'Add fold decorations (boxes arround a folded block in the editor
widget).'

def _add_fold_decoration(self, block, region):

    deco = TextDecoration(block)
    deco.signals.clicked.connect(self._on_fold_deco_clicked)
    deco.tooltip = region.text(max_lines=25)
    deco.draw_order = 1
    deco.block = block
    deco.select_line()
    deco.set_outline(drift_color(self._get_scope_highlight_color(), 110))
    deco.set_background(self._get_scope_highlight_color())
    deco.set_foreground(QColor('#808080'))
    self._block_decos.append(deco)
    self.editor.decorations.append(deco)
