Replace inverse transform with Cross-product computation.

cc/quads/draw_polygon_unittest.cc

Index: cc/quads/draw_polygon_unittest.cc
diff --git a/cc/quads/draw_polygon_unittest.cc b/cc/quads/draw_polygon_unittest.cc
index 0fc25e340721c1c15b7096405e895800096fb116..4dc2883ba4548bd37273cfe961407a7c4fedab27 100644
--- a/cc/quads/draw_polygon_unittest.cc
+++ b/cc/quads/draw_polygon_unittest.cc
@@ -11,11 +11,20 @@
 #include "ui/gfx/transform.h"
 
 namespace cc {
+
+void DrawPolygon::RecomputeNormalForTesting() {
+  ConstructNormal();
+}
+
 namespace {
 
 #define CREATE_NEW_DRAW_POLYGON(name, points_vector, normal, polygon_id) \
   DrawPolygon name(NULL, points_vector, normal, polygon_id)
 
+#define CREATE_TEST_DRAW_POLYGON(name, points_vector, polygon_id)             \
+  DrawPolygon name(NULL, points_vector, gfx::Vector3dF(1, 2, 3), polygon_id); \
+  name.RecomputeNormalForTesting()
+
 #define EXPECT_FLOAT_WITHIN_EPSILON_OF(a, b) \
   EXPECT_TRUE(std::abs(a - b) < std::numeric_limits<float>::epsilon());
 
@@ -24,6 +33,11 @@ namespace {
   EXPECT_FLOAT_EQ(point_a.y(), point_b.y()); \
   EXPECT_FLOAT_EQ(point_a.z(), point_b.z());
 
+#define EXPECT_NORMAL(poly, n_x, n_y, n_z)                \
+  EXPECT_FLOAT_WITHIN_EPSILON_OF(poly.normal().x(), n_x); \
+  EXPECT_FLOAT_WITHIN_EPSILON_OF(poly.normal().y(), n_y); \
+  EXPECT_FLOAT_WITHIN_EPSILON_OF(poly.normal().z(), n_z);
+
 static void ValidatePoints(const DrawPolygon& polygon,
                            const std::vector<gfx::Point3F>& points) {
   EXPECT_EQ(polygon.points().size(), points.size());
@@ -32,6 +46,96 @@ static void ValidatePoints(const DrawPolygon& polygon,
   }
 }
 
+// A simple square in a plane.
+TEST(DrawPolygonConstructionTest, NormalNormal) {
+  std::vector<gfx::Point3F> vertices;
+  vertices.push_back(gfx::Point3F(0.0f, 10.0f, 0.0f));
+  vertices.push_back(gfx::Point3F(0.0f, 0.0f, 0.0f));
+  vertices.push_back(gfx::Point3F(10.0f, 0.0f, 0.0f));
+  vertices.push_back(gfx::Point3F(10.0f, 10.0f, 0.0f));
+
+  gfx::Transform Identity;
+  DrawPolygon polygon(NULL, gfx::RectF(10.0, 10.0), Identity, 1);
+  EXPECT_NORMAL(polygon, 0.0, 0.0, 1.0);
+}
+
+// More complicated shapes.
+TEST(DrawPolygonConstructionTest, TestNormal) {
+  std::vector<gfx::Point3F> vertices;
+  vertices.push_back(gfx::Point3F(0.0f, 10.0f, 0.0f));
+  vertices.push_back(gfx::Point3F(0.0f, 0.0f, 0.0f));
+  vertices.push_back(gfx::Point3F(10.0f, 0.0f, 0.0f));
+  vertices.push_back(gfx::Point3F(10.0f, 10.0f, 0.0f));
+
+  CREATE_TEST_DRAW_POLYGON(polygon, vertices, 1);
+  EXPECT_NORMAL(polygon, 0.0, 0.0, 1.0);
+}
+
+TEST(DrawPolygonConstructionTest, ClippedNormal) {
+  std::vector<gfx::Point3F> vertices;
+  vertices.push_back(gfx::Point3F(0.1f, 10.0f, 0.0f));
+  vertices.push_back(gfx::Point3F(0.0f, 9.9f, 0.0f));
+  vertices.push_back(gfx::Point3F(0.0f, 10.0f, 0.0f));
+  vertices.push_back(gfx::Point3F(0.0f, 0.0f, 0.0f));
+  vertices.push_back(gfx::Point3F(10.0f, 0.0f, 0.0f));
+  vertices.push_back(gfx::Point3F(10.0f, 10.0f, 0.0f));
+
+  CREATE_TEST_DRAW_POLYGON(polygon, vertices, 1);
+  EXPECT_NORMAL(polygon, 0.0, 0.0, 1.0);
+}
+
+TEST(DrawPolygonConstructionTest, SlimTriangleNormal) {
+  std::vector<gfx::Point3F> vertices;
+  vertices.push_back(gfx::Point3F(0.0f, 0.0f, 0.0f));
+  vertices.push_back(gfx::Point3F(5000.0f, 0.0f, 0.0f));
+  vertices.push_back(gfx::Point3F(10000.0f, 1.0f, 0.0f));
+
+  CREATE_TEST_DRAW_POLYGON(polygon, vertices, 2);
+  EXPECT_NORMAL(polygon, 0.0, 0.0, 1.0);

