                     marker.clear()
 
     hide_output: (line) =>
-        mark = @find_output_mark(line)
-        if mark?
-            @elt_at_mark(mark).addClass('sagews-output-hide')
+        for cm in [@codemirror, @codemirror1]
+            mark = @find_output_mark(line, cm)
+            if mark?
+                @elt_at_mark(mark).addClass('sagews-output-hide')
 
     show_output: (line) =>
-        mark = @find_output_mark(line)
-        if mark?
-            @elt_at_mark(mark).removeClass('sagews-output-hide')
+        for cm in [@codemirror, @codemirror1]
+            mark = @find_output_mark(line, cm)
+            if mark?
+                @elt_at_mark(mark).removeClass('sagews-output-hide')
 
     execute_code: (opts) ->
         opts = defaults opts,


        return mark

    find_output_line: (line) =>
        # Given a line number in the editor, return the nearest (greater or equal) line number that
        # is an output line, or undefined if there is no output line before the next cell.
        cm = @focused_codemirror()
        if cm.getLine(line)[0] == MARKERS.output
            return line
        line += 1

            line += 1
        return undefined

    find_output_mark: (line, cm) =>
        # Same as find_output_line, but returns the actual mark (or undefined).
        if not cm?
            cm = @focused_codemirror()
        n = @find_output_line(line, cm)
        if n?
            for mark in cm.findMarksAt({line:n, ch:0})
                if mark.type == MARKERS.output
                    return mark
        return undefined
