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Microsoft Visual TrueType(VTT) command line compile tool and Python interface.


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Microsoft Visual TrueType(VTT) is a professional-level tool for graphically instructing TrueType and OpenType fonts. For details on the tool visit

Visual TrueType compiles binary from source formats included in the fonts that are instructed with Visual TrueType.

This repo contains the source for the compilers of Visual TrueType. The compilers can compile the high level VTT Talk source to a lower level assembler source and then can assemble that source to corresponding binaries. Since VTT can also generate variation 'cvar' data for variable fonts, the compilers can also produce 'cvar' data from a source format. File management functions are included to prepare a font for production and to strip source formats for a final 'ship' font binary.

The source in this repo can be compiled and used in two different ways.

First is VTTCompile which is a standalone tool can VTTCompile that runs on the command line. The interface for VTTCompile is similar to VTTShell which is included in Visual TrueType download package.

Second is VTTCompilePy which is Cython based Python extension that exports interfaces enabling a Python program to compile and assemble TrueType data. This extension also provides a command line interface to the Python interface. VTTCompilePy is available on PyPi, please visit

The source code in the repo is mostly a subset of the source code of Visual TrueType as needed to produce VTTCompile. However not all of the source code included in the repo is necessary to produce VTTCompile but we optimized for including as complete source files as possible to make future maintenance easier.

For documentation of the Visual TrueType source formats visit


In the "vttcompile" folder, there is a Visual Studio Solution for Microsoft Visual Studio users, and an Xcode Project For Apple Xcode users.

For unix users (including Linux and Apple command-line), cd src && make should work. You can also cross-compile for 32-bit windows with cd src && make CXX=i686-w64-mingw32-c++, for 64-bit windows with cd src && make CXX=x86_64-w64-mingw32-c++; and use clang, enabling all the recommended warnings with cd src && make CXX=clang++ CXXFLAGS=-Wall. Build as 32-bit on 64-bit systems with cd src && make CXXFLAGS=-m32. You may need to do cd src && make CXXFLAGS="-std=c++14" to explicitly request support for the 2014 ISO C++ standard.

In the "vttcompilepy" folder is the Cython source for the Python extension but the build is done through the file in the main folder.

Setup a Python environment including dependencies in requirements-dev.txt.

To build the extension on local machine use "Python build". To install the built extension into current Python environment use "Python install". To create a distribution package for current system use "Python bdist_wheel".

The workflow Python Extension uses ciBuildWheel to build the extension across multiple platforms and optionally upload result to PyPi.

The minimum compiler requirement is support for the 2014 ISO C++ standard plus amendments.


This project welcomes contributions and suggestions. Most contributions require you to agree to a Contributor License Agreement (CLA) declaring that you have the right to, and actually do, grant us the rights to use your contribution. For details, visit

When you submit a pull request, a CLA bot will automatically determine whether you need to provide a CLA and decorate the PR appropriately (e.g., status check, comment). Simply follow the instructions provided by the bot. You will only need to do this once across all repos using our CLA.

This project has adopted the Microsoft Open Source Code of Conduct. For more information see the Code of Conduct FAQ or contact with any additional questions or comments.


This project may contain trademarks or logos for projects, products, or services. Authorized use of Microsoft trademarks or logos is subject to and must follow Microsoft's Trademark & Brand Guidelines. Use of Microsoft trademarks or logos in modified versions of this project must not cause confusion or imply Microsoft sponsorship. Any use of third-party trademarks or logos are subject to those third-party's policies.


Microsoft Visual TrueType(VTT) command line compile tool and Python interface.



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