This gets me to the milestone where the new version isn't uniformly
worse than the old one when rendered by FreeType at 10.5 ppem (the
worst size I've found).
The big problem I still have is that letters with three horizontal
stems (like 'B') get their middle stem rounded down in this version
and up in 002.009. I think this is because FontForge generates and
edge hint and not a stem hint at the bottom of the character, which
also makes bottom stems rather fuzzy. This version gives sharper
stems, but the characters all end up looking top-heavy.
If we're imitating a CRT character generator, obviously we should
process pixels line-by-line, not column-by-column. But that means
writing "for (y ...)" before "for (x ...)" which isn't the instinctive
way I did it.
So now that's corrected and the Y loops are outside the X loops, which
should make any debugging output easier to follow. This has been
confirmed not to change FreeType rendering at 10.5 ppem.
Type 1 fonts (and by extension CFF fonts) are required to have their
outer contours go counter-clockwise. Bedstead has always generated
outlines clockwise and depended on FontForge to correct them. Now
they're generated counter-clockwise as is proper, which will be fine
until I decide I want TrueType outlines instead.
This makes no difference to FreeType's rendering at either 20 ppem or
10.5 ppem
Now there's a select_hints() function that decides what hints should
be emitted, and emit_hints() just handles putting those hints into a
charstring. I hope this will make each function reasonably simple.
Importantly, it means that select_hints() can be called twice, once
for horizontal stems and once for vertical ones.
TTX doesn't actually care what order we emit tables in: it will always
put them into the recommended order. So I've made the order something
that works correctly and that doesn't look too silly in TTX's console
output.
And explain in excruciating detail why it's safe. It's only actually
safe on systems (like POSIX ones) where time_t is an integer type, but
I think that's good enough for me.
If set, it is used to set the "created" and "modified" fields in the
OpenType 'head' table. This means that builds of Bedstead can be
reproducible.
The current code just casts the "long long" interpretation of the
environment variable into a time_t. This is potentially undefined
behaviour, because time_t might be a signed integer type smaller than
"long long". But I can't find a way to properly range-check it. Even
in POSIX, where time_t is required to be an integer type, there
doesn't seem to be a constant that specifies its range.
These are generated from the glyph bitmap by a similar
pattern-matching arrangement that generates the outline. Then, like
emit_path(), there's an emit_hints() that turns them into valid
charstrings. The handling of overlapping hints could be cleverer: at
the moment we emit the leftmost-possible set of hints, but we collect
a histogram of where hints are needed so could instead emit the most
useful. Or even try to do hint substitution.
This makes the Bedstead Web page at 90% zoom much prettier than
before, but it's not as good as the FontForge auto-hinter managed.
Edge hints and counter hints will probably help.
Stringifying it from a C token may have been more compact, but it was
also quite confusing because those really weren't C identifiers and
everywhere else XML appears in strings.
This pulls the conditional that works out how to render a glyph into
it's own function, doglyph(), that also handles indirecting through
aliases. Later maybe we'll properly use subroutines to share the
charstrings for aliased glyphs.
