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Eliminate a potential infinite loop in spline stroking

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Sometimes > rather than >= can make a bug difference. The infinite loop
was noticed here:

	Infinite loop when scaling very small values using 24.8
	http://bugs.freedesktop.org/show_bug.cgi?id=14280

Note that that particular test case only exposes the infinite
loop when using 24.8 instead of 16.16 fixed-point values by
setting CAIRO_FIXED_FRAC_BITS to 8.
This commit is contained in:
Carl Worth 2008-02-16 13:27:02 -08:00
parent 770b058c9e
commit d6d81c92b5
1 changed files with 12 additions and 1 deletions
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13
src/cairo-pen.c
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@ -417,7 +417,18 @@ _cairo_pen_stroke_spline_half (cairo_pen_t *pen,
slope = final_slope;
else
_cairo_slope_init (&slope, &point[i], &point[i+step]);
if (_cairo_slope_compare (&slope, &pen->vertices[active].slope_ccw) >= 0) {
/* The strict inequalities here ensure that if a spline slope
* compares identically with either of the slopes of the
* active vertex, then it remains the active vertex. This is
* very important since otherwise we can trigger an infinite
* loop in the case of a degenerate pen, (a line), where
* neither vertex considers itself active for the slope---one
* will consider it as equal and reject, and the other will
* consider it unequal and reject. This is due to the inherent
* ambiguity when comparing slopes that differ by exactly
* pi. */
if (_cairo_slope_compare (&slope, &pen->vertices[active].slope_ccw) > 0) {
if (++active == pen->num_vertices)
active = 0;
} else if (_cairo_slope_compare (&slope, &pen->vertices[active].slope_cw) < 0) {