Re: [matplotlib-devel] [PATCH] don't print undefined glyphs in ps backend

[Nicolas G. <nic...@ga...>]

> I don't remember why we did it this way originally, or if was you or I
> who did it, but if it is correct that the mapping is sometimes many
> codes point to one one glyph index, but there each glyph index must
> point to a single character code (the latter must be correct, right?)
> then reversing it seems to be the right course.  But it's been a long
> time since I delved into freetype internals ...

FreeType 2 documentation states very clearly that character codes are
mapped to glyph indices, not the opposite.

I think the mapping from glyph indices to character codes is useless,
and I've not seen any use case of that in matplotlib.

The page http://www.freetype.org/freetype2/docs/tutorial/step1.html says:

- "A face object contains one or more tables, called charmaps, that
are used to convert character codes to glyph indices."

- "To convert a Unicode character code to a font glyph index, we use
FT_Get_Char_Index, as in "glyph_index = FT_Get_Char_Index( face,
charcode );". This will look the glyph index corresponding to the
given charcode in the charmap that is currently selected for the
face."

The page http://www.freetype.org/freetype2/docs/reference/ft2-base_interface.html
says:

- "FT_Get_First_Char: This function is used to return the first
character code in the current charmap of a given face. It also returns
the corresponding glyph index."

- "FT_Get_Next_Char: This function is used to return the next
character code in the current charmap of a given face following the
value 'char_code', as well as the corresponding glyph index."

Thanks,

-- Nicolas