After you have created the shapes of your glyphs you
must next figure out the spacing between glyphs. The space
between any two glyph has two components, the space after the
first glyph, and the space before the second glyph. In a left
to right world these two are called the right side bearing and
the left side bearing respectively.
The left side bearing may be changed by the simple expedient
of Edit->Select All
(in the outline view) and
then dragging the selected objects to the appropriate place.
The right side bearing may be changed by selecting the advance
width line and adjusting it appropriately.
However it is generally better not to set the metrics of a
single glyph in isolation, you should see the glyph in the
context of other glyphs and set it from that perspective. Use
the Window->Open Metrics
Window
command.
Any glyphs selected in the fontview (when you invoke the
metrics view) will be displayed in the metrics view. You may
change which glyphs are displayed by either typing new ones in
to the text field at the top of the view, or by dragging a
glyph from the fontview.
From here you may adjust any glyph's metrics by typing into the textfields below it, or you may select a glyph (by clicking on its image) and drag it around (to adjust the left side bearing), or drag its width line (to adjust its right side bearing).
If you want to generate a "typewriter" style font (where all
glyphs have the same width) execute an Edit->Select
All
from the fontview and then Metrics->Set
Width
. This will set the widths of all glyphs to the
same value. After doing that you might also want to execute
Metrics->Center in Width
to even out the left
and right spacing on each glyph.
If all this manual operation seems too
complicated, try
Metrics->Auto Width
.
This will automagically assign widths to glyphs. These widths
are not up to professional standards, but they are generally
reasonable approximations.
FontForge provides some support for the vertical metrics
needed for CJK fonts. First you must tell FontForge that this
font should contain vertical metrics, do this with
Element->Font Info->General->Has Vertical
Metrics
. Then in each outline glyph enable VMetrics in
the Layers palette.
You should now see a vertical advance line somewhere underneath your glyph. You may drag this line just as you would the horizontal advance (width) line.
You might imagine that there would be an easy way to set this seemingly important quantity. Unfortunately there is not.
Typographically ept applications will allow users to adjust baseline to baseline spacing, so the default value may not be all that relevant.
If you are careful in setting the left and right side-bearings you can design your font so that the spacing looks nice in almost all cases. But there are always some cases which confound simple solutions.
Consider "To" or "Av" here the standard choices are inappropriate. The "o" will look better if it can slide more to the left and snuggle under the top bar of the "T". This is called kerning, and it is used to control inter-glyph spacing on a pair-by-pair basis.
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In the above example the left image shows the
unkerned text, the right shows the kerned text. To create a
kerned pair in the metrics window, simply click on the right
glyph of the pair, the line (normally the horizontal advance)
between the two should go green (and becomes the kerned
advance). Drag this line around until the spacing looks
nice.
Sadly that statement is a simplification... Before you can
create a kerning pair you must create a kerning lookup (see
the section on
lookups). Once again you bring up the Element->Font
Info->Lookups pane and this time you must select the GPOS
(Glyph Positioning) tab at the top of the pane. Once again you
press [Add Lookup]
. This time the lookup type is
"Pairwise Positioning", and the feature is "kern" (or perhaps
"vkrn" if you want to do vertical kerning).
Once you have created your lookup you again select it and press the [Add Subtable] button (which asks you to name the subtable). Then FontForge will ask you whether you want a subtable of kerning pairs or kerning classes.
If you have many glyphs which have similar kerning features
you might wish to create a set of kerning classes (which might
say that A, À, Á, Â, Â, Ã and Ä all kern alike). However for
this example you want a kerning pair subtable.
Then FontForge will popup a dialog allowing you to set
the kerning subtable directly. You may set your kerning pairs
from here, though I prefer the metrics view myself because you
can see more glyphs and so get a better feel for the "color" of
the font.
(Some glyph combinations are better treated by creating a ligature than by kerning the letters)
FontForge has equivalent support for vertical kerning. It can read and write vertical kerning information from and to truetype, opentype and svg fonts. It allows you to create vertical kerning classes. The metrics window has a vertical mode in which you can set vertical kerning pairs. Finally it has a command which will copy horizontal kerning information to the vertically rotated glyphs (That is, if the combination "A" "V" is horizontally kerned by -200, then "A.vert" "V.vert" should be vertically kerned by -200.
(Vertical kerning is only available if the font has vertical metrics)