add FadeFoldWidgets setting

lib/ace/css/editor.css

@@ -289,3 +289,20 @@
     background-color: #FFB4B4;
     border-color: #DE5555;
 }
+
+.ace_fade-fold-widgets .ace_fold-widget {
+    -moz-transition: 0.5s opacity;
+    -webkit-transition: 0.5s opacity;
+    -o-transition: 0.5s opacity;
+    -ms-transition: 0.5s opacity;
+    transition: 0.5s opacity;
+    opacity: 0;
+}
+.ace_fade-fold-widgets:hover .ace_fold-widget {
+    -moz-transition-duration: 0s;
+    -webkit-transition-duration: 0s;
+    -o-transition-duration: 0s;
+    -ms-transition-duration: 0s;
+    transition-duration: 0s;
+    opacity:1;
+}

lib/ace/editor.js

@@ -666,6 +666,14 @@ var Editor = function(renderer, session, listenElement) {
         return this.renderer.$gutterLayer.getShowFoldWidgets();
     };
 
+    this.setFadeFoldWidgets = function(show) {
+        this.renderer.setFadeFoldWidgets(show);
+    };
+
+    this.getFadeFoldWidgets = function() {
+        return this.renderer.getFadeFoldWidgets();
+    };
+
     this.remove = function(dir) {
         if (this.selection.isEmpty()){
             if(dir == "left")

lib/ace/virtual_renderer.js

@@ -332,6 +332,17 @@ var VirtualRenderer = function(container, theme) {
         this.onResize(true);
     };
 
+    this.getFadeFoldWidgets = function(){
+        return dom.hasCssClass(this.$gutter, "ace_fade-fold-widgets");
+    };
+
+    this.setFadeFoldWidgets = function(show) {
+        if (show)
+            dom.addCssClass(this.$gutter, "ace_fade-fold-widgets");
+        else
+            dom.removeCssClass(this.$gutter, "ace_fade-fold-widgets");
+    };
+
     this.$updatePrintMargin = function() {
         var containerEl;