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Adobe Variable Font Prototype

Variable font in OpenType-CFF2 and TrueType formats, made from UFO sources derived from Source Serif Pro, designed by Frank Grießhammer.

The font files are intended to serve as test cases for environments and workflows that aim to support OpenType variable fonts.

The fonts are functional but have some limitations — see Current limitations. We plan to update them as the tools improve.

Font characteristics

Adobe Variable Font Prototype contains two axes — weight and contrast — five design masters, and eight named instances — Extra Light, Light, Regular, Semibold, Bold, Black, Black Medium Contrast, and Black High Contrast.

The weight axis has an intermediate master (master_1), and the design space can be thought of as having the shape of a square triangle. This is achieved by using master_0 twice, and by having master_4 along the diagonal defined by master_0 and master_3. This arrangement effectively collapses half of the original rectangular-shaped design space, concealing interpolation imperfections that would be visible otherwise. See design space notes for more details.

The font also contains transitional designs for the glyphs $ (dollar) and ¢ (cent), in which the inner-counter part of the stroke is removed, when the weight axis reaches Bold or heavier.

The font supports the Adobe Latin 2 character set, GPOS kerning, and the GSUB features listed below.

pnum (proportional figures)
tnum (tabular figures [default])
onum (old-style a.k.a. text figures)
lnum (lining figures [default])
zero (slashed zero)
case (case-sensitive forms such as parentheses, hyphen)
liga (ligatures fi fl ft)

Downloading the font files

Building the fonts from source

Requirements

  • Python 3.6 or later. We recommend not using your system-installed Python if you are using macOS or a Linux system with Python 3 pre-installed. Instead, use either an installer from Python.org or use Homebrew (macOS only).

  • We also recommend the use of a Python virtual environment.

  • Install the requirements with pip:

    pip3 install -r requirements-dev.txt

Build command

With the requirements installed, you can build with the supplied build script:

macOS and Linux:

sh buildFont.sh

Windows:

cmd buildFont.sh

Build process

The buildFont.sh script first builds the OpenType-CFF2 font with the FDK tools buildMasterOTFs and buildCFF2VF. The first tool generates OpenType-CFF fonts from each of the UFO masters. And the second takes the set of OTFs built in the previous step, and combines them to produce the CFF2 variable font.

The CFF2 table is then subroutinized with FDK's tx tool, and the modified table is replaced in place using FDK's sfntedit tool.

Next, fontmake is used for building the variable TrueType font.

Finally, sfntedit is used for copying/replacing several tables between the OTF and TTF fonts.

Testing

A test suite is available to check the built fonts to ensure they were built with expected values. You can initiate the tests with:

pytest tests

The tests are designed to catch unexpected regressions that might be caused by changes in tools or other environment differences.

Current limitations

  • Support for the variable OTF-CFF2 flavor is not as broad as for the variable TTF flavor.
  • Neither of the fonts is hinted.