[sublime] Implement smart backspace with multi-cursor support

keymap/sublime.js

@@ -420,6 +420,34 @@
 
   map[cK + ctrl + "Backspace"] = "delLineLeft";
 
+  cmds[map["Backspace"] = "smartBackspace"] = function(cm) {
+    if (cm.somethingSelected()) return CodeMirror.Pass;
+
+    cm.operation(function() {
+      var cursors = cm.listSelections();
+      var indentUnit = cm.getOption("indentUnit");
+
+      for (var i = cursors.length - 1; i >= 0; i--) {
+        var cursor = cursors[i].head;
+        var toStartOfLine = cm.getRange({line: cursor.line, ch: 0}, cursor);
+        var column = CodeMirror.countColumn(toStartOfLine, null, cm.getOption("tabSize"));
+
+        // Delete by one character by default
+        var deletePos = cm.findPosH(cursor, -1, "char", false);
+
+        if (toStartOfLine && !/\S/.test(toStartOfLine) && column % indentUnit == 0) {
+          var prevIndent = new Pos(cursor.line,
+            CodeMirror.findColumn(toStartOfLine, column - indentUnit, indentUnit));
+
+          // Smart delete only if we found a valid prevIndent location
+          if (prevIndent.ch != cursor.ch) deletePos = prevIndent;
+        }
+
+        cm.replaceRange("", deletePos, cursor, "+delete");
+      }
+    });
+  };
+
   cmds[map[cK + ctrl + "K"] = "delLineRight"] = function(cm) {
     cm.operation(function() {
       var ranges = cm.listSelections();