RE: [Devel] unpatented hinting system for Dynalab fonts, etc

[Graham Asher]

Here is a revised (and tested) design for the use of unpatented hinting. It
overcomes the obvious objection to my earlier system that it imposed a
run-time overhead even when full hinting was used.

1. I have realised that TrueType hinting, insofar as modifying the way the
bytecode interpreter works, cannot be treated as a parameter to glyph
loading, but must be a face property, because the bytecode interpreter is
run to set the CVT values when the font size is set. Therefore I have
decided that unpatented hinting is to be set using a parameter tag passed to
FT_Open_Face. The parameter FT_PARAM_TAG_UNPATENTED_HINTING, defined in a
new header file, \freetype\ttunpat.h, is used.

2. Unpatented hinting code is compiled only if the new configuration macro
TT_CONFIG_OPTION_COMPILE_UNPATENTED_HINTING is defined, and, of course,
TT_CONFIG_OPTION_BYTECODE_INTERPRETER must also be defined in the normal
way. This means that if TT_CONFIG_OPTION_COMPILE_UNPATENTED_HINTING is not
defined, no extra code is compiled or executed and there is no run-time
overhead. (The overhead is very small, however, even when the code is
compiled.).

3. If in addition to these two macros,
TT_CONFIG_OPTION_FORCE_UNPATENTED_HINTING is defined, the unpatented hinting
system is always used, for every face that is opened.

I shall wait for approval from David Turner before checking this in.

Graham Asher