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><HEAD
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><TITLE
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>Signal and Slot Support</TITLE
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><META
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NAME="GENERATOR"
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CONTENT="Modular DocBook HTML Stylesheet Version 1.7"><LINK
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REL="HOME"
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TITLE="Python Bindings for KDE (PyKDE-3.16.0)"
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HREF="index.html"><LINK
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REL="PREVIOUS"
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TITLE="General Limitations"
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HREF="limits.html"><LINK
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REL="NEXT"
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TITLE="Static Member Functions"
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HREF="static.html"></HEAD
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><BODY
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><TABLE
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SUMMARY="Header navigation table"
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COLSPAN="3"
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ALIGN="center"
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>Python Bindings for KDE (PyKDE-3.16.0)</TH
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></TR
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><TR
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><TD
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><A
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HREF="limits.html"
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ACCESSKEY="P"
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>Prev</A
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></TD
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><TD
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WIDTH="80%"
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VALIGN="bottom"
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VALIGN="bottom"
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>Next</A
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></TD
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></TR
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></TABLE
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><HR
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ALIGN="LEFT"
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WIDTH="100%"></DIV
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><DIV
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><H1
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CLASS="SECT1"
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><A
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NAME="AEN81"
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></A
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>Signal and Slot Support</H1
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="AEN83"
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></A
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>General Signals and Slots</H2
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><P
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>A signal may be either a TQt signal (specified using
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<TT
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CLASS="LITERAL"
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>SIGNAL()</TT
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>) or a Python signal (specified using
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<TT
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CLASS="LITERAL"
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>PYSIGNAL()</TT
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>).</P
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><P
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>A slot can be either a Python callable object, a TQt signal (specified using
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<TT
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CLASS="LITERAL"
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>SIGNAL()</TT
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>), a Python signal (specified using
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<TT
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CLASS="LITERAL"
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>PYSIGNAL()</TT
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>), or a TQt slot (specified using
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<TT
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CLASS="LITERAL"
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>SLOT()</TT
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>).</P
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><P
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>You connect signals to slots (and other signals) as you would from C++. For
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example:</P
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><TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><PRE
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CLASS="PROGRAMLISTING"
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>TQObject.connect(a,SIGNAL("TQtSig()"),pyFunction)
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TQObject.connect(a,SIGNAL("TQtSig()"),pyClass.pyMethod)
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TQObject.connect(a,SIGNAL("TQtSig()"),PYSIGNAL("PySig"))
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TQObject.connect(a,SIGNAL("TQtSig()"),SLOT("TQtSlot()"))
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TQObject.connect(a,PYSIGNAL("PySig"),pyFunction)
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TQObject.connect(a,PYSIGNAL("PySig"),pyClass.pyMethod)
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TQObject.connect(a,PYSIGNAL("PySig"),SIGNAL("TQtSig()"))
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TQObject.connect(a,PYSIGNAL("PySig"),SLOT("TQtSlot()"))</PRE
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></TD
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></TR
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></TABLE
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><P
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>When a slot is a Python method that corresponds to a TQt slot then a signal can
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be connected to either the Python method or the TQt slot. The following
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connections achieve the same effect.</P
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><TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><PRE
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CLASS="PROGRAMLISTING"
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>sbar = TQScrollBar()
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lcd = TQLCDNumber()
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TQObject.connect(sbar,SIGNAL("valueChanged(int)"),lcd.display)
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TQObject.connect(sbar,SIGNAL("valueChanged(int)"),lcd,SLOT("display(int)"))</PRE
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></TD
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></TR
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></TABLE
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><P
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>The difference is that the second connection is made at the C++ level and is
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more efficient.</P
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><P
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>Disconnecting signals works in exactly the same way.</P
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><P
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>Any instance of a class that is derived from the <TT
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CLASS="LITERAL"
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>TQObject</TT
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>
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class can emit a signal using the <TT
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CLASS="LITERAL"
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>emit</TT
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> method. This takes
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two arguments. The first is the Python or TQt signal, the second is a Python
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tuple which are the arguments to the signal. For example:</P
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><TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><PRE
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CLASS="PROGRAMLISTING"
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>a.emit(SIGNAL("clicked()"),())
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a.emit(PYSIGNAL("pySig"),("Hello","World"))</PRE
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></TD
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></TR
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></TABLE
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><P
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>TQt allows a signal to be connected to a slot that requires fewer arguments than
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the signal passes. The extra arguments are tquietly discarded. Python slots
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can be used in the same way.</P
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></DIV
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><DIV
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CLASS="SECT2"
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><H2
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CLASS="SECT2"
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><A
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NAME="AEN103"
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></A
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>Slots in Menus, Toolbars and Actions</H2
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><P
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>The C++ declarations for menu items or KActions are similar to these examples:</P
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><TABLE
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BORDER="0"
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WIDTH="100%"
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><TD
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><PRE
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CLASS="PROGRAMLISTING"
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>int TQMenuData::insertItem (const TQString & text,
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const TQObject * receiver, const char * member,
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int accel = 0, int id = -1, int index = -1 )
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KAction ( const TQString& text, int accel,
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const TQObject* receiver, const char* slot,
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TQObject* parent, const char* name = 0 )</PRE
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></TD
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></TR
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></TABLE
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><P
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>Notice the "const TQObject* receiver, const char* slot" parameters for each declaration.</P
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><P
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>In PyKDE, these two parameters are replaced with a SINGLE parameter that specifies the
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slot to be connected to the menu item, toolbar button or KAction:</P
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><TABLE
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BORDER="0"
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BGCOLOR="#E0E0E0"
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WIDTH="100%"
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><TR
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><TD
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><PRE
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CLASS="PROGRAMLISTING"
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>p = insertItem ("Open", self.slotOpen, 0, -1, -1)
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action = KAction ("Open", 0, self.slotOpen, None, 0)</PRE
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></TD
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></TR
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></TABLE
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><P
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>This substitution applies to appropriate methods in KStdAction, KAction and related
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subclasses, KAccelMenu and KToolBar</P
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></DIV
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></DIV
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><HR
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SUMMARY="Footer navigation table"
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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><A
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HREF="limits.html"
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ACCESSKEY="P"
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>Prev</A
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></TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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><A
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HREF="index.html"
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ACCESSKEY="H"
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>Home</A
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></TD
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><TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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><A
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HREF="static.html"
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ACCESSKEY="N"
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>Next</A
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></TD
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></TR
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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>General Limitations</TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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VALIGN="top"
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> </TD
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WIDTH="33%"
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ALIGN="right"
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VALIGN="top"
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>Static Member Functions</TD
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></TR
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></TABLE
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></DIV
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></BODY
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></HTML
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>
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