Re: [ft-devel] Taming CFF_CONFIG_OPTION_DARKENING_PARAMETER_Y* for a gamma of ~2.2/sRGB?

[Nikolaus Waxweiler]

> As soon as you switch to a new size, simply recompute the values.

Done! I'm almost there. I have extended AF_FaceGlobals to hold:

 ...
 FT_UShort stem_darkening_for_ppem;
 FT_Pos    darken_x;
 ...

and modified af_loader_load_g() to do:

 ...
 error = FT_Load_Glyph( face, glyph_index, flags );
 ...
 if ( face->size->metrics.x_ppem != 
loader->globals->stem_darkening_for_ppem )
   af_loader_compute_darkening( ... );
 if ( slot->format == FT_GLYPH_FORMAT_OUTLINE )
   FT_Outline_EmboldenXY(..., ...->darken_x, 0);
 ...

That works for size changes. I have crudely... copy-pasted and adapted 
cf2_computeDarkening() into af_loader_compute_darkening(). I feel dirty 
now but IT WORKS!!! There's just one problematic line left:

 ...
 stemWidth = cf2_intToFixed(84); /* XXX fill in somehow */
 ...

That's hopefully the last step ;) Thanks for all your pointers so far! 
That helped a lot :) I uploaded a small screenshot to show how it looks 
like with the current stand-in: http://postimg.org/image/6obxidt9d/ 
(native CFF engine, emboldening autohinter, normal autohinter, all with 
a gamma of 1.8).

> A similar argument holds for `af_latin_metrics_init_widths': Only the
> stem width measured along the vertical axis is used for light hinting.

Meaning, I'd have to modify AF_*Metrics to also compute stem widths on 
the horizontal axis and use that for stemWidth? By the way, I can't 
directly access e.g. AF_LatinMetrics->axis->standard_width from my 
af_loader_compute_darkening() as I have only an AF_StyleMetrics to go 
from.. Is there a reason why standard_width is specific to writing class 
implementations of AF_StyleMetrics? I'll see if I can find a way around 
or get a hold of the implementing class somehow... but first some sleep..

> The current subpixel hinting code should already be quite near to
> that goal.

And what keeps it from being made the default mode for the native TT fitter?

Oh, and what's that about subpixel hinting in af_loader_load_glyph()?

> Certainly not.  You can't patent the omission of something if
> everything else stays the same...

;)