1. Qt Widgets In-Depth
QWidget Under The Surface

2. About Me
• Marius Bugge Monsen
• Qt Developer
• Qt Widgets Team Lead

3. • Widgets and Window Systems
• Flags and Attributes
• The Future of Qt Widgets

4. by extranoise on flickr
Widgets and Window Systems

5. • Widgets and Window Systems
• Window Systems
• Windows and Widgets
• Updates and Painting
• Events and Loops

6. • Widgets and Window Systems
• Window Systems
• Windows and Widgets
• Updates and Painting
• Events and Loops

7. QWS SunView
MiniGUI Metisse
Rio Microwindows
DM Fresco/Berlin
8 1/2 GEM ManaGeR
HP Windows OOHG
Xynth
MicroXwin Intuition
Y FBUI
NeWS
NeXT DPS Quartz
Wayland Twin
OPIE X

8. • X11
• Desktop Window Manager (MS Windows)
• Quartz Compositor (Mac OS X)
• QWS
• S60 Window Manager

9. Window Surface

10. Surface
Surface

11. Screen

12. Window System

13. Window System

14. Window System Qt Application
IPC #include<QtGui>
int main(int argc, char *argv[])
{
QApplication a(argc,argv);
QWidget w;
w.show();
return a.exec();
}

15. • Widgets and Window Systems
• Window Systems
• Windows and Widgets
• Updates and Painting
• Events and Loops

16. Surface
Surface
Surface

17. Surface
Surface Surface

19. Widget
Window
Widget

20. Window

21. • Widgets and Window Systems
• Window Systems
• Windows and Widgets
• Updates and Painting
• Events and Loops

22. Window System Paint Painting Code
#include<QtGui>
int main(int argc, char
*argv[])
{
QApplication a
(argc,argv);
QWidget w;
w.show();
return a.exec();
}
Update

23. Window System Backing Store Painting Code
#include<QtGui>
int main(int argc, char
*argv[])
{
QApplication a
(argc,argv);
QWidget w;
w.show();
return a.exec();
}

24. Text
Text

25. Text
Text

26. • Client Side
• Top-Level Window
• Backing Store
• Pixmap

27. • Server Side
• Window
• Pixmap

28. • Client Side • Server Side
• Window • Window
• Backing Store • Pixmap
• Pixmap

29. void QWidgetPrivate::drawWidget(QPaintDevice *pdev,
const QRegion &rgn,
const QPoint &offset,
int flags,
QPainter *sharedPainter,
QWidgetBackingStore
*backingStore)
{
...
//actually send the paint event
QPaintEvent e(toBePainted);
QCoreApplication::sendSpontaneousEvent(q, &e);
...
}

30. • Widgets and Window Systems
• Window Systems
• Windows and Widgets
• Updates and Painting
• Events and Loops

31. • Spontaneous Events
• Application Events

32. Input Event bool W::event(QEvent *e)
{
Any if (e->type() == t)
foobar();
return false;
}

33. Window System Socket Qt Event Dispatcher Event Handler
bool
W::event
(QEvent *e)
{
if (e-
>type() ==
Qt Event Loop

34. int QCoreApplication::exec()
{
...
QEventLoop eventLoop;
self->d_func()->in_exec = true;
self->d_func()->aboutToQuitEmitted = false;
int returnCode = eventLoop.exec();
...
}

35. int QEventLoop::exec(ProcessEventsFlags flags)
{
...
try {
while (!d->exit)
processEvents(flags | WaitForMoreEvents
| EventLoopExec);
} catch (...) {
...
--d->threadData->loopLevel;
return d->returnCode;
}

36. bool QEventLoop::processEvents(ProcessEventsFlags flags)
{
Q_D(QEventLoop);
if (!d->threadData->eventDispatcher)
return false;
if (flags & DeferredDeletion)
QCoreApplication::sendPostedEvents(0,
QEvent::DeferredDelete);
return d->threadData->eventDispatcher->processEvents(flags);
}

