[foldgutter] reuse old markers if indicatorOpen/Folded is string

Author: tophf

addon/fold/foldgutter.js

@@ -71,24 +71,36 @@
   }
 
   function updateFoldInfo(cm, from, to) {
-    var opts = cm.state.foldGutter.options, cur = from;
+    var opts = cm.state.foldGutter.options, cur = from - 1;
     var minSize = cm.foldOption(opts, "minFoldSize");
     var func = cm.foldOption(opts, "rangeFinder");
+    // we can reuse the built-in indicator element if its className matches the new state
+    var clsFolded = typeof opts.indicatorFolded == "string" && classTest(opts.indicatorFolded);
+    var clsOpen = typeof opts.indicatorOpen == "string" && classTest(opts.indicatorOpen);
     cm.eachLine(from, to, function(line) {
+      ++cur;
       var mark = null;
+      var old = line.gutterMarkers;
+      if (old) old = old[opts.gutter];
       if (isFolded(cm, cur)) {
+        if (clsFolded && old && clsFolded.test(old.className)) return;
         mark = marker(opts.indicatorFolded);
       } else {
         var pos = Pos(cur, 0);
         var range = func && func(cm, pos);
-        if (range && range.to.line - range.from.line >= minSize)
+        if (range && range.to.line - range.from.line >= minSize) {
+          if (clsOpen && old && clsOpen.test(old.className)) return;
           mark = marker(opts.indicatorOpen);
+        }
       }
+      if (!mark && !old) return;
       cm.setGutterMarker(line, opts.gutter, mark);
-      ++cur;
     });
   }
 
+  // copied from CodeMirror/src/util/dom.js
+  function classTest(cls) { return new RegExp("(^|\\s)" + cls + "(?:$|\\s)\\s*") }
+
   function updateInViewport(cm) {
     var vp = cm.getViewport(), state = cm.state.foldGutter;
     if (!state) return;