def add_marker(self, marker):
        """
        Adds the marker to the panel.

        :param marker: Marker to add
        :type marker: pyqode.core.modes.Marker
        """
        self._markers.append(marker)
        doc = self.editor.document()
        assert isinstance(doc, QtGui.QTextDocument)
        block = doc.findBlockByLineNumber(marker._position)
        marker.block = block
        d = TextDecoration(block)
        d.set_full_width()
        if self._background:
            d.set_background(QtGui.QBrush(self._background))
            marker.decoration = d
        self.editor.decorations.append(d)
        self.repaint()