[cairo] [cairo-commit] 3 commits - src/cairo.c src/cairo-path-stroke.c test/get-path-extents.c test/.gitignore test/Makefile.am test/rectilinear-miter-limit.c test/rectilinear-miter-limit-ref.png

[Behdad Esfahbod]

On Mon, 2008-01-21 at 19:47 -0500, Carl Worth wrote:
> 
> +    /* If the miter limit turns right angles into bevels, then we
> +     * can't usethis optimization. Remember, the ratio is
> +     * 1/sin(ɸ/2). So the cutoff is 1/sin(π/4.0) or ⎷2 or
> +     * approximately 1.414213562373095, which we round for safety. */
> +    if (stroke_style->miter_limit < 1.415)
> +       return CAIRO_INT_STATUS_UNSUPPORTED;

I thought about this on the way back home and though, well, what if the
user exactly sets miter to sqrt(2)?  What I mean is, sqrt(2) is one of
the "magic" numbers to use for miter limit as it does a miter up to
right angles, and bevel after.  Then I checked math.h and there indeed
is M_SQRT2 defined.  So I suggest:

  - Somewhere in a portability header:

#ifndef M_SQRT2
#define M_SQRT2 1.414213562373095
#endif

  - Change the check to:

    if (stroke_style->miter_limit < M_SQRT2)
       return CAIRO_INT_STATUS_UNSUPPORTED;

This way if the user sets miter limit exactly to M_SQRT2, we're on the
safe side.

I can push.

-- 
behdad
http://behdad.org/

"Those who would give up Essential Liberty to purchase a little
 Temporary Safety, deserve neither Liberty nor Safety."
        -- Benjamin Franklin, 1759