Contributing to the Inter UI font project
First off, thank you for considering contributing to Inter UI. It's people like you that make the Internet such a great place.
Following these guidelines helps to communicate that you respect the time of the people managing and developing this open source project. In return, they should reciprocate that respect in addressing your issue or suggestion.
By contributing work to the Inter UI font project you agree to have all work contributed becoming the intellectual property of the Inter UI font project as described by SIL Open Font License, Version 1.1
Types of contributions this project is looking for
More glyphs! Several glyphs, especially non-latin ones, are placeholders that need to be replaced with ones designed in the style of Inter UI. Cyrillic glyphs are especially requested.
Kerning, kerning, kerning — there are so many pairs and pairs-in-words that need to be kerned, or have their kerning improved. When adding kerning, use groups rather than individual pairs. See Kerning for more information.
Thin "master" style for lighter weights. This is a very large project and should probably be done in a branch over a longer period of time, rather than as one huge contribution/pull request.
Master fonts and interpolated derivatives
This project uses "master styles" (or "key styles") which are combined using some clever math to generate other styles that are "mixed" from two masters. Because of this, there are some very important rules you must stick to:
- When adding or removing a glyph, you must add or remove the same glyph in all master fonts. If you're using Glyphs.app, this is automatically taken care of, but not with RoboFont or some other font tools.
- When editing glyphs we must make sure:
- all masters have the same amount of paths, nodes and handles, as well as components.
- all components, paths, nodes and handles are in the same order across all masters.
- all masters have the same set of anchors.
If these rules are not followed, generated styles will fail to build.
Multiple Masters: Keeping Your Outlines Compatible is a great article on this topic.
Compiling font files
There are two ways by which you can generate font files (OTF, TTF, WOFF2, etc) from the sources files:
- Using the "export" feature in font editors like Glyphs or RoboFont
- Using Inter UI's own build system (which requires no external tools.)
Exporting from font editors is a great alternative if you just want to test things out, but using Inter UI's own build system is the way to go for "production quality" font files. The rest of this section covers how to use Inter UI's own build system, aka the toolchain.
Using the toolchain
Currently the toolchain has only been tested on macOS, and all you need is Python, which comes pre-installed with macOS, so no need to install anything. Python can easily be installed in Windows, Linux and other OSes.
You'll want to open a Terminal for this.
The first step is to initialize the toolchain itself:
This will fetch, setup and configure everything needed to build and test Inter UI.
init.sheverytime you pull new changes to the source code or before pushing source code to a remote repository.
init.shmay update the UFO source files and makefile, changes which may be required to be included in a source code change.
We can now run
make to build all font files:
$ make -j
This may take a long time (a few minutes) the first time as it generates "font instances" (i.e. all styles that are derived through interpolation from the master styles) in addition to compiling the actual font files (OTF, TTF, etc.)
The toolchain comes with a few other useful actions, one of them is
test which runs some checks on the compiled font files to make sure they behave as intended:
$ make -j test
Try & sample as you go
When making changes to the typeface and its source files, it's a good idea to sample your changes not only in a font editor or graphics editor, but also in real-world scenarios.
There are two things in particular that will help you with this:
make -j STYLE_FORMATto quickly compile only a particular style
- Interactive "Lab"
You can invoke
make with either names of styles, names of styles and file formats, or even specific filenames. Here are a few examples:
make -j Regular BoldItalic # Regular and Bold Italic make -j all_ttf # All styles but only TTF files make -j MediumItalic_web # Medium Italic as TTF, WOFF and WOFF2 make -j build/hinted/Bold.ttf # Bold TTF with autohints
All resulting font files are written to the
build directory with
InterUI- as the filename prefix. The
Makefile file contains information about more possibilities of
The interactive Lab is a great tool for quickly exploring your font files. It's a web-based tool which you start in a terminal by running:
Open up the URL printed on the screen and you can now explore your font files. Simply
make -j STYLE_web (or
make -j all_web for all styles) and reload the web page to try a new build.
See Interactive Lab for more details.
Editing source files
This font is stored and authored primarily in a unified Glyphs
.glyphs file. However, if you prefer to use a different font editor, the master styles are also maintained as UFO (Unified Font Object) files and can be edited by lots of font software, like the free and open-source FontForge or commercial apps like RoboFont.