37. bool QEventDispatcherUNIX::processEvents
(QEventLoop::ProcessEventsFlags flags)
{
...
// we are awake, broadcast it
emit awake();
QCoreApplicationPrivate::sendPostedEvents(0, 0,
d->threadData);
...
nevents = d->doSelect(flags, tm);
...
}

38. int QEventDispatcherUNIXPrivate::doSelect(
QEventLoop::ProcessEventsFlags flags, timeval *timeout)
{
...
// Process timers and socket notifiers - the common UNIX stuff
...
nsel = q->select(highest + 1,
&sn_vec[0].select_fds,
&sn_vec[1].select_fds,
&sn_vec[2].select_fds,
timeout);
...
}

39. int QEventDispatcherUNIX::select(int nfds,
fd_set *readfds,
fd_set *writefds,
fd_set *exceptfds,
timeval *timeout)
{
return qt_safe_select(nfds, readfds, writefds, exceptfds, timeout);
}

40. int qt_safe_select(int nfds,
fd_set *fdread,
fd_set *fdwrite,
fd_set *fdexcept,
const struct timeval *orig_timeout)
{
...
// loop and recalculate the timeout as needed
int ret;
forever {
ret = ::select(nfds, fdread, fdwrite, fdexcept, &timeout);
if (ret != -1 || errno != EINTR)
return ret;
// recalculate the timeout
...
}
}

41. • select()
• poll status of file descriptors
• blocks until timeout

42. X11 Socket XLib Queue Qt Event Dispatcher Event Handler
bool
W::event
(QEvent *e)
{
if (e-
>type() ==
Qt Event Loop

43. postEvent() Qt Event Queue Event Loop Event Handler
#include<Q bool
tGui> W::event
int main(int (QEvent *e)
argc, char {
*argv[]) if (e-
{ >type() ==

44. sendEvent() Event Handler
#include<Q bool
tGui> W::event
int main(int (QEvent *e)
argc, char {
*argv[]) if (e-
{ >type() ==

45. • Event Propagation

46. D
A
C
B

47. D
C
A B

48. D
C
A B

49. D
C
A B

50. D
C
A B

51. bool QApplication::notify(QObject *receiver, QEvent *e)
{
...
bool res = false;
if (!receiver->isWidgetType()) {
res = d->notify_helper(receiver, e);
} else switch (e->type()) {
...
}

52. • Widgets Propagate Events

53. ...
case QEvent::StatusTip:
case QEvent::WhatsThisClicked:
{
QWidget *w = static_cast<QWidget *>(receiver);
while (w) {
res = d->notify_helper(w, e);
if ((res && e->isAccepted()) || w->isWindow())
break;
w = w->parentWidget();
}
}
break;
...

54. • Input Events Are Propagated

55. • Input Events are propagated if
• event->isAccepted() == false
• receiver->event(e) == false

56. bool QCoreApplicationPrivate::notify_helper(QObject *receiver,
QEvent * event)
{
// send to all application event filters
if (sendThroughApplicationEventFilters(receiver, event))
return true;
// send to all receiver event filters
if (sendThroughObjectEventFilters(receiver, event))
return true;
// deliver the event
return receiver->event(event);
}

57. by Dan Queiroz on flickr
Flags and Attributes

58. • Flags and Attributes
• Window Types
• Window Hints
• Widget States
• Widget Attributes

59. • QWidget
• QPaintDevice
• QObject
• QWindowSurface

60. • Flags and Attributes
• Window Types
• Window Hints
• Widget States
• Widget Attributes

61. • Window Types
• Widget
• Window

62. • Dialog
• Sheet (Mac)
• Drawer (Mac)
• Popup
• ToolTip
• SplashScreen
• Desktop
• SubWindow (MDI)

64. • Flags and Attributes
• Window Types
• Window Hints
• Widget States
• Widget Attributes

