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<TITLE>Building accented glyphs</TITLE>
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<H1 ALIGN=Center>
Tutorial #4
</H1>
<UL>
<LI>
<A HREF="editexample.html#FontCreate">Font Creation</A>
<LI>
<A HREF="editexample.html#CharCreate">Creating a glyph (tracing outlines)</A>
<LI>
<A HREF="editspiro.html">Create glyph outlines using spiro points</A>
<LI>
<A HREF="importexample.html">Importing a glyph from Inkscape (or Illustrator,
or some other vector editor)</A>
<LI>
<A HREF="editexample2.html#Navigating">Navigating to other glyphs</A>
<LI>
<A HREF="editexample2.html#Creating-o">On to the next glyph (consistent
directions)</A>
<LI>
<A HREF="editexample3.html#consistent-stems">Consistent serifs and stem
widths</A>
<LI>
<A HREF="editexample4.html#accents">Building accented glyphs</A>
<LI>
<A HREF="editexample4.html#ligature">Building a ligature</A>
<LI>
<A HREF="editexample4.html#lookups">Lookups and features</A>
<LI>
<A HREF="editexample5.html#metrics">Examining metrics</A>
<LI>
<A HREF="editexample5.html#Kerning">Kerning</A>
<LI>
<A HREF="editexample6.html#Variants">Glyph variants</A>
<LI>
<A HREF="editexample6.html#Marks">Anchoring marks</A>
<LI>
<A HREF="editexample6-5.html#Conditional">Conditional features</A>
<LI>
<A HREF="editexample7.html#checking">Checking your font</A>
<LI>
<A HREF="editexample7.html#generating">Generating it</A>
<LI>
<A HREF="editexample7.html#Families">Font Families</A>
<LI>
<A HREF="editexample7.html#summary">Final Summary</A>
<LI>
<A HREF="editexample8.html">Bitmap strikes</A>
<LI>
<A HREF="scripting-tutorial.html">Scripting Tutorial</A>
<LI>
<A HREF="scriptnotes.html#Special">Notes on various scripts</A>
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<H2>
<A NAME="accents">Building</A> accented glyphs
</H2>
<P>
Latin, Greek and Cyrillic all have a large complement of accented glyphs.
FontForge provides several ways to build accented glyphs out of base glyphs.
<P>
The most obvious mechanism is simple copy and paste:
<A HREF="editmenu.html#Copy">Copy</A> the letter "A" and
<A HREF="editmenu.html#Paste">Paste</A> it to "Ã" then
<A HREF="editmenu.html#Copy">copy</A> the tilde accent and
<A HREF="editmenu.html#PasteInto">Paste it Into</A> "Ã" (note Paste
Into is subtly different from Paste. Paste clears out the glyph before pasting,
while Paste Into merges what was in the glyph with the what is in the clipboard).
Then you open up "Ã" and position the accent so that it appears properly
centered over the A.
<P>
This mechanism is not particularly efficient, if you change the shape of
the letter "A" you will need to regenerate all the accented glyphs built
from it. FontForge has the concept of a
<A HREF="overview.html#References">Reference</A> to a glyph. So you can Copy
a Reference to "A", and Paste it, the Copy a Reference to tilde and Paste
it Into, and then again adjust the position of the accent over the A.
<P>
Then if you change the shape of the A the shape of the A in "Ã" will
be updated automagically -- as will the width of "Ã".
<P>
But FontForge knows that "Ã" is built out of "A" and the tilde accent,
and it can easily create your accented glyphs itself by placing the references
in "Ã" and then positioning the accent over the "A". (The Unicode
consortium provides a database which lists the components of every accented
glyph in Unicode and FontForge uses this).
<P>
As an example, open the file: tutorial/Ambrosia.sfd, then select all the
glyphs at encodings 0xc0-0xff, and then press
<A HREF="elementmenu.html#Accented">Element->Build->Build Accented</A>
all the accented glyphs will magically appear (there are a few glyphs in
this range which are not accented, and they will remain blank).
