diff --git a/demo/demo.js b/demo/demo.js
index eb227809..1291db1a 100644
--- a/demo/demo.js
+++ b/demo/demo.js
@@ -149,6 +149,7 @@ exports.launch = function(env) {
 
     // BEGING TESTING
     var Range = require("ace/range").Range;
+    docs.js.addFold(new Range(0, 13, 0, 18), "args...");
     docs.js.addFold(new Range(1, 10, 2, 10), "foo...");
     docs.js.addFold(new Range(2, 20, 2, 25), "bar...");
     window.s = docs.js;
diff --git a/lib/ace/edit_session.js b/lib/ace/edit_session.js
index 117ae04b..a82b050d 100644
--- a/lib/ace/edit_session.js
+++ b/lib/ace/edit_session.js
@@ -22,6 +22,7 @@
  * Contributor(s):
  *      Fabian Jakobs <fabian AT ajax DOT org>
  *      Mihai Sucan <mihai DOT sucan AT gmail DOT com>
+ *      Julian Viereck <julian DOT viereck AT gmail DOT com>
  *
  * Alternatively, the contents of this file may be used under the terms of
  * either the GNU General Public License Version 2 or later (the "GPL"), or
@@ -55,6 +56,7 @@ var EditSession = function(text, mode) {
     this.$backMarkers = {};
     this.$markerId = 1;
     this.$wrapData = [];
+    this.$foldData = [];
 
     if (text instanceof Document) {
         this.setDocument(text);
@@ -875,8 +877,8 @@ var EditSession = function(text, mode) {
         if (len != 0) {
             if (action.indexOf("remove") != -1) {
                 useWrapMode && this.$wrapData.splice(firstRow, len);
-                // TODO: More checking needed here.
-                this.$foldData.splice(firstRow, len);
+                // TODO: Remove no longer needed folds here.
+                // TODO: Update row data on folds.
                 lastRow = firstRow;
             } else {
                 var args;
@@ -886,10 +888,8 @@ var EditSession = function(text, mode) {
                     this.$wrapData.splice.apply(this.$wrapData, args);
                 }
 
-                args = [firstRow, 0];
-                for (var i = 0; i < len; i++) args.push(false);
-                // TODO: More checking needed here.
-                this.$foldData.splice.apply(this.$foldData, args);
+                // TODO: Expand folds here if needed.
+                // TODO: Update row data on folds.
             }
         }
 
@@ -1041,7 +1041,7 @@ var EditSession = function(text, mode) {
 				screenColumn += 1;
 			}
 		}
-		
+
 		return screenColumn;
     }
 
@@ -1242,7 +1242,7 @@ var EditSession = function(text, mode) {
         return this.documentToScreenPosition(docRow, docColumn).row;
     }
 
-    this.$buildWrappedTextLine = function(row, endRow, endColumn) {
+    this.$buildFoldedTextLine = function(row, endRow, endColumn) {
         var textLine = "";
 
         // Build a one line string for the current fold sequence that starts
@@ -1273,6 +1273,13 @@ var EditSession = function(text, mode) {
                     }
                 }
                 textLine += line.substring(lastEnd, fold.start.column);
+
+                // Stop if the end position is inside of this fold.
+                if (endRow < fold.end.row ||
+                    endRow == fold.end.row && endColumn < fold.end.column
+                ) {
+                    break while_loop;
+                }
                 textLine += fold.placeholder;
                 if (fold.sameLine) {
                     lastEnd = fold.end.column;
@@ -1333,8 +1340,10 @@ var EditSession = function(text, mode) {
             textLine = this.getLine(docRow).substring(0, docColumn);
             foldStartRow = docRow;
         } else {
-            textLine = this.$buildWrappedTextLine(
-                (foldStartRow != null ? foldStartRow : docRow), docRow, docColumn);
+            textLine = this.$buildFoldedTextLine(
+                (foldStartRow != null ? foldStartRow : docRow),
+                docRow,
+                docColumn);
         }
 
         // Clamp textLine if in wrapMode.
@@ -1381,7 +1390,13 @@ var EditSession = function(text, mode) {
             }
         }
 
-        screenRows -= this.getFoldedRowLength(0, length - 1);
+        var foldData = this.$foldData;
+        for (var i = 0; i < foldData.length; i++) {
+            var foldRow = foldData[i];
+            if (foldRow.linkOut) {
+                screenRows -= foldRow.linkOut.end.row - foldRow.linkOut.start.row;
+            }
+        }
         return screenRows;
     }
 
@@ -1438,35 +1453,86 @@ var EditSession = function(text, mode) {
         this.sameLine = range.start.row == range.end.row;
     }
 
