The document discusses the history and architecture of Qt, an open source framework for building applications and user interfaces. It summarizes that Qt was originally developed in 1991, was acquired by Nokia in 2008, and allows writing portable source code that can be compiled for multiple platforms. The core of Qt is based on the QObject class which provides features like signals and slots, memory management, and properties.

1. Cross Platform Qt Johan Thelin

2. Quick Bio Consultant – Qt/Linux Development

3. Articles, whitepapers, etc

4. Training www.stf.se Member of

5. Co-organizes FSCONS embedded November 5-7

6. The History of Qt

7. What is Qt A framework written in C++

8. For creating portable application source code – one source, multiple platforms

9. Produces native applications

10. The History of Qt Developed since 1991 by Eirik Chambe-Eng and Haavard Nord

11. Trolltech founded in 1994

12. Acquired by Nokia 2008

13. Nokia Qt Development Frameworks

14. The History of Qt Originally Qt/X11 and Qt/Windows X11 used Free Qt License, later QPL

15. Windows was closed source Qt/OS X was released in 2001 (Qt 3.0) OS X was closed source 2005 all platforms released under GPL

16. 2009 all platforms released under LGPL

17. The History of Qt The overall goal has been portable source code and the best framework Code Less

18. Create More

19. Deploy Everywhere

20. The Architecture of Qt

21. The Modules of Qt QtGui QtSql QtNetwork QtWebKit QtSvg QtOpenGL QtOpenVG QtMultimedia QtScript QtXml QtXmlPatterns Phonon QtDBus QtTest

22. The Modules of Qt Modules are libraries in themselves

23. Can be activated or disabled at compile time

24. Allows tweaking of feature set and footprint

25. As easy as CONFIG += sql network

26. All modules share the Qt API design

27. All modules fit together

28. Key Concepts The QObject class makes Qt convenient Simplified memory management

29. Signals and slots

30. Introspection

31. Properties

32. QObject – Memory Mgmt Each QObject can have a parent

33. Parents delete all children upon destruction MyDialog::MyDialog(QWidget * parent ) : QDialog( parent ) { QPushButton *okButton = new QPushButton( this ); QPushButton *cancelButton = new QPushButton( this ); ... } MyWindow::useDialog() { MyDialog dlg(this); if(dlg.exec() == QDialog::Accepted) ... }

34. QObject – Signals and Slots Dynamic calling of functions One interface for all “callbacks”

35. Works seamless across thread boundaries

36. Creates re-usable components class QPushButton : ... { ... signals : void clicked(); ... }; class QListWidget : ... { ... public slots : void clear(); ... }; connect (button, SIGNAL(clicked()), list, SLOT(clear()));

37. QObject – Signals and Slots Inside the button class

38. Signals and function pointer tables, etc are generated by the meta object compiler, moc

39. Invoked at compile time and generates additional vanilla C++ source code emit clicked();

40. QObject - Introspection moc extracts more information, e.g. class names and inheritance

41. This enables introspection Dynamic object creation, casting, method calling, etc

42. Great when creating language bindings

43. Makes RTTI work across library boundaries

44. QObject - Properties QObject and moc also add support for properties, e.g.

45. Great when binding to dynamic languages

46. Great when serializing objects

47. Can be used to add extra information to existing classes. Useful in combination with visitor classes class QLabel : ... { Q_PROPERTY (QString text READ text WRITE setText ...) ... }

48. More Qt The power of C++ combined with the flexibility and ease of dynamic languages

49. Qt is more Great documentation

50. Large community

51. High quality code

52. etc

53. Qt Today

54. Examples of Qt in Use KDE

55. Google Earth

56. Nokia N900

57. Available Qt Platforms Official Ports X11

58. Windows

59. Mac OS X

60. Embedded Linux

61. Windows CE

62. Symbian

63. Maemo / MeeGo Other Ports OpenSolaris

64. Haiku

65. OS/2

66. iPhone

67. Android

68. webOS

69. Kindle DX

70. QNX

71. wxWorks

72. Available Qt Bindings C++

73. C# (.net)

74. Ada

75. Java

76. JavaScript

77. Lisp

78. Lua

79. Perl

80. PHP

81. Python

82. Ruby

83. etcetera Qt is developed in C++

84. The QtScript module enables JavaScript integration

85. PyQt is very popular

86. The smoke bindings generator from KDE makes it easy to create more bindings

87. Qt Today The core value and main objective still holds true: portable source code

88. The goal of Qt is to blend in everywhere

89. Portability Tips and Tricks

90. Portability - Interfaces QStyle QCommonStyle QMotifStyle QWindowStyle QS60Style QProxyStyle QCDEStyle QMacStyle QPlastiqueStyle QWindowsXPStyle QCleanlooksStyle QGtkStyle QWindowsVistaStyle

91. Portability - Interfaces Not all custom widgets are style aware! void MyWidget::paintEvent(QPaintEvent *event) { QPainter painter(this); QStyleOptionFocusRect option; option.initFrom(this); style()->drawPrimitive (QStyle::PE_FrameFocusRect, &option, &painter, this); }

92. Portability - Backends ... QPainter QPaintEngine QRasterPaintEngine X11 Windows OpenGL SVG

93. Portability - Backends The QPainter acquires a raster engine through the QPaintDevice interface implemented by all QWidget classes void MyWidget::paintEvent(QPaintEvent *event) { QPainter painter(this) ; QStyleOptionFocusRect option; option.initFrom(this); style()->drawPrimitive(QStyle::PE_FrameFocusRect, &option, &painter, this); }

94. Backends For embedded Linux, there are a number of useful backends QKbdDriverPlugin

95. QMouseDriverPlugin

96. QScreenDriverPlugin For general use, there are even more Accessibility, fonts, icons, image loading and saving, styles, codecs, etc

97. Portability - Hints Qt uses flags for platform specific features. The flags are ignored when they are not valid Qt::Drawer

98. Qt::Sheet On X11, the window manager can be a factor as it handles the window decorations, e.g. Qt::WindowMinimizeButtonHint

99. Qt::WindowSystemMenuHint Mac OS X specific dialogs, gives you an ordinary dialog or window on other platforms.

100. Portability - Hints When hinting or using platform specifics – be aware of the limitations

101. Documentation: “ Indicates that the window is a Macintosh sheet. Since using a sheet implies window modality, the recommended way is to use QWidget::setWindowModality()... ” MyDialog::MyDialog(QWidget *parent) : QWidget(parent, Qt::Sheet ) { setWindowModality(Qt::WindowModal); ...

102. More Portability Defines make it possible to write dedicated code for each platform Q_OS_LINUX , Q_LITTLE_ENDIAN , etc It is possible to hook into platform specific events

103. It is possible to tweak the Qt build system to link against different libraries on different platforms

104. It is possible to enable or disable individual classes to streamline Qt

105. ... bool QWidget::x11Event (XEvent *event)

106. Portability In 99% of the cases no platform specific code is needed

107. As long as you stick to Qt APIs you do not have to worry about platforms – it just works

108. Thank you for your attention! [email_address]