<P>
FontForge has a heuristic for positioning accents (most accents are centered
over the highest point of the glyph), sometimes this will produce bad results
(if the one of the two stems of "u" is slightly taller than the other the
accent will be placed over it rather than being centered over the glyph),
so you should be prepared to look at your accented glyphs after creating
them. You may need to adjust one or two (or you may even want to redesign
your base glyphs slightly).
<H2>
<A NAME="ligature">Creating</A> a ligature
</H2>
<P>
Unicode contains a number of ligature glyphs (in latin we have: Æ,
OE, fi, etc. while in arabic there are hundreds). Again Unicode provides
a database listing the components of each standard ligature.
<P>
FontForge cannot create a nice ligature for you, but what it can do is put
all the components of the ligature into the glyph with
<A HREF="elementmenu.html#Accented">Element->Build->Build Composite</A>.
This makes it slightly easier (at least in latin) to design a ligature.
<TABLE BORDER CELLPADDING="2">
<CAPTION>
Steps to building a ligature
</CAPTION>
<TR>
<TD><P ALIGN=Center>
<IMG SRC="ffi-refs.png" ALT="ffi ligature as references" WIDTH="154" HEIGHT="277"></TD>
<TD><P ALIGN=Center>
<IMG SRC="ffi-unlink.png" WIDTH="154" HEIGHT="277" ALT="ffi after unlinking references"></TD>
<TD><P ALIGN=Center>
<IMG SRC="ffi-moved.png" WIDTH="154" HEIGHT="277" ALT="ffi after lowering first f"></TD>
<TD><P ALIGN=Center>
<IMG SRC="ffi-rmoverlap.png" ALT="ffi after doing remove overlap" WIDTH="154"
HEIGHT="277"></TD>
<TD><P ALIGN=Center>
<IMG SRC="ffi-caret.png" ALT="ffi after adjusting ligature carets" WIDTH="154"
HEIGHT="277"></TD>
</TR>
<TR VALIGN="Top">
<TD>Use the <A HREF="elementmenu.html#CharInfo">Element -> Glyph Info</A>
dialog to name the glyph and mark it as a ligature. Then use
<A HREF="elementmenu.html#Accented">Element -> Build -> Build
Composite</A> to insert references to the ligature components.</TD>
<TD>Use the <A HREF="editmenu.html#Unlink">Edit-> Unlink References</A>
command to turn the references into a set of contours.</TD>
<TD>Adjust the components so that they will look better together. Here the
stem of the first f has been lowered.</TD>
<TD>Use the <A HREF="elementmenu.html#Remove">Element -> Remove Overlap</A>
command to clean up the glyph.</TD>
<TD>Finally drag the ligature caret lines from the origin to more appropriate
places between the components.</TD>
</TR>
</TABLE>
<P>
Some word processors will allow the editing caret to be placed inside a ligature
(with a caret position between each component of the ligature). This means
that the user of that word processor does not need to know s/he is dealing
with a ligature and sees behavior very similar to what s/he would see if
the components were present. But if the word processor is to be able to do
this it must have some information from the font designer giving the locations
of appropriate caret positions. As soon as FontForge notices that a glyph
is a ligature it will insert in it enough caret location lines to fit between
the ligature's components. FontForge places these on the origin, if you leave
them on the origin FontForge will ignore them. But once you have built your
ligature you might want to move the pointer tool over to the origin line,
press the button and drag one of the caret lines to its correct location.
(Only Apple Advanced Typography and OpenType support this).
<P>
There are a good many ligatures needed for the indic scripts, but Unicode
does not provide an encoding for them. If you wish to build a ligature that
is not part of Unicode you may do so. First <A HREF="faq.html#new-name">add
an unencoded glyph to your font</A> (or if your font is a Unicode font, you
could use a code point in the private use area), and name the glyph. The
name is important, if you name it correctly FontForge will be able to figure
out that it is a ligature and what its components are. If you want to build
a ligature out of the glyphs "longs", "longs" and "l" then name it
"longs_longs_l", if you want to build a ligature out of Unicode 0D15, 0D4D
and 0D15 then name it "uni0D15_uni0D4D_uni0D15".
