Update documentation to contain DND stuff.

I am missing a decent Linux machine. Could someone please check
if DND works smoothly on those machines?

Just run the 'Input' test and mark and drag text out of the
text widgets into another app. Then drag'n'drop text into the FLTK
widgets. Finally drag text from one widget into another widget
within the same FLTK app.


git-svn-id: file:///fltk/svn/fltk/branches/branch-1.1@1972 ea41ed52-d2ee-0310-a9c1-e6b18d33e121

documentation/subclassing.html

@@ -362,6 +362,7 @@ positions you might want to call <TT>child-&gt;draw_label(x,y,w,h,a)</TT>.
 should call this on all the children if your own damage is equal to
 FL_DAMAGE_CHILD.  Nothing is done if the child is not <TT>visible()</TT>
  or if it is clipped.
+
 <H2>Cut and Paste Support</H2>
 FLTK provides routines to cut and paste 8-bit text (in the future this
 may be UTF-8) between applications:
@@ -372,6 +373,24 @@ may be UTF-8) between applications:
 </UL>
 It may be possible to cut/paste non-text data by using <A href=osissues.html#add_handler>
 <TT>Fl::add_handler()</TT></A>.
+
+<H2>Drag And Drop Support</H2>
+
+FLTK provides routines to drag and drop 8-bit text between applications:
+
+<P>Drag'n'drop operations are are initiated by copying data to the 
+clipboard and calling the function
+<A href="Fl.html#Fl.dnd"><TT>Fl::dnd()</TT></A>.
+
+<P>Drop attempts are handled via <A href="events.html#dnd">events</A>:
+<UL>
+<LI><TT>FL_DND_ENTER</TT></LI>
+<LI><TT>FL_DND_DRAG</TT></LI>
+<LI><TT>FL_DND_LEAVE</TT></LI>
+<LI><TT>FL_DND_RELEASE</TT></LI>
+<LI><TT>FL_PASTE</TT></LI>
+</UL>
+
 <H2>Making a subclass of Fl_Window</H2>
 
 <P>You may want your widget to be a subclass of