Kirill Grouchnikov has announced a Release candidate for Substance 5.0 on his Pushing Pixels site. Hosted on the Java.net Projects site, Substance Java Look & Feel is a library that provides configurable and customizable look and feel for Swing applications. In its recent development, Substance "has undergone significant internal and external changes to address major performance issues and to ensure the long-term code health of the project."

The Roadmap for Substance 5 that was published this past April outlined the major changes that were in the first Substance 5 code drop. The new release candidate builds on these enhancements and improvements.

Here are the most important changes in Substance 5.0:

• Moving to Java 6 as the minimum runtime requirement.
• Addressing the performance issues. While the first announced drop was 20% faster than release 4.3, the release candidate is 3.5 times faster on static scenarios and 2.7 times faster on dynamic scenarios as measured by the LightBeam testbed.
• New client property to allow using per-window skins.
• Enhanced theming layer.
• Removed 16 VM flags and left only 2.
• Removed 15 client properties, consolidated 3 others into 2 and added 1 new.
• Removed 54 API methods on the main class, pushing some functionality into the theming layer.
• Consolidated theme pack, watermark pack and button shaper pack into the Extras pack that also provides additional skins.

See the release notes for details of what's new in Substance 5.0.

Version 5.0 includes a lot of important "under-the-hood" changes, that don't fit into the category of new or improved features. As happens with any ongoing development project, splicing in new features and enhancing existing features, while also trying to meet the community's needs in a timely manner, ultimately compromises good design principles as successive releases are put out. In developing Substance 5.0, the project team took the time to address this: the new version includes substantial refactoring of the code base, eliminating complications that had built up during the development of the past several releases, thus bringing the code back into a "clean and manageable state." The refactoring undoubtedly contributed in some measure to the enormous performance improvements in Substance 5.0 compared with Substance 4.3.

Kirill's announcement post includes images of Substance in action and a launch button that lets you run a WebStart application presenting Substance's features.

The final release of Substance 5.0 is scheduled for September 15. Support of Substance Version 4.3 (the last version that can run on Java 5) continues, but that version has now entered long-term support mode: "At the present moment this version has thirteen bug fixes backported to it from the main development trunk."

Developers are encouraged to download Substance 5.0RC, give it a ride, and support the project by reporting any problems you may note.