Qt Tutorial Notes

source : http://code.google.com/p/mixtools/source/browse/#svn/trunk/qt/tutorial/tutorial
http://doc.trolltech.com/4.3/tutorial.html

T4:

• qApp is a global variable
• Put widget on heap, so Qt can manage the memory for you

T5:

• treat layout as the parent of widgets being enclosed
• How to overflow?

T6:

• Remember to show() the widget
• setLayout() takes a "pointer" as the argument
• qRand() returns a value between 0 and RAND_MAX (defined in and )
• check out more global variable in Qt: http://doc.trolltech.com/4.2/qtglobal.html
  

T7:

• Signal can connect to signal: so you fire another signal.
• Two ways to fire a signal: 1. signal connect to signal 2. directly fire it with emit
  
• Cannot treat signal as slot
• Signal is automatically generated by MOC (meta-object compiler), so do not implement it yourself, or you will get duplicate definition.
  
• The Q_OBJECT macro must be used in all subclass of QObject, or the signal/slot will not work. Put the Q_OBJECT in the header file, and put the .h file in .pro file. This way qmake can search source and header files for the Q_Object macro. It will generate build instruction for moc.
• slots can be public, protected, and private
• To declare signal, just do "signals:"
  

T8:

• setFocus()
• setFocusProxy()
• QString::Number() convert number to string
• use "&" to set the button shortcut with Alt

T9:

• Understand The Coordinate System of Qt
• QRect: upper-left + width + height
• drawPie: 0 is 3 o'clock, and draws counter-clockwise
• QPainter::rotate(): on coordinate, and counter-clockwise
• QTimer::start(int millisecs interval), stop(), isActive()

• QTimer::singleShot(600000, &app, SLOT(quit()));
  

T11:

• Understand save() and restore()