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.
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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.
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XSLT support (XML translation)
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QtCreator is a Visual Studio like editor that works cross platform and incorporates debuging support and Qt Designer (a layout editor).
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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.
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Added SquirrelFish javascript engine which is much, much faster.
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Added QtBenchLib to make application performance testing easier.
Noteworthy
A few other noteworthy changes:
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Networking classes have better proxy support and detection of system settings
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Writing OpenDocument formatted text
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Stylesheets now work on Mac OS X
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Better translucent windows
Pete Ware 