65. • CustomizeWindowHint • MacWindowToolBarButtonHint
• WindowTitleHint • BypassGraphicsProxyWidget
• WindowSystemMenuHint • WindowShadeButtonHint
• WindowMinimizeButtonHint • WindowStaysOnTopHint
• WindowMaximizeButtonHint • WindowStaysOnBottomHint
• WindowMinMaxButtonHint • WindowOkButtonHint (WinCE)
• WindowCloseButtonHint • WindowCancelButtonHint (WinCE)
• WindowContextHelpButtonHint

66. • Flags and Attributes
• Window Types
• Window Hints
• Widget States
• Widget Attributes

67. • WindowState
• WindowNoState
• WindowMinimized
• WindowMaximized
• WindowFullScreen
• WindowActive

68. • Flags and Attributes
• Window Types
• Window Hints
• Widget States
• Widget Attributes

69. • Qt::Widget Attribute
• 124 Attributes
• setAttribute()
• testAttribute()

70. • Qt::WA_AcceptDrops
• QWidget::setAcceptDrops()

71. by robclimbing on flickr
Tips and Tricks

72. • Qt::WA_StaticContents

73. Exposed
Static Contents
Exposed

74. • Qt::WA_NoSystemBackground

75. • Qt::WA_OpaquePaintEvent

76. • QWidget::autoFillBackground
• Qt::WA_OpaquePaintEvent

78. • QWidget::scroll()
• QWidget::autoFillBackground
• Qt::WA_OpaquePaintEvent

79. Concealed
Scrolled
Exposed

80. • Qt::WA_TranslucentBackground

81. #include <QtGui>
int main(int argc, char *argv[])
{
QApplication app(argc, argv);
QPixmap skin("transparency.png");
QLabel widget;
widget.setPixmap(skin);
widget.setWindowFlags(Qt::Window
|Qt::CustomizeWindowHint
|Qt::FramelessWindowHint);
widget.setAttribute(Qt::WA_TranslucentBackground);
widget.resize(skin.size());
widget.show();
return app.exec();
}

83. by jeff_c on flickr
The Future of Qt Widgets

84. • The story of two APIs ...

85. • QWidget
• Widget Hierarchy
• QGraphicsItem
• Scene Graph

86. • QWidget
• Alien Widgets
• Graphics Effects
• Disable Clipping ?
• Disable Move Events ?
• Transformations ?

87. • Is it possible ?

88. • Is it possible in Qt 4.x ?

89. Thank you!
Questions?

90. Bonus Material

91. Qt Developer Days
Window System

92. Window Surface Scene Graph IPC

93. QSharedMemory QGraphicsScene QTcpSocket

94. • Server
• Window

95. • Server
• Connections
• Scene Graph

96. • Window
• Surface
• Geometry
• Id

97. Server Client
#include<QtGui>
int main(int argc, char *argv[])
{
QApplication a(argc,argv);
QWidget w;
w.show();
return a.exec();
}

98. Server Protocol Client
?
#include<QtGui>
int main(int argc, char *argv[])
{
QApplication a(argc,argv);
QWidget w;
w.show();
return a.exec();
}

99. • Message
• Request
• Reply
• Event

100. Request #include<QtGui>
int main(int argc, char
*argv[])
{
QApplication a
(argc,argv);
QWidget w;
w.show();
return a.exec();
}
Response #include<QtGui>
int main(int argc, char
*argv[])
{
QApplication a
(argc,argv);
QWidget w;
w.show();
return a.exec();
}

101. Event bool W::event(QEvent *e)
{
if (e->type() == t)
foobar();
return false;
}

102. Lighthouse

103. • Research!
• Qt Graphicssystem Interface
• Makes Qt ports easy

104. • QGraphicsSystem
• QGraphicsSystemScreen
• QWindowSurface

105. • QGraphicsSystem
• Window Surfaces
• Server Communication

106. • QGraphicsSystemScreen
• Screen Information
• Depth
• Resolution
• Size

107. • QWindowSurface
• Surface
• Geometry
• Id

108. Demo

109. Source Code
• git://gitorious.org/+qt-developers/qt/lighthouse.git