A portable library of geometry classes for Java
Java Scala
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README.md

Pythagoras

Pythagoras is a collection of geometry classes that aims to provide performant, portable geometry routines for projects that cannot make use of java.awt.geom (for example for use in GWT projects or Android projects). In addition to original work, it contains code adapted from the Apache Harmony project and the Clyde library.

  • API documentation is available.

  • Pythagoras can be obtained via Maven Central: com.samskivert:pythagoras:1.4.1. Or you can download the pre-built jar file.

Design

Some restructuring of the java.awt.geom classes was undertaken to meet certain design goals.

  • The library is specialized on the primitive types rather than attempting to support all types in a single class hierarchy. pythagoras.f and pythagoras.d provide equivalent functionality using 32-bit and 64-bit floating point values throughout. pythagoras.i is specialized on int and contains none of the curved geometry classes.

  • The need for defensive copying is minimized by the existence of read-only interfaces for each geometric primitive, which allow no mutation of the entity. Thus a consumer that requires only to read the attributes of, for example, a Rectangle can accept an IRectangle to indicate to the caller that it will not (and indeed cannot) mutate the supplied entity. Similarly, a read-only interface can be returned to a private internal field without fear that the recipient will mutate it and wreak havoc. Note that the interfaces have a very small, but non-zero, performance cost versus direct use of the mutable classes. Use the interfaces anyway and then profile your application to determine whether there are places where you need to sacrifice code clarity and safety on the altar of higher performance.

  • The library supports garbage creation avoidance (for applications which are sensitive to garbage collection pauses, like video games). For example, in cases where entities return a Rectangle containing their bounds, a corresponding method exists which accepts a Rectangle into which to write the bounds. Further work is needed here, as some of the implementation internals create garbage that could be avoided.

  • The library attempts to minimize the size of its instances by avoiding the inclusion of any fields that are not essential to the function of a particular geometric entity. For example, no cached hash codes or cached computed bounds are maintained.

  • Helper methods associated with a given geometric primitive are separated into a utility class for each primitive. For example line-related primitives are in a class named Lines.

License

Pythagoras is released under the Apache License, Version 2.0 which can be found in the LICENSE file and at http://www.apache.org/licenses/LICENSE-2.0 on the web.