Re: [ft-devel] [GSoC] Extending the CF2 interpreter

[Werner LEMBERG]

> The first two are between hinting on and off for Type 1.  Notice how
> the base glyphs of accented characters shift about regardless.

Interesting.  It seems to show that the problem is not in the hinting
but at a more fundamental level.

> The third is for CFF converted to Type 1.  Notice how the line
> spacing changes in discrete steps above a certain font size.  For
> 26~29pt, it shifts downwards one step, and for 30pt it seems to
> shift a little bit more.

Ditto.

> I compared the two code paths, especially the parts to do with
> metrics, but could not find what changed between that would cause
> this.  My current guess is that some metric info is not being passed
> properly from the interpreter out to the module loading the glyph,
> but this is proving hard to debug via comparing printouts of
> numbers.

In such situations, I run

  FT2_DEBUG=any:7 ftview ... &> ftview.log    ,

adjusting its command line arguments as necessary so that the number
of key presses needed to show the desired difference stays as small as
possible.  I then compare the log files with `colordiff', using option
`-x PATTERN' repeatedly to suppress output of irrelevant lines.  You
might also adjust the value FT2_DEBUG to suppress more irrelevant
data.

If this doesn't give sufficient information I start adding tracing
messages until I see the difference – in many cases it makes even
sense to add the `resolving' tracing message upstream.


    Werner