Designspaces with python.md

Designspaces and python

Designspaces can do different things in different processes. Maybe you want to generate a variable font. Maybe you want to generate UFOs. Maybe you want to resample an existing designspace into something else. While fonttools.designspacelib contains the basic objects to construct, read and write designspaces, the ufoProcessor package can also generate instances.

Basics

First I have to make a DesignSpaceDocument object. This is an empty container, it has no masters, no axes, no path.

from fontTools.designspaceLib import *
ds = DesignSpaceDocument()

Now I will add an axis to the document by making an AxisDescriptor object and adding some values to its attributes.

ad = AxisDescriptor()
ad.name = "weight" # readable name
ad.tag = "wght" 	 # 4 letter tag
ad.minimum = 200
ad.maximum = 1000
ad.default = 400

Finally we add the axisDescriptor to the document:

ds.addAxis(ad)
print(ds)
path = "my.designspace"
ds.write(path)

This writes a very small designspace file:

<?xml version='1.0' encoding='UTF-8'?>
    <designspace format="4.0">
    <axes>
        <axis tag="wght" name="weight" minimum="200" maximum="1000" default="400"/>
    </axes>
</designspace>

Let's add some sources to the designspace: this needs the absolute path to the file (usually a ufo). When the document is saved the paths will be written as relative to the designspace document. A SourceDescriptor object has a lot of attributes, but path and location are the most important ones.

s1 = SourceDescriptor()
s1.path = "geometryMaster1.ufo"
s1.location = dict(weight=200)
ds.addSource(s1)

s2 = SourceDescriptor()
s2.path = "geometryMaster2.ufo"
s2.location = dict(weight=1000)
ds.addSource(s2)

Let's add some instances. Instances are specific locations in the designspace with names and sometimes paths associated with them. In a variable font you might want these to show up as styles in a menu. But you could also generate UFOs from them.

for w in [ad.minimum, .5*(ad.minimum + ad.default), ad.default, .5*(ad.maximum + ad.default), ad.maximum]:
    # you will probably know more compact
    # and easier ways to write this, go ahead!
    i = InstanceDescriptor()
    i.fileName = "InstanceFamily"
    i.styleName = "Weight_%d" % w
    i.location = dict(weight = w)
    i.filename = "instance_%s.ufo" % i.styleName
    ds.addInstance(i)

The XML now has all it needs: an axis, some sources and ome instances.

<?xml version='1.0' encoding='UTF-8'?>
<designspace format="4.0">
  <axes>
    <axis tag="wght" name="weight" minimum="200" maximum="1000" default="400"/>
  </axes>
  <sources>
    <source filename="geometryMaster1.ufo">
      <location>
        <dimension name="weight" xvalue="200"/>
      </location>
    </source>
    <source filename="geometryMaster2.ufo">
      <location>
        <dimension name="weight" xvalue="1000"/>
      </location>
    </source>
  </sources>
  <instances>
    <instance stylename="Weight_200" filename="instance_Weight_200.ufo">
      <location>
        <dimension name="weight" xvalue="200"/>
      </location>
      <kerning/>
      <info/>
    </instance>
    <instance stylename="Weight_300" filename="instance_Weight_300.ufo">
      <location>
        <dimension name="weight" xvalue="300"/>
      </location>
      <kerning/>
      <info/>
    </instance>
    <instance stylename="Weight_400" filename="instance_Weight_400.ufo">
      <location>
        <dimension name="weight" xvalue="400"/>
      </location>
      <kerning/>
      <info/>
    </instance>
    <instance stylename="Weight_700" filename="instance_Weight_700.ufo">
      <location>
        <dimension name="weight" xvalue="700"/>
      </location>
      <kerning/>
      <info/>
    </instance>
    <instance stylename="Weight_1000" filename="instance_Weight_1000.ufo">
      <location>
        <dimension name="weight" xvalue="1000"/>
      </location>
      <kerning/>
      <info/>
    </instance>
  </instances>
</designspace>

Whoop well done.