+    function FoldRow(row) {
+        this.row = row;
+        this.linkIn = null;
+        this.linkOut = null;
+        this.inRow = [];
+    }
+
+    (function() {
+        this.addInRowFold = function(fold) {
+            if (!fold.sameLine || fold.start.row != this.row) {
+                throw "NOPE: Can't add fold here!";
+            }
+            this.inRow.push(fold);
+            this.inRow.sort(function(a, b) {
+               return a.start.column - b.start.column;
+            });
+        }
+
+        this.addFold = function(fold) {
+            if (fold.sameLine) {
+                this.addInRowFold(fold)
+            } else if (fold.start.row == this.row) {
+                if (this.linkOut) {
+                    throw "There is already a linkOut fold";
+                }
+                this.linkOut = fold;
+            } else if (fold.end.row == this.row) {
+                if (this.linkIn) {
+                    throw "There is already a linkIn fold";
+                }
+                this.linkIn = fold;
+            } else {
+                throw "Trying to add fold to FoldRow that doesn't have a matching row";
+            }
+        }
+    }).call(FoldRow.prototype);
+
+    this.getFoldRow = function(docRow, startFoldRow) {
+        var foldData = this.$foldData;
+        for (var i = foldData.indexOf(startFoldRow) || 0; i < foldData.length; i++) {
+            var foldRow = foldData[i];
+            if (foldRow.row == docRow) {
+                return foldRow;
+            } else if (foldRow.row > docRow) {
+                return null;
+            }
+        }
+        return null;
+    }
+
+    this.getFoldRowOrCreate = function(docRow, startFoldRow) {
+        var foldRow = this.getFoldRow(docRow, startFoldRow);
+        if (!foldRow) {
+            foldRow = new FoldRow(startRow);
+            this.$foldData.push(foldRow);
+            this.$foldData.sort(function(a, b) {
+                return a.row - b.row;
+            });
+        }
+    }
+
     /**
      * Adds a new fold.
      */
     this.addFold = function(range, placeholder) {
         var startRow = range.start.row,
             endRow   = range.end.row,
-            foldData = this.$foldData;
+            foldData = this.$foldData,
+            foldRow  = null;
 
-        // In case there is no fold data for the start row yet.
-        if (!Array.isArray(foldData[startRow])) {
-            foldData[startRow] = [];
-        }
+        foldRow = this.getFoldRowOrCreate(startRow);
 
         var fold = new Fold(range, placeholder);
-        // TODO: The folds have to be ordered by range.start!
-        foldData[startRow].push(fold);
+        foldRow.addFold(fold);
 
-        // Mark all lines folded by this fold as folded.
-        for (var row = startRow + 1; row < endRow; row++) {
-            foldData[row] = fold;
-        }
-
-        // If this fold folds more then one line, then add the fold at the
-        // beginning of the foldData[endRow] as well.
+        // If this fold folds more then one line, then add this fold as the
+        // linkOut of the FoldRow at endRow.
         if (!fold.sameLine) {
-            if (!Array.isArray(foldData[endRow])) {
-                foldData[endRow] = [];
-            }
-            foldData[endRow].splice(0, 0, fold);
+            foldRow = this.getFoldRowOrCreate(endRow, foldRow);
+            foldRow.addFold(fold);
         }
 
         // TODO: Recalculate wrapData
@@ -1481,104 +1547,60 @@ var EditSession = function(text, mode) {
      * Checks if a given documentRow is folded. This is true if there are some
      * folded parts such that some parts of the line is still visible.
      **/
-    this.isRowFolded = function(docRow) {
-        return !!this.$foldData[docRow];
+    this.isRowFolded = function(docRow, startFoldRow) {
+        return !!this.getFoldRow(docRow, startFoldRow);
     };
 
-    this.getRowLastFold = function(docRow) {
-        var fold = this.$foldData[docRow];
-        if (!fold) {
-            return null;
-        } else if (Array.isArray(fold)) {
-            return fold[fold.length - 1];
-        } else {
-            return fold;
-        }
-    };
-
-    this.getRowFirstFold = function(docRow, skipLastWrap) {
-        var fold = this.$foldData[docRow];
-        if (!fold) {
-            return null;
-        } else if (Array.isArray(fold)) {
-            if (skipLastWrap) {
-                if (fold[0].row.start != docRow) {
-                    return fold[1] || null;
-                }
-            }
-            return fold[0];
-        } else {
-            return fold;
-        }
-    };
-
-    this.getRowFoldEnd = function(docRow) {
-        return (this.$foldData[docRow]
-                    ? this.getRowLastFold(docRow).end.row
+    this.getRowFoldEnd = function(docRow, startFoldRow) {
+        var foldRow = this.getFoldRow(docRow, startFoldRow);
+        return (foldRow
+                    ? (foldRow.linkOut ? foldRow.linkOut.end.row : docRow)
                     : docRow);
     };
 
