Bug 1843950: Change BasePoint::Length() return type to avoid truncation to int. r=botond

Created a new metafunction, FloatType, which will prevent truncation of the
decimal portion of the Length method result. Added GTest unit tests, and converted
old unit tests in gfx/2d/unittest/TestPoint.cpp to gtests.

Differential Revision: https://phabricator.services.mozilla.com/D208306

gfx/2d/BasePoint.h

@@ -12,10 +12,37 @@
 #include <type_traits>
 #include "mozilla/Attributes.h"
 #include "mozilla/FloatingPoint.h"
+#include "Coord.h"
 
 namespace mozilla {
 namespace gfx {
 
+template <class T, typename EnableT = void>
+struct FloatType;
+
+template <typename T>
+struct FloatType<T, typename std::enable_if_t<std::is_integral_v<T>>> {
+  using type = float;
+};
+
+template <typename T>
+struct FloatType<T, typename std::enable_if_t<std::is_floating_point_v<T>>> {
+  using type = T;
+};
+
+template <typename Units, typename Rep>
+struct FloatType<IntCoordTyped<Units, Rep>> {
+  using type = CoordTyped<Units, float>;
+};
+
+template <typename Units, typename Rep>
+struct FloatType<CoordTyped<Units, Rep>> {
+  using type = CoordTyped<Units, Rep>;
+};
+
+template <typename T>
+using FloatType_t = typename FloatType<T>::type;
+
 /**
  * Do not use this class directly. Subclass it, pass that subclass as the
  * Sub parameter, and only use that subclass. This allows methods to safely
@@ -82,9 +109,8 @@ struct BasePoint {
     return x.value * aPoint.x.value + y.value * aPoint.y.value;
   }
 
-  // FIXME: Maybe Length() should return a float Coord event for integer Points?
-  Coord Length() const {
-    return static_cast<decltype(x.value)>(hypot(x.value, y.value));
+  FloatType_t<Coord> Length() const {
+    return FloatType_t<Coord>(hypot(x.value, y.value));
   }
 
   T LengthSquare() const { return x.value * x.value + y.value * y.value; }

gfx/2d/unittest/TestPoint.cpp

@@ -1,53 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set ts=8 sts=2 et sw=2 tw=80: */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#include "TestPoint.h"
-
-#include "Point.h"
-
-using namespace mozilla::gfx;
-
-TestPoint::TestPoint() {
-  REGISTER_TEST(TestPoint, Addition);
-  REGISTER_TEST(TestPoint, Subtraction);
-  REGISTER_TEST(TestPoint, RoundToMultiple);
-}
-
-void TestPoint::Addition() {
-  Point a, b;
-  a.x = 2;
-  a.y = 2;
-  b.x = 5;
-  b.y = -5;
-
-  a += b;
-
-  VERIFY(a.x == 7.f);
-  VERIFY(a.y == -3.f);
-}
-
-void TestPoint::Subtraction() {
-  Point a, b;
-  a.x = 2;
-  a.y = 2;
-  b.x = 5;
-  b.y = -5;
-
-  a -= b;
-
-  VERIFY(a.x == -3.f);
-  VERIFY(a.y == 7.f);
-}
-
-void TestPoint::RoundToMultiple() {
-  const int32_t roundTo = 2;
-
-  IntPoint p(478, -394);
-  VERIFY(p.RoundedToMultiple(roundTo) == p);
-
-  IntPoint p2(478, 393);
-  VERIFY(p2.RoundedToMultiple(roundTo) != p2);
-}

gfx/2d/unittest/TestPoint.h

@@ -1,18 +0,0 @@
-/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
-/* vim: set ts=8 sts=2 et sw=2 tw=80: */
-/* This Source Code Form is subject to the terms of the Mozilla Public
- * License, v. 2.0. If a copy of the MPL was not distributed with this
- * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
-
-#pragma once
-
-#include "TestBase.h"
-
-class TestPoint : public TestBase {
- public:
-  TestPoint();
-
-  void Addition();
-  void Subtraction();
-  void RoundToMultiple();
-};

gfx/tests/gtest/TestMoz2D.cpp

@@ -6,7 +6,6 @@
 
 #include "gtest/gtest.h"
 #include "TestBase.h"
-#include "TestPoint.h"
 #include "TestScaling.h"
 #include "TestBugs.h"
 
