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This is a Rust implementation of the Cassowary constraint solving algorithm (Badros et. al 2001). It is based heavily on the implementation for C++ at nucleic/kiwi. The implementation does however differ in some details.

Cassowary is designed for solving constraints to lay out user interfaces. Constraints typically take the form “this button must line up with this text box”, or “this box should try to be 3 times the size of this other box”. Its most popular incarnation by far is in Apple's Autolayout system for Mac OS X and iOS user interfaces. UI libraries using the Cassowary algorithm manage to achieve a much more natural approach to specifying UI layouts than traditional approaches like those found in HTML.

This library is a low level interface to the solving algorithm, though it tries to be as convenient as possible. As a result it does not have any intrinsic knowledge of common user interface conventions like rectangular regions or even two dimensions. These abstractions belong in a higher level crate.

For more information, please read the documentation.

Getting Started

Add the following to your Cargo.toml:

cassowary = "^0.3.0"

Please read the documentation (linked above) for how to best use this crate.


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Unless you explicitly state otherwise, any contribution intentionally submitted for inclusion in the work by you, as defined in the Apache-2.0 license, shall be dual licensed as above, without any additional terms or conditions.