def render_behind fragment
pdf = fragment.document
data = fragment.format_state
prev_fill_color = pdf.fill_color
pdf.fill_color data[:background_color]
if data[:inline_block]
fragment_width = data[:extend] ? pdf.bounds.width - fragment.left : fragment.width
v_gap = @line_gap
else
fragment_width = fragment.width
v_gap = 0
end
pdf.fill_rectangle [fragment.left, fragment.top + v_gap * 0.5], fragment_width, (fragment.height + v_gap)
pdf.fill_color prev_fill_color
fragment.conceal true if fragment.text == DummyText
nil
end