text: // Utility function that allows modes to be combined. The mode given
  // as the base argument takes care of most of the normal mode
  // functionality, but a second (typically simple) mode is used, which
  // can override the style of text. Both modes get to parse all of the
  // text, but when both assign a non-null style to a piece of code, the
  // overlay wins, unless the combine argument was true, in which case
  // the styles are combined.
  
  CodeMirror.overlayParser = function (base, overlay, combine) {
      return {
          startState: function () {
              return {
                  base: CodeMirror.startState(base),
                  overlay: CodeMirror.startState(overlay),
                  basePos: 0, baseCur: null,
                  overlayPos: 0, overlayCur: null
              };
          },
          copyState: function (state) {
              return {
                  base: CodeMirror.copyState(base, state.base),
                  overlay: CodeMirror.copyState(overlay, state.overlay),
                  basePos: state.basePos, baseCur: null,
                  overlayPos: state.overlayPos, overlayCur: null
              };
          },
  
          token: function (stream, state) {
              if (stream.start == state.basePos) {
                  state.baseCur = base.token(stream, state.base);
                  state.basePos = stream.pos;
              }
              if (stream.start == state.overlayPos) {
                  stream.pos = stream.start;
                  state.overlayCur = overlay.token(stream, state.overlay);
                  state.overlayPos = stream.pos;
              }
              stream.pos = Math.min(state.basePos, state.overlayPos);
              if (stream.eol()) state.basePos = state.overlayPos = 0;
  
              if (state.overlayCur == null) return state.baseCur;
              if (state.baseCur != null && combine) return state.baseCur + " " + state.overlayCur;
              else return state.overlayCur;
          },
  
          indent: function (state, textAfter) {
              return base.indent(state.base, textAfter);
          },
          electricChars: base.electricChars
      };
  };
  