1 files changed, 51 insertions, 0 deletions

diff --git a/js/codemirror/lib/overlay.js b/js/codemirror/lib/overlay.js
new file mode 100644
index 00000000..c4cdf9fc
--- /dev/null
+++ b/js/codemirror/lib/overlay.js
@@ -0,0 +1,51 @@
+// 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
+  };
+};