Support for external markdown files, including configurable (vertical) slide separator

plugin/markdown/markdown.js

@@ -6,11 +6,7 @@
         throw 'The reveal.js Markdown plugin requires Showdown to be loaded';
     }
 
-    var sections = document.querySelectorAll( '[data-markdown]' );
-
-    for( var i = 0, len = sections.length; i < len; i++ ) {
-        var section = sections[i];
-        var notes = section.querySelector( 'aside.notes' );
+    var stripLeadingWhitespace = function(section) {
 
         var template = section.querySelector( 'script' );
 
@@ -27,11 +23,125 @@
             text = text.replace( new RegExp('\\n? {' + leadingWs + '}','g'), '\n' );
         }
 
-        section.innerHTML = (new Showdown.converter()).makeHtml(text);
+        return text;
+
+    };
+
+    var slidifyMarkdown = function(markdown, separator, vertical) {
+
+        separator = separator || '^\n---\n$';
+
+        var reSeparator = new RegExp(separator + (vertical ? '|' + vertical : ''), 'mg'),
+            reHorSeparator = new RegExp(separator),
+            matches,
+            lastIndex = 0,
+            isHorizontal,
+            wasHorizontal = true,
+            content,
+            sectionStack = [],
+            markdownSections = '';
+
+        // iterate until all blocks between separators are stacked up
+        while( matches = reSeparator.exec(markdown) ) {
+
+            // determine direction (horizontal by default)
+            isHorizontal = reHorSeparator.test(matches[0]);
+
+            if( !isHorizontal && wasHorizontal ) {
+                // create vertical stack
+                sectionStack.push([]);
+            }
+
+            // pluck slide content from markdown input
+            content = markdown.substring(lastIndex, matches.index);
+
+            if( isHorizontal && wasHorizontal ) {
+                // add to horizontal stack
+                sectionStack.push(content);
+            } else {
+                // add to vertical stack
+                sectionStack[sectionStack.length-1].push(content);
+            }
+
+            lastIndex = reSeparator.lastIndex;
+            wasHorizontal = isHorizontal;
+
+        }
+
+        // add the remaining slide
+        (wasHorizontal ? sectionStack : sectionStack[sectionStack.length-1]).push(markdown.substring(lastIndex));
+
+        // flatten the hierarchical stack, and insert <section data-markdown> tags
+        for( var k = 0, klen = sectionStack.length; k < klen; k++ ) {
+            markdownSections += typeof sectionStack[k] === 'string'
+                ? '<section data-markdown>' + sectionStack[k] + '</section>'
+                : '<section><section data-markdown>' + sectionStack[k].join('</section><section data-markdown>') + '</section></section>';
+        }
+
+        return markdownSections;
+    };
+
+    var queryMarkdownSlides = function() {
+
+        var sections = document.querySelectorAll( '[data-markdown]'),
+            section;
+
+        for( var j = 0, jlen = sections.length; j < jlen; j++ ) {
+
+            section = sections[j];
+
+            if( section.getAttribute('data-markdown').length ) {
+
+                var xhr = new XMLHttpRequest(),
+                    url = section.getAttribute('data-markdown');
+
+                xhr.onreadystatechange = function () {
+                    if( xhr.readyState === 4 ) {
+                        section.outerHTML = slidifyMarkdown( xhr.responseText, section.getAttribute('data-separator'), section.getAttribute('data-vertical') );
+                    }
+                };
+
+                xhr.open('GET', url, false);
+                xhr.send();
+
+            } else if( section.getAttribute('data-separator') ) {
+
+                var markdown = stripLeadingWhitespace(section);
+                section.outerHTML = slidifyMarkdown( markdown, section.getAttribute('data-separator'), section.getAttribute('data-vertical') );
+
+            }
+        }
+
+        querySlides();
+
+    };
+
+    var querySlides = function() {
+
+        var sections = document.querySelectorAll( '[data-markdown]');
+
+        for( var j = 0, jlen = sections.length; j < jlen; j++ ) {
+
+            makeHtml(sections[j]);
+
+        }
+
+    };
+
+    var makeHtml = function(section) {
+
+        var notes = section.querySelector( 'aside.notes' );
+
+        var markdown = stripLeadingWhitespace(section);
+
+        section.innerHTML = (new Showdown.converter()).makeHtml(markdown);
 
         if( notes ) {
             section.appendChild( notes );
         }
-    }
 
-})();
+    };
+
+    queryMarkdownSlides();
+
+})();