[Peter Mayo, 2015/12/04 04:33:56]

Perhaps one that isn't axis-aligned?

[Peter Mayo, 2015/12/04 05:21:34]

Added in the transform test.

+}
+
+TEST(DrawPolygonConstructionTest, ManyVertexNormal) {
+  std::vector<gfx::Point3F> vertices_c;
+  std::vector<gfx::Point3F> vertices_d;
+  for (int i = 0; i < 100; i++) {
+    vertices_c.push_back(
+        gfx::Point3F(cos(i * M_PI / 50), sin(i * M_PI / 50), 0.0f));
+    vertices_d.push_back(gfx::Point3F(cos(i * M_PI / 50) + 99.0,
+                                      sin(i * M_PI / 50) + 99.0, 100.0f));
+  }
+  CREATE_TEST_DRAW_POLYGON(polygon_c, vertices_c, 3);
+  EXPECT_NORMAL(polygon_c, 0.0, 0.0, 1.0);
+
+  CREATE_TEST_DRAW_POLYGON(polygon_d, vertices_d, 4);
+  EXPECT_NORMAL(polygon_c, 0.0, 0.0, 1.0);
+}
+
+// A simple rect being transformed.
+TEST(DrawPolygonConstructionTest, DizzyNormal) {
+  gfx::RectF src(-0.1, -10.0, 0.2, 20.0);
+
+  gfx::Transform transform_i(1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1);
+  DrawPolygon polygon_i(NULL, src, transform_i, 1);
+
+  EXPECT_NORMAL(polygon_i, 0.0, 0.0, 1.0);
+
+  gfx::Transform tranform_a(0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1);
+  DrawPolygon polygon_a(NULL, src, tranform_a, 2);
+  EXPECT_NORMAL(polygon_a, 0.0, 0.0, -1.0);
+
+  gfx::Transform tranform_b(0, 0, 1, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 0, 1);
+  DrawPolygon polygon_b(NULL, src, tranform_b, 3);
+  EXPECT_NORMAL(polygon_b, -1.0, 0.0, 0.0);
+
+  gfx::Transform tranform_c(1, 0, 0, 0, 0, 0, 1, 0, 0, 1, 0, 0, 0, 0, 0, 1);
+  DrawPolygon polygon_c(NULL, src, tranform_c, 4);
+  EXPECT_NORMAL(polygon_c, 0.0, -1.0, 0.0);
+
+  gfx::Transform tranform_d(-1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1, 0, 0, 0, 0, 1);
+  DrawPolygon polygon_d(NULL, src, tranform_d, 5);
+  EXPECT_NORMAL(polygon_d, 0.0, 0.0, -1.0);
+}
+
 // Two quads are nearly touching but definitely ordered. Second one should
 // compare in front.
 TEST(DrawPolygonSplitTest, NearlyTouchingOrder) {
@@ -228,9 +332,7 @@ TEST(DrawPolygonTransformTest, TransformNormal) {
   // because some architectures (e.g., Arm64) employ a fused multiply-add
   // instruction which causes rounding asymmetry and reduces precision.
   // http://crbug.com/401117.
-  EXPECT_FLOAT_WITHIN_EPSILON_OF(polygon_a.normal().x(), 0);
-  EXPECT_FLOAT_WITHIN_EPSILON_OF(polygon_a.normal().y(), 0);
-  EXPECT_FLOAT_WITHIN_EPSILON_OF(polygon_a.normal().z(), -1);
+  EXPECT_NORMAL(polygon_a, 0.0, 0.0, -1.0);
 }
 
 }  // namespace