License

Qt is now released under the Lesser General Public License meaning it can be freely linked into commercial applications.

New

Read What’s New or a more detailed description to see what’s changed since Qt 4.4 (released in May, 2008).

  • If you haven’t upgraded to Qt4, here’s what changed since Qt 3.3.4 in June, 2005.

  • Latest WebKit (aka the html display used by Apple’s Safari browser) including support for Netscape plug in so, for example, Flash can be embedded. Includes HTML 5 and CSS animation.

  • XSLT support (XML translation)

  • QtCreator is a Visual Studio like editor that works cross platform and incorporates debuging support and Qt Designer (a layout editor).

  • Mac OS X Cocoa support (latest Mac graphics library). Enables 64-bit support.

Performance

Read either Improved Performance or a white paper with more details and it requires registration so they can email it to you.

  • FileDialog is significantly faster (60x in one case)

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  • QGraphicsView optimized

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  • Clipping sped up.

  • Added SquirrelFish javascript engine which is much, much faster.

  • Added QtBenchLib to make application performance testing easier.

Noteworthy

A few other noteworthy changes: