<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >By the way, what are the differences between signals and events?</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REL="HOME" TITLE="GTK+ FAQ" HREF="book1.html"><LINK REL="UP" TITLE="Development with GTK+: general questions" HREF="c466.html"><LINK REL="PREVIOUS" TITLE="How do I catch a double click event? [GTK 2.x]" HREF="x535.html"><LINK REL="NEXT" TITLE="Data I pass to the delete_event (or other event) handler gets corrupted." HREF="x557.html"></HEAD ><BODY CLASS="SECT1" BGCOLOR="#FFFFFF" TEXT="#000000" LINK="#0000FF" VLINK="#840084" ALINK="#0000FF" ><DIV CLASS="NAVHEADER" ><TABLE SUMMARY="Header navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TH COLSPAN="3" ALIGN="center" >GTK+ FAQ</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="x535.html" ACCESSKEY="P" ><<< Previous</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" >Development with GTK+: general questions</TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="x557.html" ACCESSKEY="N" >Next >>></A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="AEN546" >By the way, what are the differences between signals and events?</A ></H1 ><P >First of all, Havoc Pennington gives a rather complete description of the differences between events and signals in his free book (two chapters can be found at <A HREF="http://www106.pair.com/rhp/sample_chapters.html" TARGET="_top" >http://www106.pair.com/rhp/sample_chapters.html</A >).</P ><P >Moreover, Havoc posted this to the <TT CLASS="LITERAL" >gtk-list</TT > <SPAN CLASS="QUOTE" >"Events are a stream of messages received from the X server. They drive the Gtk main loop; which more or less amounts to "wait for events, process them" (not exactly, it is really more general than that and can wait on many different input streams at once). Events are a Gdk/Xlib concept."</SPAN ></P ><P ><SPAN CLASS="QUOTE" >"Signals are a feature of GtkObject and its subclasses. They have nothing to do with any input stream; really a signal is just a way to keep a list of callbacks around and invoke them ("emit" the signal). There are lots of details and extra features of course. Signals are emitted by object instances, and are entirely unrelated to the Gtk main loop. Conventionally, signals are emitted "when something changes" about the object emitting the signal."</SPAN ></P ><P ><SPAN CLASS="QUOTE" >"Signals and events only come together because GtkWidget happens to emit signals when it gets events. This is purely a convenience, so you can connect callbacks to be invoked when a particular widget receives a particular event. There is nothing about this that makes signals and events inherently related concepts, any more than emitting a signal when you click a button makes button clicking and signals related concepts."</SPAN ></P ></DIV ><DIV CLASS="NAVFOOTER" ><HR ALIGN="LEFT" WIDTH="100%"><TABLE SUMMARY="Footer navigation table" WIDTH="100%" BORDER="0" CELLPADDING="0" CELLSPACING="0" ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" ><A HREF="x535.html" ACCESSKEY="P" ><<< Previous</A ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="book1.html" ACCESSKEY="H" >Home</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" ><A HREF="x557.html" ACCESSKEY="N" >Next >>></A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >How do I catch a double click event? <I CLASS="EMPHASIS" >[GTK 2.x]</I ></TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" ><A HREF="c466.html" ACCESSKEY="U" >Up</A ></TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Data I pass to the <TT CLASS="LITERAL" >delete_event</TT > (or other event) handler gets corrupted.</TD ></TR ></TABLE ></DIV ></BODY ></HTML >