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<HTML>
<HEAD>
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<!-- AP: Created on: 11-Feb-2002 -->
<!-- AP: Last modified: 27-Mar-2009 -->
<TITLE>Building Accented and other Composite Characters</TITLE>
<LINK REL="icon" href="fftype16.png">
<LINK REL="stylesheet" TYPE="text/css" HREF="FontForge.css">
</HEAD>
<BODY>
<DIV id="in">
<H1 ALIGN=Center>
Building Accented and other Composite Glyphs
</H1>
<P>
You can use the <KBD>Element->Build->Build Accented Glyph</KBD> command
to build up accented glyphs. Or you can use
<KBD>Element->Build->Build Composite </KBD>and build slightly more
general composite glyphs (ligatures and so forth). The accented version will
not create ligatures and will not replace Alpha with A. The composite version
will do both these things. My assumption is that ligatures (like the "fi"
ligature) usually need a bit of work on the user's part to get them to look
good, in the case of "fi" the dot on the "i" needs to be fused into the hook
of the "f", and if you are careless with the command you might destroy your
work inadvertently.
<P>
What can be built?
<UL>
<LI>
Unicode specifies various normative glyph decompositions. So "Aacute" is
defined to be an "A" with an "acute" accent centered on top. Any of these
can be built (though if the glyph contains no accents it will need to be
built with the build composite command).<BR>
Sometimes Unicode's normative definition is not as informative as it might
be (many of the greek accents are "unified" with latin accents that they
don't really look like, the result is that following Unicode slavishly will
yield the wrong glyph). So in some cases FontForge will use a slightly different
set of glyphs than the normative decomposition.<BR>
This includes:
<UL>
<LI>
Latin accented characters
<LI>
Latin ligatures (ae, oe, fi, fl, etc)
<LI>
Greek accented characters
<LI>
Cyrillic accented characters
<LI>
Hebrew ligatures
<LI>
Arabic ligatures
<LI>
Fractions, digits inside parens, roman numerals, etc.
<LI>
The predefined Hangul characters (0xac00-0xdfaf)
</UL>
<LI>
Many of the Korean Jamo are actually ligatures of other Jamo (ssangkiyoeok
(0x1101) is composed of two kiyoeok (0x1100)). For some reason this information
is not normative unicode, but FontForge is aware of it anyway and will build
those glyphs if you ask it to.
<LI>
The glyphs "i" and "j" can be built by adding a dot accent to the dotlessi
and dotlessj glyphs
<LI>
The dotlessi and dotlessj glyphs can be built by removing the dot from an
"i" or "j" glyph
<LI>
If a glyph name has an extension, as "agrave.sc", then it will be built out
of the same components as "agrave", except FontForge will use the variants
of those components named with the same extension. So "agrave.sc" would be
built out of "a.sc" and "grave.sc". If the accent variant does not exist
then FontForge will also try the bare accent "grave".
<LI>
FontForge knows a few other things. It knows that Greek "Alpha" and Cyrillic
A both look like the Latin "A" and will replace either if you ask. (as well
as all the other similar glyphs in latin, greek, cyrillic, cherokee, etc.)
<LI>
Some glyphs are just extremely simple to build. There are a whole slew of
glyphs which correspond to zero-width spaces. FontForge will build any of
them. More usefully it will build any of the fixed size spaces 0x2000-0x200f,
and the fixed sized rules 0x2010-0x2015).
<LI>
You may use the Element->Char Info dialog to define a ligature yourself,
and FontForge will build it for you.
<LI>
In Adobe's CID glyph sets there are some pre-rotated versions of latin glyphs.
When CJK text is written vertically the convention is that any text in western
alphabets should be displayed rotated 90º clockwise. If you apply Build
Accented Glyph to one of these slots it will find the appropriate latin letter
and rotate it properly.<BR>
If a glyph's name is "vertcid_<cid>" where <cid> is a decimal
number, then it is assumed to be a vertically rotated version of the glyph
at <cid>. In non-cid-keyed fonts, if a glyph's name is
"vertuni<uni>" where <uni> is a four digit hex number, then it
is assumed to be a vertically rotated version of that unicode glyph.
</UL>
<P>
So for each selected glyph in the font view (or for the current glyph in
the outline view), and if all the base glyphs and accents needed by the glyph
have already been created then this command will delete anything that is
in the current layerand put a reference to the base glyph and another reference
to the accent glyph into the foreground. So if the current glyph were "À"
then a reference to "A" would be added to it, and a reference to "`" would
be centered above the "A". <BR>
If <A HREF="editmenu.html#From">Copy From</A> is set to All Fonts then any
bitmaps will have a similar process done -- that is to say, bitmap references
will be created (even in the outline glyph view).
