be
  important for legibility at smaller sizes.  (I don't know the answer
  to embedded graymaps, but I'll see if I can get an answer to that as
  well).

  For your specific question, I talked to Nick on the DWrite team, and
  he said:

    First, there has to be an EBLC table.

    Second, we define a set of representative code points for four
    East Asian scripts as follows:

      Hiragana: U+3044, U+3046, U+3093, U+3057, U+306E, U+304B
      Hangul:   U+C774, U+B2E4, U+B294, U+C758, U+C5D0, U+D558
      CHS:      U+6C49, U+5B57, U+4E2D, U+7684, U+4E2A, U+4EEC
      CHT:      U+6F22, U+5011, U+4E09, U+4E86, U+5B78, U+7232

    The font is considered a legacy East Asian font if the following
    is true for at least one of the four scripts above:

    * The cmap table specifies glyph indices for all six of the
      representative code points, and 
    * The EBLC table has bitmaps for all six of those glyph indices.


    Werner