- selection can be extended by shift clicking

- clicking on the start of a selection clears it

src/ace/Editor.js

@@ -271,9 +271,13 @@ var Editor = function(renderer, doc) {
         var pos = this.renderer.screenToTextCoordinates(pageX, pageY);
         pos.row = Math.max(0, Math.min(pos.row, this.doc.getLength()-1));
 
-        this.moveCursorToPosition(pos);
-        if (!this.$clickSelection)
-            this.selection.setSelectionAnchor(pos.row, pos.column);
+        if (e.shiftKey)
+            this.selection.selectToPosition(pos)
+        else {
+            this.moveCursorToPosition(pos);
+            if (!this.$clickSelection)
+                this.selection.clearSelection(pos.row, pos.column);
+        }
 
         this.renderer.scrollCursorIntoView();
 

src/ace/Selection.js

@@ -363,6 +363,7 @@ var Selection = function(doc) {
     this.moveCursorTo = function(row, column) {
         var cursor = this.$clipPositionToDocument(row, column);
 
+        // only dispatch change if the cursor actually changed
         if (cursor.row !== this.selectionLead.row || cursor.column !== this.selectionLead.column) {
             this.selectionLead = cursor;
             this.$dispatchEvent("changeCursor", { data: this.getCursor() });