added idle clear timer

index.html

@@ -286,8 +286,7 @@ function keyboard_entry(ev) {
     toggle_blank();
   }
   if (/C/.test(k)) {
-    document.getElementById("filter").value='';
-    filter(ev);
+    clear();
   }
 }
 
@@ -426,8 +425,23 @@ function set_cookie(name,value) {
   document.cookie = name + "=" + value.toString() + "&" + window.location.pathname +
    ";path=" + window.location.pathname + ";max-age="+ (60*60*2).toString() + ";";
 }
-document.onkeyup=keyboard_entry;
-document.onscroll=scroll_save;
+
+function clear() {
+  document.getElementById("filter").value = '';
+  filter(true);
+}
+function resetTimer() {
+  clearTimeout(idleTimer);
+  idleTimer = setTimeout(clear, 20 * 60 * 1000);  // 20 minutes
+}
+var idleTimer;
+
+window.onload = resetTimer;
+document.onmousemove = resetTimer;
+document.onmouseclick = resetTimer;
+document.onkeypress = resetTimer;
+document.onkeyup = keyboard_entry;
+document.onscroll = scroll_save;
 var linkReg=/([^\[]*)\[([^\]]+)\]\(([^\)]+)\)(.*)/;
 var linkPlain=/(.*)(http[^\s]+)(.*)/;
 var linkList=[];