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#1 Re-export TTF changes line spacing

Paul Evans

I'm trying to edit the Bistream Vera Sans Mono font to
add some new glyphs that are useful in XTerms, as well
as generate more of the combined accent glpyhs
automatically, but I keep coming up against a problem.

If I just open up the original .TTF file, set a new
name in the Font Info page, and re-export it out as a
.TTF file, the new font generates lines that are
somewhat taller than the original. I've compared the
ascent, descent and line gap parameters between the two
fonts, again in the Font Info page, and I can't see any
differences. Though, I have no other font editor by
which to compare them.. there may be some subtle
differences I can't see...


  • Paul Evans
    Paul Evans

    Logged In: YES

    Mmm... I should clarify that statement a bit more...

    It appears that only xterm is affected by this; in both gvim
    and OpenOffice the two fonts look identical.

    • status: open --> closed
    • status: closed --> closed-wont-fix
  • Logged In: YES

    Unfortunately this is not really a bug in fontforge, but a
    bug in the way applications implement truetype/opentype fonts.

    Line spacing should be set by the typographic ascent/descent
    parameters of the OS/2 table, but it is often set to the win
    ascent/descent parameters. According to the spec these are
    supposed to be the font's bounding box (or in some rare
    cases larger). FontForge sets these fields as spec says they
    are to be set. In erroneous applications that can cause the
    linespacing to be odd.

    If you want complete control over these fields look at
    http://mensis.sf.net/ this lets you set them however you want.