Re: [ft-devel] losing outline flags while auto-hinting

[Werner LEMBERG]

Alexei,

thanks for this small demo program!

Your problem exposes various issues.

> $ ./outflags LiberationSerif-Regular.ttf 0x2
> Liberation Serif Regular loaded...
> Loading Flags: 0x2
> Outline Flags: 0x100

> $ ./outflags LiberationSerif-Regular.ttf 0x20
> Liberation Serif Regular loaded...
> Loading Flags: 0x20
> Outline Flags: 0   <<<<<< LOST IT

Here, the flag 0x100 (FT_OUTLINE_HIGH_PRECISION) is set in line 2103
of ttgload.c, but only if FT_LOAD_NO_SCALE is not set.  The
autohinter, however, does set FT_LOAD_NO_SCALE since it applies its
own hinting.  Maybe the test for FT_LOAD_NO_SCALE should be removed.
If you do so, however, you are still bitten by the other problem:

> $ ./outflags /usr/share/fonts/default/Type1/n019003l.pfb 0x2
> Nimbus Sans L Regular loaded...
> Loading Flags: 0x2
> Outline Flags: 0x104
>
> $ ./outflags /usr/share/fonts/default/Type1/n019003l.pfb 0x20
> Nimbus Sans L Regular loaded...
> Loading Flags: 0x20
> Outline Flags: 0   <<<<<<< LOST IT

This is a bug.  Reason is that the autohinter doesn't preserve this
flag while copying around the outlines (in function af_loader_load_g).

There are two possibilities to fix this.  One of them is to extend
FT_GlyphLoader_Add and friends (in ftgloadr.c) to carry the `flags'
field also.  Another one is to store the `flags' field in
af_loader_load_g after a (sub)glyph has been loaded, and set it again
right before leaving the function.

Given that the outline flags value is (more or less) a property of the
whole glyph and not of its subglyphs, I tend to the second solution.


    Werner