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John K. Luebs
2024-02-27 13:24:24 -06:00
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@@ -9,13 +9,12 @@ ljkiwi - Free LuaJIT FFI and Lua C API kiwi (Cassowary derived) constraint solve
Kiwi is a reasonably efficient C++ implementation of the Cassowary constraint solving algorithm. It is an implementation of the algorithm as described in the paper ["The Cassowary Linear Arithmetic Constraint Solving Algorithm"](http://www.cs.washington.edu/research/constraints/cassowary/techreports/cassowaryTR.pdf) by Greg J. Badros and Alan Borning. The Kiwi implementation is not based on the original C++ implementation, but is a ground-up reimplementation with performance 10x to 500x faster in typical use. Kiwi is a reasonably efficient C++ implementation of the Cassowary constraint solving algorithm. It is an implementation of the algorithm as described in the paper ["The Cassowary Linear Arithmetic Constraint Solving Algorithm"](http://www.cs.washington.edu/research/constraints/cassowary/techreports/cassowaryTR.pdf) by Greg J. Badros and Alan Borning. The Kiwi implementation is not based on the original C++ implementation, but is a ground-up reimplementation with performance 10x to 500x faster in typical use.
Cassowary constraint solving is a technique that is particularly well suited to user interface layout. It is the algorithm Apple uses for iOS and OS X Auto Layout. Cassowary constraint solving is a technique that is particularly well suited to user interface layout. It is the algorithm Apple uses for iOS and OS X Auto Layout.
There are a few Lua implementations or attempts. The SILE typesetting system has a pure Lua implementation of the original Cassowary code, which appears to be correct but is quite slow. There are two extant Lua ports of Kiwi, one that is based on a C rewrite of Kiwi. However testing of these was not encouraging with either segfaults or incorrect results. There are a few Lua implementations or attempts. The SILE typesetting system has a pure Lua implementation of the original Cassowary code, which appears to be correct but is quite slow. There are two extant Lua ports of Kiwi, one that is based on a C rewrite of Kiwi. However testing of these was not encouraging and they appear mostly unmaintained.
Since the C++ Kiwi library is well tested and widely used it was simpler to provide a LuaJIT FFI wrapper. There is also a Lua C API binding with support for 5.1 through 5.4. Since the C++ Kiwi library is well tested, it was simpler to provide a LuaJIT FFI wrapper. Now, there is also a Lua C API binding with support for 5.1 through 5.4, and since
in most common use cases all the heavy lifting is done in the library, there is usually
no practical perfomance difference between the two.
This package has no dependencies other than a supported C++14 compiler to compile the included Kiwi library and a small C wrapper. This package has no dependencies other than a supported C++14 compiler to compile the included Kiwi library and a small C wrapper.
The Lua API has a pure Lua expression builder. There is of course some overhead to this, however in most cases expression building is infrequent and the underlying structures can be reused.
The wrapper is quite close to the Kiwi C++/Python port with a few naming changes.
## Example ## Example
@@ -91,4 +90,4 @@ print(right_edge:value()) -- 500
In addition to the expression builder there is a convenience constraints submodule with: `pair_ratio`, `pair`, and `single` to allow efficient construction of the most common simple expression types for GUI layout. In addition to the expression builder there is a convenience constraints submodule with: `pair_ratio`, `pair`, and `single` to allow efficient construction of the most common simple expression types for GUI layout.
## Documentation ## Documentation
WIP - However the API is fully annotated and will work with lua-language-server. Documentation can also be generated with lua-language-server. The API is fully annotated and will work with lua-language-server. Documentation can also be generated with lua-language-server.