<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01//EN" "http://www.w3.org/TR/html4/loose.dtd"> <HTML ><HEAD ><TITLE >Drag-and-drop (DND)</TITLE ><META NAME="GENERATOR" CONTENT="Modular DocBook HTML Stylesheet Version 1.79"><LINK REL="HOME" TITLE="GTK+ 2.0 Tutorial" HREF="book1.html"><LINK REL="PREVIOUS" TITLE="Supplying the selection" HREF="x1873.html"><LINK REL="NEXT" TITLE="Properties" HREF="x1921.html"></HEAD ><BODY CLASS="CHAPTER" 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+ 2.0 Tutorial</TH ></TR ><TR ><TD WIDTH="10%" ALIGN="left" VALIGN="bottom" ><A HREF="x1873.html" ACCESSKEY="P" ><<< Previous</A ></TD ><TD WIDTH="80%" ALIGN="center" VALIGN="bottom" ></TD ><TD WIDTH="10%" ALIGN="right" VALIGN="bottom" ><A HREF="x1921.html" ACCESSKEY="N" >Next >>></A ></TD ></TR ></TABLE ><HR ALIGN="LEFT" WIDTH="100%"></DIV ><DIV CLASS="CHAPTER" ><H1 ><A NAME="CH-DRAGANGDROP" ></A >Drag-and-drop (DND)</H1 ><P >GTK+ has a high level set of functions for doing inter-process communication via the drag-and-drop system. GTK+ can perform drag-and-drop on top of the low level Xdnd and Motif drag-and-drop protocols.</P ><DIV CLASS="SECT1" ><H1 CLASS="SECT1" ><A NAME="SEC-DRAGANDDROPOVERVIEW" >Overview</A ></H1 ><P >An application capable of GTK+ drag-and-drop first defines and sets up the GTK+ widget(s) for drag-and-drop. Each widget can be a source and/or destination for drag-and-drop. Note that these GTK+ widgets must have an associated X Window, check using GTK_WIDGET_NO_WINDOW(widget)).</P ><P >Source widgets can send out drag data, thus allowing the user to drag things off of them, while destination widgets can receive drag data. Drag-and-drop destinations can limit who they accept drag data from, e.g. the same application or any application (including itself).</P ><P >Sending and receiving drop data makes use of GTK+ signals. Dropping an item to a destination widget requires both a data request (for the source widget) and data received signal handler (for the target widget). Additional signal handers can be connected if you want to know when a drag begins (at the very instant it starts), to when a drop is made, and when the entire drag-and-drop procedure has ended (successfully or not).</P ><P >Your application will need to provide data for source widgets when requested, that involves having a drag data request signal handler. For destination widgets they will need a drop data received signal handler. </P ><P >So a typical drag-and-drop cycle would look as follows:</P ><P ></P ><OL TYPE="1" ><LI ><P > Drag begins.</P ></LI ><LI ><P > Drag data request (when a drop occurs).</P ></LI ><LI ><P > Drop data received (may be on same or different application).</P ></LI ><LI ><P > Drag data delete (if the drag was a move).</P ></LI ><LI ><P > Drag-and-drop procedure done.</P ></LI ></OL ><P >There are a few minor steps that go in between here and there, but we will get into detail about that later.</P ></DIV ></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="x1873.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="x1921.html" ACCESSKEY="N" >Next >>></A ></TD ></TR ><TR ><TD WIDTH="33%" ALIGN="left" VALIGN="top" >Supplying the selection</TD ><TD WIDTH="34%" ALIGN="center" VALIGN="top" > </TD ><TD WIDTH="33%" ALIGN="right" VALIGN="top" >Properties</TD ></TR ></TABLE ></DIV ></BODY ></HTML >
