--- loncom/interface/loncommon.pm	2003/08/20 18:18:45	1.112
+++ loncom/interface/loncommon.pm	2003/08/26 17:20:45	1.113
@@ -1,7 +1,7 @@
 # The LearningOnline Network with CAPA
 # a pile of common routines
 #
-# $Id: loncommon.pm,v 1.112 2003/08/20 18:18:45 bowersj2 Exp $
+# $Id: loncommon.pm,v 1.113 2003/08/26 17:20:45 bowersj2 Exp $
 #
 # Copyright Michigan State University Board of Trustees
 #
@@ -624,8 +624,6 @@ sub helpLatexCheatsheet {
 Translate $text to allow it to be output as a 'comma seperated values' 
 format.
 
-=back
-
 =cut
 
 sub csv_translate {
@@ -635,6 +633,91 @@ sub csv_translate {
     return $text;
 }
 
+=pod
+
+=item * change_content_javascript():
+
+This and the next function allow you to create small sections of an
+otherwise static HTML page that you can update on the fly with
+Javascript, even in Netscape 4.
+
+The Javascript fragment returned by this function (no E<lt>scriptE<gt> tag)
+must be written to the HTML page once. It will prove the Javascript
+function "change(name, content)". Calling the change function with the
+name of the section 
+you want to update, matching the name passed to C<changable_area>, and
+the new content you want to put in there, will put the content into
+that area.
+
+B<Note>: Netscape 4 only reserves enough space for the changable area
+to contain room for the original contents. You need to "make space"
+for whatever changes you wish to make, and be B<sure> to check your
+code in Netscape 4. This feature in Netscape 4 is B<not> powerful;
+it's adequate for updating a one-line status display, but little more.
+This script will set the space to 100% width, so you only need to
+worry about height in Netscape 4.
+
+Modern browsers are much less limiting, and if you can commit to the
+user not using Netscape 4, this feature may be used freely with
+pretty much any HTML.
+
+=cut
+
+sub change_content_javascript {
+    # If we're on Netscape 4, we need to use Layer-based code
+    if ($ENV{'browser.type'} eq 'netscape' &&
+	$ENV{'browser.version'} =~ /^4\./) {
+	return (<<NETSCAPE4);
+	function change(name, content) {
+	    doc = document.layers[name+"___escape"].layers[0].document;
+	    doc.open();
+	    doc.write(content);
+	    doc.close();
+	}
+NETSCAPE4
+    } else {
+	# Otherwise, we need to use semi-standards-compliant code
+	# (technically, "innerHTML" isn't standard but the equivalent
+	# is really scary, and every useful browser supports it
+	return (<<DOMBASED);
+	function change(name, content) {
+	    element = document.getElementById(name);
+	    element.innerHTML = content;
+	}
+DOMBASED
+    }
+}
+
+=pod
+
+=item * changable_area($name, $origContent):
+
+This provides a "changable area" that can be modified on the fly via
+the Javascript code provided in C<change_content_javascript>. $name is
+the name you will use to reference the area later; do not repeat the
+same name on a given HTML page more then once. $origContent is what
+the area will originally contain, which can be left blank.
+
+=cut
+
+sub changable_area {
+    my ($name, $origContent) = @_;
+
+    if ($ENV{'browser.type'} eq 'netscape' &&
+	$ENV{'browser.version'} =~ /^4\./) {
+	# If this is netscape 4, we need to use the Layer tag
+	return "<ilayer width='100%' id='${name}___escape' overflow='none'><layer width='100%' id='$name' overflow='none'>$origContent</layer></ilayer>";
+    } else {
+	return "<span id='$name'>$origContent</span>";
+    }
+}
+
+=pod
+
+=back
+
+=cut
+
 ###############################################################
 ##        Home server <option> list generating code          ##
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