-    /**
-     * Checks if a given documentRow is visible or not. Not beeing visible means
-     * it's folded completly.
-     **/
-    this.isRowVisible = function(docRow) {
-        var fold = this.$foldData[docRow];
-        return !fold || Array.isArray(fold);
-    };
+    this.buildFoldRowLine = function(docRow, startFoldRow) {
+        var foldRow = this.getFoldRow(docRow, startFoldRow);
+        var folds = [];
+        if (!foldRow) {
+            throw "Passed in docRow doesn't have a foldRow";
+        }
+        if (foldRow.linkIn) {
+            throw "Can't build a single fold line starting at a FoldRow that is linked in!";
+        }
 
-    this.getFoldData = function(docRow) {
-        return this.$foldData[docRow];
+        var foldData = this.$foldData;
+        for (var i = foldData.indexOf(foldRow); foldRow; i++) {
+            if (foldRow.linkIn) {
+                folds.push(foldRow.linkIn);
+            }
+
+            foldRow = foldRow.linkOut;
+        }
     }
 
-    /**
-     * Returns the number of folded lines between start and end row.
-     */
-    this.getFoldedRowLength = function(start, end) {
-        var row = start;
-        var count = 0;
-        while (row <= end) {
-            row = this.findRowFoldedForward(row, end);
-            if (row != null) {
-                var fold = this.getRowLastFold(row);
-                if (!fold.sameLine) {
-                    if (row == start) {
-                        count += fold.end.row - start;
-                    } else {
-                        count += fold.end.row - fold.start.row;
-                    }
-                    row = fold.end.row + 1;
-                }
-            } else {
-                break;
-            }
-        }
-        return count;
-    };
-
-    this.findRowFoldedForward = function(start, limit) {
-        if (limit == null) {
-            limit = this.getLength();
-        }
-        for (var row = start; row != limit; row++) {
-            if (this.isRowFolded(row)) {
-                return row;
-            }
-        }
-        return null;
-    }
-
-    this.findRowFoldedBackwards = function(start, limit) {
-        if (limit == null) {
-            limit = -1;
-        }
-        for (var row = start; row != limit; row--) {
-            if (this.isRowFolded(row)) {
-                return row;
-            }
-        }
-        return null;
-    }
+//    this.findRowFoldedForward = function(start, limit) {
+//        if (limit == null) {
+//            limit = this.getLength();
+//        }
+//        for (var row = start; row != limit; row++) {
+//            if (this.isRowFolded(row)) {
+//                return row;
+//            }
+//        }
+//        return null;
+//    }
+//
+//    this.findRowFoldedBackwards = function(start, limit) {
+//        if (limit == null) {
+//            limit = -1;
+//        }
+//        for (var row = start; row != limit; row--) {
+//            if (this.isRowFolded(row)) {
+//                return row;
+//            }
+//        }
+//        return null;
+//    }
 
 }).call(EditSession.prototype);
 
diff --git a/lib/ace/edit_session_test.js b/lib/ace/edit_session_test.js
index 948802a3..d9d6caf9 100644
--- a/lib/ace/edit_session_test.js
+++ b/lib/ace/edit_session_test.js
@@ -20,6 +20,7 @@
  *
  * Contributor(s):
  *      Fabian Jakobs <fabian AT ajax DOT org>
+ *      Julian Viereck <julian DOT viereck AT gmail DOT com>
  *
  * Alternatively, the contents of this file may be used under the terms of
  * either the GNU General Public License Version 2 or later (the "GPL"), or
@@ -49,6 +50,21 @@ var MockRenderer = require("ace/test/mockrenderer");
 var Range = require("ace/range").Range;
 var assert = require("ace/test/assertions");
 
+function createFoldTestSession() {
+    var lines = [
+        "function foo(items) {",
+        "    for (var i=0; i<items.length; i++) {",
+        "        alert(items[i] + \"juhu\");",
+        "    }    // Real Tab.",
+        "}"
+    ];
+    var session = new EditSession(lines.join("\n"));
+    session.addFold(new Range(0, 13, 0, 18), "args...");
+    session.addFold(new Range(1, 10, 2, 10), "foo...");
+    session.addFold(new Range(2, 20, 2, 25), "bar...");
+    return session;
+}
+
 module.exports = {
 
