backspace should eat 4 spaces when the cursor is positioned after a tab

(also for navigation and selection)

lib/ace/document.js

@@ -161,6 +161,10 @@ var Document = function(text, mode) {
         return this.$tabSize;
     };
     
+    this.isTabStop = function(position) {
+        return this.$useSoftTabs && (position.column % this.$tabSize == 0);
+    };
+
     this.getBreakpoints = function() {
         return this.$breakpoints;
     };

lib/ace/editor.js

@@ -590,9 +590,9 @@ var Editor =function(renderer, doc) {
         if (this.$readOnly)
             return;
 
-        if (this.selection.isEmpty()) {
+        if (this.selection.isEmpty())
             this.selection.selectLeft();
-        }
+        
         this.moveCursorToPosition(this.doc.remove(this.getSelectionRange()));
         this.clearSelection();
     };

lib/ace/selection.js

@@ -265,13 +265,20 @@ var Selection = function(doc) {
 
     this.moveCursorLeft = function() {
         if (this.selectionLead.column == 0) {
+            // cursor is a line start
             if (this.selectionLead.row > 0) {
                 this.moveCursorTo(this.selectionLead.row - 1, this.doc
                         .getLine(this.selectionLead.row - 1).length);
             }
         }
         else {
-            this.moveCursorBy(0, -1);
+            var doc = this.doc;
+            var tabSize = doc.getTabSize();
+            var cursor = this.selectionLead;
+            if (doc.isTabStop(cursor) && doc.getLine(cursor.row).slice(cursor.column-tabSize, cursor.column).split(" ").length-1 == tabSize)
+                this.moveCursorBy(0, -tabSize);
+            else
+                this.moveCursorBy(0, -1);
         }
     };
 
@@ -282,7 +289,13 @@ var Selection = function(doc) {
             }
         }
         else {
-            this.moveCursorBy(0, 1);
+            var doc = this.doc;
+            var tabSize = doc.getTabSize();
+            var cursor = this.selectionLead;
+            if (doc.isTabStop(cursor) && doc.getLine(cursor.row).slice(cursor.column, cursor.column+tabSize).split(" ").length-1 == tabSize)
+                this.moveCursorBy(0, tabSize);
+            else
+                this.moveCursorBy(0, 1);
         }
     };
 

lib/ace/test/text_edit_test.js

@@ -408,7 +408,37 @@ var Test = {
         undoManager.undo();
         doc.$informUndoManager.call();
         assert.equal(doc.toString(), initialText);
-    }
+    },
+    
+    "test: remove left should remove character left of the cursor" : function() {
+        var doc = new Document(["123", "456"]);
+        
+        var editor = new Editor(new MockRenderer(), doc);
+        editor.moveCursorTo(1, 1);
+        editor.removeLeft();
+        assert.equal(doc.toString(), "123\n56");
+    },
+    
+    "test: remove left should remove line break if cursor is at line start" : function() {
+        var doc = new Document(["123", "456"]);
+        
+        var editor = new Editor(new MockRenderer(), doc);
+        editor.moveCursorTo(1, 0);
+        editor.removeLeft();
+        assert.equal(doc.toString(), "123456");
+    },
+    
+    "test: remove left should remove tabsize spaces if cursor is on a tab stop and preceeded by spaces" : function() {
+        var doc = new Document(["123", "        456"]);
+        doc.setUseSoftTabs(true);
+        doc.setTabSize(4);
+    
+        var editor = new Editor(new MockRenderer(), doc);
+        editor.moveCursorTo(1, 8);
+        editor.removeLeft();
+        assert.equal(doc.toString(), "123\n    456");
+    },
+
 };
 
 module.exports = require("async/test").testcase(Test);