@@ -20,16 +19,6 @@ TEST(Moz2D, Bugs)
   ASSERT_EQ(failures, 0);
 }
 
-TEST(Moz2D, Point)
-{
-  TestBase* test = new TestPoint();
-  int failures = 0;
-  test->RunTests(&failures);
-  delete test;
-
-  ASSERT_EQ(failures, 0);
-}
-
 TEST(Moz2D, Scaling)
 {
   TestBase* test = new TestScaling();

gfx/tests/gtest/TestPoint.cpp

@@ -0,0 +1,98 @@
+/* -*- Mode: C++; tab-width: 8; indent-tabs-mode: nil; c-basic-offset: 2 -*- */
+/* vim: set ts=8 sts=2 et sw=2 tw=80: */
+/* This Source Code Form is subject to the terms of the Mozilla Public
+ * License, v. 2.0. If a copy of the MPL was not distributed with this
+ * file, You can obtain one at http://mozilla.org/MPL/2.0/. */
+
+#include "gtest/gtest.h"
+#include <cmath>
+
+#include "BasePoint.h"
+#include "Units.h"
+#include "Point.h"
+
+using mozilla::CSSCoord;
+using mozilla::CSSIntCoord;
+using mozilla::CSSIntPoint;
+using mozilla::CSSPixel;
+using mozilla::gfx::CoordTyped;
+using mozilla::gfx::FloatType_t;
+using mozilla::gfx::IntCoordTyped;
+using mozilla::gfx::IntPointTyped;
+using mozilla::gfx::PointTyped;
+using mozilla::gfx::UnknownUnits;
+
+TEST(Gfx, TestCSSIntPointLength)
+{
+  CSSIntPoint testPnt(1, 1);
+  float res = testPnt.Length();
+
+  float epsilon = 0.001f;
+  constexpr float sqrtOfTwo = 1.414;
+  float diff = std::abs(res - sqrtOfTwo);
+  EXPECT_LT(diff, epsilon);
+}
+
+TEST(Gfx, TestPointAddition)
+{
+  PointTyped<CSSPixel> a, b;
+  a.x = 2;
+  a.y = 2;
+  b.x = 5;
+  b.y = -5;
+
+  a += b;
+
+  EXPECT_EQ(a.x, 7.f);
+  EXPECT_EQ(a.y, -3.f);
+}
+
+TEST(Gfx, TestPointSubtraction)
+{
+  PointTyped<CSSPixel> a, b;
+  a.x = 2;
+  a.y = 2;
+  b.x = 5;
+  b.y = -5;
+
+  a -= b;
+
+  EXPECT_EQ(a.x, -3.f);
+  EXPECT_EQ(a.y, 7.f);
+}
+
+TEST(Gfx, TestPointRoundToMultiple)
+{
+  const int32_t roundTo = 2;
+
+  IntPointTyped<CSSPixel> p(478, -394);
+  EXPECT_EQ(p.RoundedToMultiple(roundTo), p);
+
+  IntPointTyped<CSSPixel> p2(478, 393);
+  EXPECT_NE(p2.RoundedToMultiple(roundTo), p2);
+}
+
+TEST(Gfx, TestFloatTypeMeta)
+{
+  // TODO: Should int64_t's FloatType be double instead?
+  static_assert(std::is_same_v<FloatType_t<int64_t>, float>,
+                "The FloatType of an integer type should be float");
+  static_assert(std::is_same_v<FloatType_t<int32_t>, float>,
+                "The FloatType of an integer type should be float");
+  static_assert(
+      std::is_same_v<FloatType_t<float>, float>,
+      "The FloatType of a floating-point type should be the given type");
+  static_assert(
+      std::is_same_v<FloatType_t<double>, double>,
+      "The FloatType of a floating-point type should be the given type");
+  static_assert(
+      std::is_same_v<FloatType_t<IntCoordTyped<UnknownUnits, int32_t>>,
+                     CoordTyped<UnknownUnits, float>>,
+      "The FloatType of an IntCoordTyped<Units, Rep> should be "
+      "CoordTyped<Units, float>");
+  static_assert(
+      std::is_same_v<FloatType_t<CoordTyped<UnknownUnits, long double>>,
+                     CoordTyped<UnknownUnits, long double>>,
+      "The FloatType of a CoordTyped<Units, Rep> should be "
+      "CoordTyped<Units, Rep>");
+}

gfx/tests/gtest/moz.build

@@ -17,6 +17,7 @@ UNIFIED_SOURCES += [
     "TestGfxWidgets.cpp",
     "TestMatrix.cpp",
     "TestMoz2D.cpp",
+    "TestPoint.cpp",
     "TestPolygon.cpp",
     "TestQcms.cpp",
     "TestRegion.cpp",
@@ -38,7 +39,6 @@ UNIFIED_SOURCES += [
         "TestBase.cpp",
         "TestBugs.cpp",
         "TestCairo.cpp",
-        "TestPoint.cpp",
         "TestScaling.cpp",
     ]
 ]
@@ -65,6 +65,7 @@ LOCAL_INCLUDES += [
     "/gfx/layers",
     "/gfx/ots/src",
     "/gfx/qcms",
+    "/layout/base",
 ]
 
 FINAL_LIBRARY = "xul-gtest"