# HG changeset patch
# User Adam Chlipala <adamc@hcoop.net>
# Date 1241547355 14400
# Node ID c9c76aeaae64b3a44b3e95c7cfcdd19f13b12641
# Parent  fc3db9e0f0f67dbd24c9f1fa2e2151cd98b9536f
on* handlers

diff -r fc3db9e0f0f6 -r c9c76aeaae64 doc/manual.tex
--- a/doc/manual.tex	Tue May 05 13:21:26 2009 -0400
+++ b/doc/manual.tex	Tue May 05 14:15:55 2009 -0400
@@ -1621,10 +1621,13 @@
 $$\begin{array}{l}
   \mt{val} \; \mt{tag} : \mt{attrsGiven} ::: \{\mt{Type}\} \to \mt{attrsAbsent} ::: \{\mt{Type}\} \to \mt{ctxOuter} ::: \{\mt{Unit}\} \to \mt{ctxInner} ::: \{\mt{Unit}\} \\
   \hspace{.1in} \to \mt{useOuter} ::: \{\mt{Type}\} \to \mt{useInner} ::: \{\mt{Type}\} \to \mt{bindOuter} ::: \{\mt{Type}\} \to \mt{bindInner} ::: \{\mt{Type}\} \\
-  \hspace{.1in} \to \lambda [\mt{attrsGiven} \sim \mt{attrsAbsent}] \; [\mt{useOuter} \sim \mt{useInner}] \; [\mt{bindOuter} \sim \mt{bindInner}] \Rightarrow \$\mt{attrsGiven} \\
+  \hspace{.1in} \to \lambda [\mt{attrsGiven} \sim \mt{attrsAbsent}] \; [\mt{useOuter} \sim \mt{useInner}] \; [\mt{bindOuter} \sim \mt{bindInner}] \\
+  \hspace{.1in} \Rightarrow \mt{option} \; \mt{css\_class} \\
+  \hspace{.1in} \to \$\mt{attrsGiven} \\
   \hspace{.1in} \to \mt{tag} \; (\mt{attrsGiven} \rc \mt{attrsAbsent}) \; \mt{ctxOuter} \; \mt{ctxInner} \; \mt{useOuter} \; \mt{bindOuter} \\
   \hspace{.1in} \to \mt{xml} \; \mt{ctxInner} \; \mt{useInner} \; \mt{bindInner} \to \mt{xml} \; \mt{ctxOuter} \; (\mt{useOuter} \rc \mt{useInner}) \; (\mt{bindOuter} \rc \mt{bindInner})
 \end{array}$$
+Note that any tag may be assigned a CSS class.  This is the sole way of making use of the values produced by $\mt{style}$ declarations.  Ur/Web itself doesn't deal with the syntax or semantics of style sheets; they can be linked via URLs with \texttt{link} tags.  However, Ur/Web does make it easy to calculate upper bounds on usage of CSS classes through program analysis.
 
 Two XML fragments may be concatenated.
 $$\begin{array}{l}
@@ -1668,6 +1671,15 @@
   \mt{val} \; \mt{sleep} : \mt{int} \to \mt{transaction} \; \mt{unit}
 \end{array}$$
 
+A few functions are available to registers callbacks for particular error events.  Respectively, they are triggered on calls to $\mt{error}$, uncaught JavaScript exceptions, failure of remote procedure calls, the severance of the connection serving asynchronous messages, or the occurrence of some other error with that connection.  If no handlers are registered for a kind of error, then occurrences of that error are ignored silently.
+$$\begin{array}{l}
+  \mt{val} \; \mt{onError} : (\mt{xbody} \to \mt{transaction} \; \mt{unit}) \to \mt{transaction} \; \mt{unit} \\
+  \mt{val} \; \mt{onFail} : (\mt{string} \to \mt{transaction} \; \mt{unit}) \to \mt{transaction} \; \mt{unit} \\
+  \mt{val} \; \mt{onConnectFail} : \mt{transaction} \; \mt{unit} \to \mt{transaction} \; \mt{unit} \\
+  \mt{val} \; \mt{onDisconnect} : \mt{transaction} \; \mt{unit} \to \mt{transaction} \; \mt{unit} \\
+  \mt{val} \; \mt{onServerError} : (\mt{string} \to \mt{transaction} \; \mt{unit}) \to \mt{transaction} \; \mt{unit}
+\end{array}$$
+
 \subsubsection{Functional-Reactive Page Generation}
 
 Most approaches to ``AJAX''-style coding involve imperative manipulation of the DOM tree representing an HTML document's structure.  Ur/Web follows the \emph{functional-reactive} approach instead.  Programs may allocate mutable \emph{sources} of arbitrary types, and an HTML page is effectively a pure function over the latest values of the sources.  The page is not mutated directly, but rather it changes automatically as the sources are mutated.