Add onSinglePageLoading event; allow skipping pages in onSinglePageLoaded

lib/Pico.php

@@ -1017,6 +1017,9 @@ class Pico
 
             $id = substr($file, $contentDirLength, -$contentExtLength);
 
+            // trigger onSinglePageLoading event
+            $this->triggerEvent('onSinglePageLoading', array(&$id));
+
             // drop inaccessible pages (e.g. drop "sub.md" if "sub/index.md" exists)
             $conflictFile = $contentDir . $id . '/index' . $contentExt;
             if (in_array($conflictFile, $files, true)) {
@@ -1061,12 +1064,14 @@ class Pico
 
             unset($rawContent, $meta);
 
-            // trigger event
+            // trigger onSinglePageLoaded event
             $this->triggerEvent('onSinglePageLoaded', array(&$page));
 
+            if ($page !== null) {
                 $this->pages[$id] = $page;
             }
         }
+    }
 
     /**
      * Sorts all pages known to Pico