This is a rewrite of add_glyphs in third_party/color_emoji. The
primary motivation was to move special aliasing rules out of that
code and use an external aliases file instead. This new version
is a bit more thorough about aliasing, and hopefully a little
easier to read.
The new add_glyphs takes its parameters using keywords, so
the invocation in the Makefile changed (as well as the path to
the tool).
emoji_aliases.txt was extended to add the flag aliases that were
formerly defined in the old add_glyphs code.
add_aliases was modified so the name of the alias file could be
passed in as a parameter to the main utility function that reads
the alias mapping from the file.
The new code expects all glyphs used by the template GSUB tables
to be named in the GlyphOrder table, but doesn't require the cmap
and hmtx table to be fleshed out. The new code fleshes these out
when it processes the sequences to add. As a result the cmap and
hmtx tables in the template were truncated.
The new code also sorts the GlyphOrder table when it extends/rebuilds
it.
Since subregion flag sequences consist of BN and ON they can be
impacted by bidi, and once again we have the problem that these are
processed in visual order so we need GSUB rules such that we can
handle them in either direction. All subregion flag sequences
contain U+E007F, so we use that as a trigger for adding the
reversed sequence.
We also need to handle emitting the missing flag glyph for the
reversed sequences.
And we also want to strip out tag glyphs when the context is reversed.
This means the chaining context should include 'E007F' as well.
Instead of writing code to build the additional lookups needed for
subregion missing flag handling, this adds a GSUB table to the
template and lets add_glyphs do its normal thing to the first
GSUB lookup.
- fix ascent/descent in hhea and os/2 to match noto UI expectations,
zero linegap, clear useTypoMetrics bit, set weight to regular (400).
- add missing entries to name table, update revision
- map U+0000 to null glyph (not .notdef)
In addition, this tweaks the Makefile in some small ways:
- quiet zopflipng output somewhat (listen to your cpu fan to know
that something's happening) :-)
- make flag-symlinks target an order-only dependency (it was triggering
quantize+compress even when images hadn't changed)
- add comment about how to bypass make bug if multithread hangs
The new emoji assets (in sync with Android Lollipop) were slightly
smaller in size. Replacing with a corrected size.
Also update the font version to sync with Android again.
Doug Felt