<P>
Choosing accents can be a slightly tricky process. Unicode says that accented
letters are logically built out of the accents in the range 0x300-0x340,
but this does not work too well in postscript. A Type1 font works better
if the accented glyph is in the Adobe Standard Encoding, which means either
using accents around 0x2d0 or ascii glyphs. FontForge will first attempt
to find an accent around 0x2d0, then in ascii and finally in the 0x300-0x340
range. Even worse, Unicode unifies the greek and latin accents, so for greek
letters FontForge will look for accents around 0x1fbd (FontForge will also
require the presence of the double accents like 0x1fdd).
<P>
Some of Adobe's fonts have accents designed for use over upper case letters
(the nomal accents are designed for lower case), and accents designed for
use over cyrillic letters. So in such a font, if you attempt to build "Agrave"
FontForge will build it out of "A" and "Grave" (or "grave.cap", not the standard
"grave").
<P>
Not all accents should be centered above the base glyph, a cedilla is (usually)
centered underneath the base, while other accents need to be placed to the
left or right, or even overstruck. FontForge should know about proper placement
of most accents (or at least a rough approximation thereto).
<P>
Some Unicode glyphs contain more than one accent. Additional accents will
be treated similarly. This command can also be used to generate more general
composite glyphs .
<P>
Some accents (for example cedilla) are treated unexpectedly on certain letters
(different ways in different languages), so be careful of g-cedilla. Å
often merges the ring into the top of the A, but here it will float above
it. <FONT COLOR="Red"><STRONG>Be alert</STRONG></FONT>.
<P>
Placing an accent above a glyph is surprisingly tricky. Centered accents
(like grave, acute, etc.) should not really be placed in the exact center
of the glyph. For instance when placing an acute accent on top of an "a"
the accent should actually go above the highest part of the "a" which is
almost but not quite in the center of the glyph. And when placing an acute
on top of a "k" (a rare combination, but still used) the accent is centered
on the stem of the "k". Greek accents are even more baroque. FontForge knows
many oddities of accent placement, but it will never know all of them (some
letters have multiple forms depending on the font, or perhaps on the humidity
and phase of the moon).
<TABLE BORDER CELLPADDING="2" ALIGN=Center>
<TR>
<TD><P ALIGN=Center>
<IMG SRC="acenter.png" WIDTH="208" HEIGHT="281"><BR>
Center point of the glyph</TD>
<TD><P ALIGN=Center>
<IMG SRC="ahighest.png" WIDTH="208" HEIGHT="281"><BR>
Highest point of the glyph</TD>
</TR>
</TABLE>
<P>
And how accents are centered depends on the accents themselves. Usually FontForge
will try to center an accent so that the accent's center is over the base
glyph's "center". But that doesn't always work either. The grave and acute
accents are usually (but not always) centered only on the bottom part of
the glyph.
<TABLE BORDER CELLPADDING="2" ALIGN=Center>
<TR>
<TD><P ALIGN=Center>
<IMG SRC="aacutemid.png" WIDTH="131" HEIGHT="228"><BR>
Midpoint of accent</TD>
<TD><P ALIGN=Center>
<IMG SRC="aacutebase.png" WIDTH="132" HEIGHT="225"><BR>
Centered on base of accent</TD>
</TR>
</TABLE>
<P>
FontForge gives you a minuscule amount of control over where it puts accents.
There are two preference items you can set
(<A HREF="filemenu.html#prefs">File->Preferences</A>)
<UL>
<LI>
AccentOffsetPercent -- This allows you to control the amount of space between
the top of the letter and the bottom of the accent (or the bottom of the
letter and the top of the accent for accents that sink under their letters).
This is expressed as a percentage of the em size and defaults to 6%. (In
some cases there will be a little bit more space above the accent than that.
All the accents from all the lower case letters should be at the same height,
but the letter "o" is usually slightly higher than the letter "u". So all
the lower case accents will be placed at the appropriate height for "o",
even those over "u". A similar trick is done for upper case letters).
<LI>
AcuteCenterBottom -- This controls whether acute and grave (and double acute
and grave) accents are centered on the entire glyph, or just on the bottom.
</UL>
<P>
<FONT COLOR="Red"><STRONG><SMALL>NOTE:</SMALL></STRONG></FONT> So FontForge
is going to do something wrong. There are just too many areas where I am
ignorant or my taste doesn't match yours or the program has a bug. I strongly
recommend that you examine all your accented glyphs after building them and
be prepared to adjust things.
<P>
The algorithms take some account of the italicangle, but when working on
an italic (or oblique) font FontForge is even more likely to do something
you don't like.
<P>
If all else fails you can build your own accented glyphs with
<A HREF="editmenu.html#Reference">Edit->Copy Reference</A> and
<A HREF="editmenu.html#Paste">Edit->Paste</A>
<P>
<P ALIGN=Center>
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