Fix cursor rendering (#2932)

* Fixes rendering bugs for cursor and marker

core/keyboard_nav/cursor_svg.js

@@ -94,6 +94,18 @@ Blockly.CursorSvg.CURSOR_COLOR = '#cc0a0a';
  */
 Blockly.CursorSvg.MARKER_COLOR = '#4286f4';
 
+/**
+ * The name of the css class for a cursor.
+ * @const {string}
+ */
+Blockly.CursorSvg.CURSOR_CLASS = 'blocklyCursor';
+
+/**
+ * The name of the css class for a marker.
+ * @const {string}
+ */
+Blockly.CursorSvg.MARKER_CLASS = 'blocklyMarker';
+
 /**
  * Parent SVG element.
  * This is generally a block's SVG root, unless the cursor is on the workspace.
@@ -120,7 +132,9 @@ Blockly.CursorSvg.prototype.getSvgRoot = function() {
  * @return {!Element} The cursor controls SVG group.
  */
 Blockly.CursorSvg.prototype.createDom = function() {
-  var className = this.isMarker_ ? 'blocklyMarker' : 'blocklyCursor';
+  var className = this.isMarker_ ?
+      Blockly.CursorSvg.MARKER_CLASS : Blockly.CursorSvg.CURSOR_CLASS;
+
   this.svgGroup_ =
       Blockly.utils.dom.createSvgElement('g', {
         'class': className
@@ -142,9 +156,20 @@ Blockly.CursorSvg.prototype.setParent_ = function(newParent) {
     return;
   }
   var svgRoot = this.getSvgRoot();
+  var cursorNode = null;
 
   if (newParent) {
-    newParent.appendChild(svgRoot);
+    if (this.isMarker_) {
+      // Put the marker before the cursor so the cursor does not get covered.
+      for (var i = 0, childNode; childNode = newParent.childNodes[i]; i++) {
+        if (Blockly.utils.dom.hasClass(childNode , Blockly.CursorSvg.CURSOR_CLASS)) {
+          cursorNode = childNode;
+        }
+      }
+      newParent.insertBefore(svgRoot, cursorNode);
+    } else {
+      newParent.appendChild(svgRoot);
+    }
     this.parent_ = newParent;
   }
 };

core/keyboard_nav/navigation.js

@@ -132,7 +132,6 @@ Blockly.navigation.setMarker = function(marker) {
  * @package
  */
 Blockly.navigation.markAtCursor = function() {
-  // TODO: bring the cursor (blinking) in front of the marker (solid)
   Blockly.navigation.marker_.setLocation(
       Blockly.navigation.cursor_.getCurNode());
 };