cairoSetMiterLimit(cr, limit)CAIRO_LINE_JOIN_MITER
(see cairoSetLineJoin), the miter limit is used to determine
whether the lines should be joined with a bevel instead of a miter.
Cairo divides the length of the miter by the line width.
If the result is greater than the miter limit, the style is
converted to a bevel.
As with the other stroke parameters, the current line miter limit is
examined by cairoStroke, cairoStrokeExtents, and
cairoStrokeToPath(), but does not have any effect during path
construction.