[spline] Treat a straight spline as degenerate.

The fallback for degenerate splines is to treat them as a line-to, so if
the spline is straight, we can just replace it with a simple line-to by
treating as degenerate.

1 files changed, 9 insertions, 0 deletions

diff --git a/src/cairo-spline.c b/src/cairo-spline.c
index 45eedbd6a..8bebcb2a8 100644
--- a/src/cairo-spline.c
+++ b/src/cairo-spline.c
@@ -43,6 +43,8 @@ _cairo_spline_init (cairo_spline_t *spline,
 		    const cairo_point_t *a, const cairo_point_t *b,
 		    const cairo_point_t *c, const cairo_point_t *d)
 {
+    cairo_slope_t slope;
+
     spline->add_point_func = add_point_func;
     spline->closure = closure;
 
@@ -67,6 +69,13 @@ _cairo_spline_init (cairo_spline_t *spline,
     else
 	_cairo_slope_init (&spline->final_slope, &spline->knots.a, &spline->knots.d);
 
+    _cairo_slope_init (&slope, &spline->knots.a, &spline->knots.d);
+    if (_cairo_slope_compare (&slope, &spline->initial_slope) == 0 &&
+	_cairo_slope_compare (&slope, &spline->final_slope) == 0)
+    {
+	return FALSE; /* just a straight line... */
+    }
+
     return TRUE;
 }