Phil's notes from the Qt Developer Days conference (11-29-2011 to 12-01-2011), San Francisco
http://qt.nokia.com/qtdevdays2011

Qt Quick / QML

• Qt Quick for "liquid GUIs", touch devices.
• QML looks like CSS (it's declarative), and uses JavaScript for binding and specialization.
• For desktop development, use the "Qt Components for Desktop" module. Very preliminary, but already in use by developers.
  • Surprisingly little QML code was necessary to nicely implement basic widgets.
  • "Unsupported Research", but usable in Qt 4.7
• Qt Quick has a better formulation of "QAbstractItemModel" -- based on providing application data rather than display properties (e.g. alignment).
• Qt Quick with C++ development uses just a little JavaScript for the GUI glue. Supports Signal / Slot connections.
• Qt4 and Qt5 have different integration technologies for Qt Quick. Qt4 uses a QDeclarativeView, based on the Graphics View framework. Qt5 uses instead an efficient implementation of OpenGL. Mixed application development not recommended at this time, at least until Qt5 is more mature.

Qt5

• Qt widgets are completely supported (i.e. no need to port to QML / Qt Quick / OpenGL / JavaScript).
• Qt Quick WILL also be positioned for desktop development.
• Porting script: fixqt4headers, will do most of the work to port from Qt4.
• Qt Creator will work well for widget-based development
• [Question response]: QDom will move out of the Qt standard libraries, but will be available as an optional module, and is expected to be picked up by the Qt Project.
• Beta: March/April 2012
• Release: 1st half of 2012.

Qt5 will support Linux/Wayland as an alternative to Linux/X11.

• Linux/Wayland will be one of the "reference platforms" for Qt5 (including also Windows, Mac OS X, and Linux/X11).
• Also, Ubuntu (Linux) is planning on working on the "graphics stack" for Wayland

Development of Multi-threaded applications

• Before using QMutex's for fine-grained contention, look at the QAtomic API as a "lock-free" alternative.
• QConcurrent is not really recommended.
• QMutex will be cheaper in Qt5 (than it had been in Qt4) in non-contention scenarios.

Qt Versions

• 4.7: Qt Creator; Qt Quick 1.0; Significant Webkit; HTML 5
• 4.8: Peformance & Quality improvements (incl. file access); Specific widget improvements; New Webkit 2.2 (HTML 5); Qt Quick 1.1.
  • Continued Developement: into 2012
  • Standard Support:: into 2014
  • Extended Support (necessary patch releases): beyone 2014.
• 5.0: Qt Quick 2.0; Qt widgets officially supported; C++ widgets will not require OpenGL.

Qt Commercial by Digia

• Significant quality control efforts in the commercial distribution. ("Bamboo" build and test system).
• Some Digia widget development / "Qt Commercial Add-ons" in Qt5 will be available to only commercial developers.
  • charting, data visualization
  • "cloud"
  • printing & PDF.
• [In conversation: this needs to be confirmed]: There may be no going back to Qt Commercial once RiverWare has been released under LGPL.
• 4.8 priority: error correction and performance improvements (earlier availability than the open distribution); Better Visual Studio integration.

Debugging

• qDebug(), qWarning(), QFatal(), of course.
  • Breakpoint for these outputs: qt_message_output().
  • Best if QObjects are assigned an object name.
• QObject::dumpObjectInfo()
• Visual Studio Qt Integration Plugin: http://developer.qt.nokia.com/wiki/QtVSAddin
• Abstract Item Model Test: http://developer.qt.nokia.com/wiki/Model_Test
• Environment variables: Q_FUNC_INFO, QT_FATAL_WARNINGS
• ... QT_FLUSH_PAINT [_EVENT], QT_FLUSH_UPDATE
  ... highlights repainted area, useful for debugging paint performance
• QT_DEBUG_PLUGINS ("why isn't it loading my SQL driver?")
• ... Unix: LD_DEBUG
• Valgrind Suite (LOTS OF STUFF): But Linux and Mac only.
• GammaRay test suite for Qt Creator: https://github.com/KDAB/GammaRay

Misc Notes:

• Qt Creator (IDE in the Qt SDK) looks very good.