<html> <head> <style></style></head> <body class='hmmessage'><div dir='ltr'> <div>> Date: Mon, 11 May 2015 21:35:49 +0200 > From: khaledhosny@eglug.org > To: lsemprini@hotmail.com > CC: harfbuzz@lists.freedesktop.org > Subject: Re: [HarfBuzz] how to detect missing glyphs e.g. for font substitition > > On Mon, May 11, 2015 at 07:56:19AM +0000, Louis Semprini wrote: > > Or, must Harfbuzz callers first do a complete, separate pass where > > they run all code points of the input through some kind of mapping > > routine that uses the fonts' 'cmap' and other tables? The latter > > would be a shame because it would require the Harfbuzz caller to > > duplicate a vast amount of the complexity that is nicely hidden in > > Harfbuzz in their own code. It's also a shame because in most cases, > > no font substitution would be needed and so it would be inefficient in > > the average case. > > Some HarfBuzz users do that i.e. check the font’s cmap table to see what > characters it supports and selects fallback fonts for what it doesn’t > before even calling HarfBuzz. Others rely on HarfBuzz, for example in > LibreOffice the run is first shaped with the user selected font, then > any contiguous runs of missing glyphs are reshaped with fallback fonts, > this have also the advantage of letting HarfBuzz do its normalisation > which can result in the font supporting more characters than it declares > in its cmap table. That's good to know, but for the second group of users, how do they detect the missing glyphs? By looking for glyph index 0? Thanks. </div> </div></body> </html>