Merge branch 'fix-angle-normalization' into 'master'

gsk: Fix angle normalization

See merge request GNOME/gtk!1409

gsk/gsktransform.c

@@ -821,20 +821,28 @@ static const GskTransformClass GSK_ROTATE_TRANSFORM_CLASS =
 static inline float
 normalize_angle (float angle)
 {
-  float f;
 
   if (angle >= 0 && angle < 360)
     return angle;
 
-  f = angle - (360 * ((int)(angle / 360.0)));
+  while (angle >= 360)
+    angle -= 360;
+  while (angle < 0)
+    angle += 360;
 
-  if (f < 0)
-    f = 360 + f;
+  /* Due to precision issues we may end up with a result that is just
+   * past the allowed range when rounded. For example, something like
+   * -epsilon + 360 when rounded to a float may end up with 360.
+   * So, we handle these cases by returning the exact value 0.
+   */
 
-  g_assert (f < 360.0);
-  g_assert (f >= 0.0);
+  if (angle >= 360)
+    angle = 0;
 
-  return f;
+  g_assert (angle < 360.0);
+  g_assert (angle >= 0.0);
+
+  return angle;
 }
 
 /**