CairoLineJoin for details about how the available line join
styles are drawn.cairoSetLineJoin(cr, line.join)Cairo] a cairo contextCairoLineJoin] a line join stylecairoStroke, cairoStrokeExtents, and
cairoStrokeToPath(), but does not have any effect during path
construction.
The default line join style is CAIRO_LINE_JOIN_MITER.