For add new selection, use display column

src/editor/Editor.js

@@ -905,6 +905,34 @@ define(function (require, exports, module) {
         return column;
     };
 
+    /**
+     * Returns the string-based pos for a given display column (zero-based) in given line. Differs from column
+     * only when the line contains preceding \t chars. Result depends on the current tab size setting.
+     * @param {number} lineNum Line number
+     * @param {number} column Display column number
+     * @return {number}
+     */
+    Editor.prototype.getCharIndexForColumn = function (lineNum, column) {
+        var line    = this._codeMirror.getLine(lineNum),
+            tabSize = null,
+            iCol    = 0,
+            i;
+
+        for (i = 0; iCol < column; i++) {
+            if (line[i] === '\t') {
+                if (tabSize === null) {
+                    tabSize = Editor.getTabSize();
+                }
+                if (tabSize > 0) {
+                    iCol += (tabSize - (iCol % tabSize));
+                }
+            } else {
+                iCol++;
+            }
+        }
+        return i;
+    };
+
     /**
      * Sets the cursor position within the editor. Removes any selection.
      * @param {number} line  The 0 based line number.

src/editor/EditorCommandHandlers.js

@@ -979,14 +979,22 @@ define(function (require, exports, module) {
             var origSels = editor.getSelections(),
                 newSels = [];
             _.each(origSels, function (sel) {
-                var pos;
+                var pos, colOffset;
                 if ((dir === -1 && sel.start.line > editor.getFirstVisibleLine()) || (dir === 1 && sel.end.line < editor.getLastVisibleLine())) {
                     // Add a new cursor on the next line up/down. It's okay if it overlaps another selection, because CM
                     // will take care of throwing it away in that case. It will also take care of clipping the char position
                     // to the end of the new line if the line is shorter.
                     pos = _.clone(dir === -1 ? sel.start : sel.end);
+
+                    // get sel column of current selection
+                    colOffset = editor.getColOffset(pos);
+
                     pos.line += dir;
 
+                    // translate column to ch in line of new selection
+                    pos.ch = editor.getCharIndexForColumn(pos.line, colOffset);
+
+
                     // If this is the primary selection, we want the new cursor we're adding to become the
                     // primary selection.
                     newSels.push({start: pos, end: pos, primary: sel.primary});

test/spec/EditorCommandHandlers-test.js

@@ -47,6 +47,11 @@ define(function (require, exports, module) {
                              "\n" +
                              "}";
 
+        var tabbedContent =    "function funcWithTabs() {\n" +
+                               "	var i		= 0;\n" +
+                               "	var	offset	= 0;\n" +
+                               "}";
+
         var myDocument, myEditor;
 
         var testPath = SpecRunnerUtils.getTestPath("/spec/EditorCommandHandlers-test-files"),
@@ -3316,6 +3321,26 @@ define(function (require, exports, module) {
 
         });
 
+        describe("Add Line to Selection with Tabs", function () {
+            beforeEach(function () {
+                setupFullEditor(tabbedContent);
+            });
+
+            it("should add a cursor on the next line before a single cursor in same visual position", function () {
+                myEditor.setSelection({line: 1, ch: 8}, {line: 1, ch: 8});
+                CommandManager.execute(Commands.EDIT_ADD_NEXT_LINE_TO_SEL, myEditor);
+                expectSelections([{start: {line: 1, ch:  8}, end: {line: 1, ch:  8}, primary: false, reversed: false},
+                                  {start: {line: 2, ch: 12}, end: {line: 2, ch: 12}, primary: true,  reversed: false}]);
+            });
+
+            it("should add a cursor on the previous line before a single cursor selection in same visual position", function () {
+                myEditor.setSelection({line: 2, ch: 12}, {line: 2, ch: 12});
+                CommandManager.execute(Commands.EDIT_ADD_PREV_LINE_TO_SEL, myEditor);
+                expectSelections([{start: {line: 1, ch:  8}, end: {line: 1, ch:  8}, primary: true,  reversed: false},
+                                  {start: {line: 2, ch: 12}, end: {line: 2, ch: 12}, primary: false, reversed: false}]);
+            });
+        });
+
         describe("EditorCommandHandlers Integration", function () {
             this.category = "integration";