—Important— The UFO source files are generated from the Glyphs source file. Editing the Glyphs file will cause the UFO files to be over-written. You have to commit to editing either the .glyphs file or the .ufo files.
To make life easier for you, configure your editor as follows:
- Set the grid to 128 units. This means that each grid square equals one pixel at 2x scale.
- Set "Snap points to" to a reasonably high number that's a power-of-two, like 8.
- Set "SHIFT increment" to 16
- Set "CMD SHIFT increment" to 128
Note: If you're using Glyphs, this will already be the case as this information is stored in the .glyphs file.
This project comes with a simple web-based application for debugging and previewing the font. It's a very useful tool to have when working on the font.
- Comes with a large body of sample text data (which is also editable.)
- Provides samples of the most common latin-script pairs, useful for kerning.
- Provides samples of words ordered by commonality in latin scripts with a preference for English (accessible via common-pair samples.)
- Can show the complete repertoire of the fonts, with correct glyph order and even RoboFont color labels ("marks").
- Controls for basic font properties like family, weight, italic, size, line-height, letter-spacing, etc.
- Controls for a lot of font features like ligature sets, contextual alternates, alternate numerics, etc.
- Controls for web-browser text features like
- Ability to compare Inter UI side-by-side with other fonts.
To start the lab, simply run this in a terminal (and keep the terminal running.)
You can now visit the URL printed on the screen to use the lab. Simply
make -j STYLE_web (or
make -j all_web for all styles) and reload the web page to try a new build.
An online version of the lab is available at https://rsms.me/inter/lab/ with the most recent official release of the Inter UI font files.
Kerning is the concept of harmony in the pace of characters, defined as a set of distances between specific character pairs, like "A" & "c". Good kerning makes words more readable. Oftentimes this means that when adjusting kerning, you have to look at whole words and sentences when adjusting the kerning of a pair, since the spacing between two characters should work in harmony with the spacing of all other characters.
All major font editors provide user interfaces for previewing and adjusting kerning. There is even dedicated software specifically for working with kerning.
When adding kerning, use kerning groups rather than specific pairs.
- If you're using Glyphs, read more about kerning and how the "padlock" icon affects kerning specific pairs vs groups here: https://glyphsapp.com/tutorials/kerning
- If you're editing the UFO files, the groups can be found in the
If a glyphname is missing in kerning groups, define a new group for it. Group name should reflect the most prominent or common glyph that belongs to the group. For example, "V" for a group containing "Y", "Ÿ", "V" and "W". A kerning group is specific to one "side" of a glyph (left or right) and therefore the name should reflect a glyph which side is the most relevant one. For instance, consider the character "D" which on the left side looks like "M" and "L" but on the right side looks like "O" and "C". It belongs to the "O left" group and the "M right" group. Similarly for "g" ("o left", "m right"), "p" ("m left", "o right") and many other glyphs.
Kerning groups is a really simple but incredibly time-saving way of kerning a font.
Tip: Include sample images of kerning adjustments with code pull requests that affect kerning.
misc/tools/kernsample.py is helpful in generating samples for all existing right-hand side characters given a left-hand side glyphname.
$ misc/kernsample.py src/Inter-UI-Black.ufo P -suffix MOR PAMOR P/AE MOR PJMOR PXMOR PYMOR PZMOR P/ae mor P/ampersand mor P/backslash mor P/dzcaron mor P/eightsub mor P/ellipsis mor Pfmor P/four mor P/guilsinglleft mor P/idieresisacute mor P/periodcentered mor P/quotedblbase mor Psmor P/seven mor P/slash mor Ptmor P/two mor P/underscore mor Pymor
misc/tools/kernsample.py -h for help on how to use the program.
This only includes existing kerning and is thus only useful for adjustments. Additions must still be done manually.
There are several tools included with Inter UI to help "wrangle" metrics, generate glyphs, create PDFs and so on. You can find these tools in the
misc/tools directory. They are all command-line tools and their usage can be queried by providing the help flag
For example, the fontinfo tool can be used to generate a JSON description of all metadata and merics of a TTF or OTF file:
Do I need Glyphs or RoboFont to build font files?
No, you don't. To build font files, all you need is Python. To edit the font files, you need something that can edit .glyphs or UFO files.
I'm getting errors when running
makein my terminal
This probably means that you need to run