<P>
Once you have named your ligature, and inserted its components (with Build
Composite), you probably want to open the glyph,
<A HREF="editmenu.html#Unlink">Unlink your References</A> and edit them to
make a pleasing shape (as above).
<H2>
<A NAME="lookups">Lookups and Features</A>
</H2>
<P>
<IMG SRC="fontinfo-lookups.png" WIDTH="602" HEIGHT="534" ALIGN="Right">Unfortunately
simply creating a ligature glyph is not enough. You must also include information
in the font to say that the glyph is a ligature, and to say what components
it is built from.
<P>
In OpenType this is handled by lookups and features. A lookup is a collection
of tables in the font which contain transformation information. A feature
is a collection of lookups and is a provides semantic information to the
world outside the font about what that set of lookups can be expected to
do. So in the example above the lookup would contain the information that
"f" + "f" + "i" should turn into "ffi", while the feature would say that
this is a standard ligature for the latin script.
<P>
So the first time you create a ligature glyph you will need to create a lookup
(and a lookup subtable) in which the information for that glyph will reside.
Any subsequent ligatures can probably share the same lookup and subtable.
<P>
(This may seem like overkill for latin ligatures, and perhaps it is, bt the
complexity is needed for more complex writing systems).
<P>
You would open the Lookups pane of the
<A HREF="fontinfo.html#Lookups">Element->FontInfo</A> command and press
the <CODE>[Add Lookup] </CODE>button. This will give you a new dialog in
which you can fill in the attributes of your new lookup.
<P>
<IMG SRC="AddLookup-Liga.png" WIDTH="439" HEIGHT="427" ALIGN="Left">You must
first choose the lookup type. For ligatures this should be "Ligature
Substitution". You may then bind this lookup to a feature, script and language
set. The "ffi" ligature is a standard ligature in latin typesetting so it
should be bound to the 'liga' tag, and the 'latn' script. (If you click on
the little box to the right of "liga" you will get a pulldown list of the
so-called "friendly names" for the features. "liga" corresponds to "Standard
Ligatures").
<P>
The language is a bit tricky. This ligature should probably be active for
all languages except Turkish that use the latin script (Turkish uses a dotlessi
and it is not clear whether the "i" in the "fi" and "ffi" ligatures has a
dot over it). So we want to list all languages but Turkish. That's a lot
of languages. The convention instead is that if a language isn't mentioned
explicitly anywhere in the font then that language will be treated as the
"default" language. So to make this feature not be active for Turkish, we'd
have to create some other feature which specifically mentioned Turkish in
its language list.
<P>
Underneath the feature list is a set of flags. In latin ligatures none of
these flags need be set. In Arabic one might want to set both "Right to Left"
and "Ignore Combining Marks".
<P>
Next the lookup must be given a name. This name is for your use and will
never be seen in the real font. The name must be distinct from the name of
any other lookup however.
<P>
Finally you get to decide whether you want the ligatures in this lookup to
be stored in afm files.
<P>
<IMG SRC="subtable-ffi.png" WIDTH="421" HEIGHT="215" ALIGN="Right">Once you
have created a lookup, you must create a subtable in that lookup. Select
the lookup line (in the Lookups pane of Font Info) and press <CODE>[Add
Subtable]</CODE>. This is a fairly simple dialog... you simply provide a
name for the sub-table, and then another dialog will pop up and you will
(finally) be able to store your ligature information.
<P>
<FONT COLOR="Red"><STRONG><BIG>CAVEAT: </BIG></STRONG></FONT>OpenType engines
will only apply features which they believe are appropriate for the current
script (in Latin scripts, Uniscribe will apply 'liga'). Even worse, some
applications may choose not to apply any features ever (Word does not do
ligatures in latin -- though this may have changed with the 2007 release?).
<A HREF="http://www.microsoft.com/typography/specs/default.htm">Microsoft
tries to document </A>what features they apply for which scripts in Uniscribe,
but that isn't very helpful since Word and Office have quite different behavior
than the default.
<P>
<P>
<P ALIGN=Center>
-- <A HREF="editexample3.html">Prev</A> -- <A HREF="overview.html">TOC</A>
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