    "test: find matching opening bracket" : function() {
@@ -353,6 +369,44 @@ module.exports = {
         session.setValue("\nfoo");
 
         assert.equal(session.doc.getValue(), ["", "foo"].join("\n"));
+    },
+
+    "test fold documentToScreen": function() {
+        var session = createFoldTestSession();
+        function assertDoc2Screen(docRow, docCol, screenRow, screenCol) {
+            assert.position(
+                session.documentToScreenPosition(docRow, docCol),
+                screenRow, screenCol
+            );
+        }
+
+        // One fold ending in the same row.
+        assertDoc2Screen(0,  0, 0, 0);
+        assertDoc2Screen(0, 13, 0, 13);
+        assertDoc2Screen(0, 14, 0, 13);
+        assertDoc2Screen(0, 17, 0, 13);
+        assertDoc2Screen(0, 18, 0, 20);
+
+        // Fold ending on some other row.
+        assertDoc2Screen(1,  0, 1, 0);
+        assertDoc2Screen(1, 10, 1, 10);
+        assertDoc2Screen(1, 11, 1, 10);
+        assertDoc2Screen(1, 99, 1, 10);
+
+        assertDoc2Screen(2,  0, 1, 10);
+        assertDoc2Screen(2,  9, 1, 10);
+        assertDoc2Screen(2, 10, 1, 16);
+        assertDoc2Screen(2, 11, 1, 17);
+
+        // Fold in the same row with fold over more then one row in the same row.
+        assertDoc2Screen(2, 19, 1, 25);
+        assertDoc2Screen(2, 20, 1, 26);
+        assertDoc2Screen(2, 21, 1, 26);
+
+        assertDoc2Screen(2, 24, 1, 26);
+        assertDoc2Screen(2, 25, 1, 32);
+        assertDoc2Screen(2, 26, 1, 33);
+        assertDoc2Screen(2, 99, 1, 40);
     }
 };
 
diff --git a/lib/ace/test/all_browser.js b/lib/ace/test/all_browser.js
index 7ec7e3f2..99e4267f 100644
--- a/lib/ace/test/all_browser.js
+++ b/lib/ace/test/all_browser.js
@@ -10,27 +10,27 @@ var failed = 0
 var log = document.getElementById("log")
 
 var tests = [
-    require("ace/editor_change_document_test"),
-    require("ace/editor_navigation_test"),
-    require("ace/editor_highlight_selected_word_test"),
-    require("ace/editor_text_edit_test"),
-    require("ace/document_test"),
-    require("ace/edit_session_test"),
-    require("ace/test/event_emitter_test"),
-    require("ace/range_test"),
-    require("ace/search_test"),
-    require("ace/selection_test"),
-    require("ace/virtual_renderer_test"),
-    require("ace/anchor_test"),
-    require("ace/mode/css_test"),
-    require("ace/mode/css_tokenizer_test"),
-    require("ace/mode/html_test"),
-    require("ace/mode/html_tokenizer_test"),
-    require("ace/mode/javascript_test"),
-    require("ace/mode/javascript_tokenizer_test"),
-    require("ace/mode/text_test"),
-    require("ace/mode/xml_test"),
-    require("ace/mode/xml_tokenizer_test")
+    // require("ace/editor_change_document_test"),
+    // require("ace/editor_navigation_test"),
+    // require("ace/editor_highlight_selected_word_test"),
+    // require("ace/editor_text_edit_test"),
+    // require("ace/document_test"),
+    require("ace/edit_session_test") //,
+    // require("ace/test/event_emitter_test"),
+    // require("ace/range_test"),
+    // require("ace/search_test"),
+    // require("ace/selection_test"),
+    // require("ace/virtual_renderer_test"),
+    // require("ace/anchor_test"),
+    // require("ace/mode/css_test"),
+    // require("ace/mode/css_tokenizer_test"),
+    // require("ace/mode/html_test"),
+    // require("ace/mode/html_tokenizer_test"),
+    // require("ace/mode/javascript_test"),
+    // require("ace/mode/javascript_tokenizer_test"),
+    // require("ace/mode/text_test"),
+    // require("ace/mode/xml_test"),
+    // require("ace/mode/xml_tokenizer_test")
 ]
 
 async.list(tests)
@@ -41,21 +41,21 @@ async.list(tests)
     .each(function(test, next) {
         var node = document.createElement("div");
         node.className = test.passed ? "passed" : "failed";
-        
+
         var name = test.name
         if (test.suiteName)
             name = test.suiteName + ": " + test.name
-            
+
         var msg = "[" + test.count + "/" + test.index + "] " + name + " " + (test.passed ? "OK" : "FAIL")
         if (!test.passed) {
             if (test.err.stack)
                 var err = test.err.stack
             else
                 var err = test.err
-            
+
             msg += "<pre class='error'>" + err + "</pre>";
         }
-        
+
         node.innerHTML = msg;
         log.appendChild(node);