Backport PR #12795: Fix Bezier degree elevation formula in backend_cairo.

jklymak · MeeseeksDev[bot] · commit 0a1071674cd5 · 2018-11-19T17:35:33.000Z
diff --git a/lib/matplotlib/backends/backend_cairo.py b/lib/matplotlib/backends/backend_cairo.py
@@ -99,10 +99,10 @@ def _append_paths_slow(ctx, paths, transforms, clip=None):
             elif code == Path.LINETO:
                 ctx.line_to(*points)
             elif code == Path.CURVE3:
-                cur = ctx.get_current_point()
-                ctx.curve_to(
-                    *np.concatenate([cur / 3 + points[:2] * 2 / 3,
-                                     points[:2] * 2 / 3 + points[-2:] / 3]))
+                cur = np.asarray(ctx.get_current_point())
+                a = points[:2]
+                b = points[-2:]
+                ctx.curve_to(*(cur / 3 + a * 2 / 3), *(a * 2 / 3 + b / 3), *b)
             elif code == Path.CURVE4:
                 ctx.curve_to(*points)
 
