Function indentLine

lib/codemirror/lib/codemirror.js:4532–4588

(cm, n, how, aggressive)

  // lines are not indented, and places where the mode returns Pass
  // are left alone.
  function indentLine(cm, n, how, aggressive) {
    var doc = cm.doc, state;
    if (how == null) how = "add";
    if (how == "smart") {
      // Fall back to "prev" when the mode doesn't have an indentation
      // method.
      if (!doc.mode.indent) how = "prev";
      else state = getStateBefore(cm, n);
    }

    var tabSize = cm.options.tabSize;
    var line = getLine(doc, n), curSpace = countColumn(line.text, null, tabSize);
    if (line.stateAfter) line.stateAfter = null;
    var curSpaceString = line.text.match(/^\s*/)[0], indentation;
    if (!aggressive && !/\S/.test(line.text)) {
      indentation = 0;
      how = "not";
    } else if (how == "smart") {
      indentation = doc.mode.indent(state, line.text.slice(curSpaceString.length), line.text);
      if (indentation == Pass || indentation > 150) {
        if (!aggressive) return;
        how = "prev";
      }
    }
    if (how == "prev") {
      if (n > doc.first) indentation = countColumn(getLine(doc, n-1).text, null, tabSize);
      else indentation = 0;
    } else if (how == "add") {
      indentation = curSpace + cm.options.indentUnit;
    } else if (how == "subtract") {
      indentation = curSpace - cm.options.indentUnit;
    } else if (typeof how == "number") {
      indentation = curSpace + how;
    }
    indentation = Math.max(0, indentation);

    var indentString = "", pos = 0;
    if (cm.options.indentWithTabs)
      for (var i = Math.floor(indentation / tabSize); i; --i) {pos += tabSize; indentString += "\t";}
    if (pos < indentation) indentString += spaceStr(indentation - pos);

    if (indentString != curSpaceString) {
      replaceRange(doc, indentString, Pos(n, 0), Pos(n, curSpaceString.length), "+input");
    } else {
      // Ensure that, if the cursor was in the whitespace at the start
      // of the line, it is moved to the end of that space.
      for (var i = 0; i < doc.sel.ranges.length; i++) {
        var range = doc.sel.ranges[i];
        if (range.head.line == n && range.head.ch < curSpaceString.length) {
          var pos = Pos(n, curSpaceString.length);
          replaceOneSelection(doc, i, new Range(pos, pos));
          break;
        }
      }
    }
    line.stateAfter = null;
  }