Add more unit tests for rounding values to pixel grid (#1776)

Summary:
Pull Request resolved: #1776

# Changelog:
[Internal] -

I was looking into some profiling results and noticed that Yoga has some quirky custom logic when it comes to rounding to the pixel grid, especially for the values that are halfway through.

There are already unit tests in place, but those cases weren't covered, so I am adding these extra corner cases here, to make sure they are covered in case that the actual rounding function may get modified (which it might make sense to, as it's currently can be more expensive than it could have been in some scenarios).

Reviewed By: christophpurrer

Differential Revision: D67712673

fbshipit-source-id: da1b7339a8939ced8d91f15441bc7d1f8af768c8

tests/YGRoundingFunctionTest.cpp

@@ -8,6 +8,8 @@
 #include <gtest/gtest.h>
 #include <yoga/Yoga.h>
 
+#include <cmath>
+
 TEST(YogaTest, rounding_value) {
   // Test that whole numbers are rounded to whole despite ceil/floor flags
   ASSERT_FLOAT_EQ(6.0, YGRoundValueToPixelGrid(6.000001, 2.0, false, false));
@@ -39,6 +41,44 @@ TEST(YogaTest, rounding_value) {
   ASSERT_FLOAT_EQ(-6.0, YGRoundValueToPixelGrid(-5.99, 2.0, false, false));
   ASSERT_FLOAT_EQ(-5.5, YGRoundValueToPixelGrid(-5.99, 2.0, true, false));
   ASSERT_FLOAT_EQ(-6.0, YGRoundValueToPixelGrid(-5.99, 2.0, false, true));
+
+  // Rounding up/down halfway values is as expected for both positive and
+  // negative numbers
+  ASSERT_FLOAT_EQ(-3, YGRoundValueToPixelGrid(-3.5, 1.0, false, false));
+  ASSERT_FLOAT_EQ(-3, YGRoundValueToPixelGrid(-3.4, 1.0, false, false));
+  ASSERT_FLOAT_EQ(-4, YGRoundValueToPixelGrid(-3.6, 1.0, false, false));
+  ASSERT_FLOAT_EQ(-3, YGRoundValueToPixelGrid(-3.499999, 1.0, false, false));
+  ASSERT_FLOAT_EQ(-3, YGRoundValueToPixelGrid(-3.500001, 1.0, false, false));
+  ASSERT_FLOAT_EQ(-4, YGRoundValueToPixelGrid(-3.5001, 1.0, false, false));
+
+  ASSERT_FLOAT_EQ(-3, YGRoundValueToPixelGrid(-3.5, 1.0, true, false));
+  ASSERT_FLOAT_EQ(-3, YGRoundValueToPixelGrid(-3.4, 1.0, true, false));
+  ASSERT_FLOAT_EQ(-3, YGRoundValueToPixelGrid(-3.6, 1.0, true, false));
+  ASSERT_FLOAT_EQ(-3, YGRoundValueToPixelGrid(-3.499999, 1.0, true, false));
+  ASSERT_FLOAT_EQ(-3, YGRoundValueToPixelGrid(-3.500001, 1.0, true, false));
+  ASSERT_FLOAT_EQ(-3, YGRoundValueToPixelGrid(-3.5001, 1.0, true, false));
+  ASSERT_FLOAT_EQ(-3, YGRoundValueToPixelGrid(-3.00001, 1.0, true, false));
+  ASSERT_FLOAT_EQ(-3, YGRoundValueToPixelGrid(-3, 1.0, true, false));
+
+  ASSERT_FLOAT_EQ(-4, YGRoundValueToPixelGrid(-3.5, 1.0, false, true));
+  ASSERT_FLOAT_EQ(-4, YGRoundValueToPixelGrid(-3.4, 1.0, false, true));
+  ASSERT_FLOAT_EQ(-4, YGRoundValueToPixelGrid(-3.6, 1.0, false, true));
+  ASSERT_FLOAT_EQ(-4, YGRoundValueToPixelGrid(-3.499999, 1.0, false, true));
+  ASSERT_FLOAT_EQ(-4, YGRoundValueToPixelGrid(-3.500001, 1.0, false, true));
+  ASSERT_FLOAT_EQ(-4, YGRoundValueToPixelGrid(-3.5001, 1.0, false, true));
+  ASSERT_FLOAT_EQ(-3, YGRoundValueToPixelGrid(-3.00001, 1.0, false, true));
+  ASSERT_FLOAT_EQ(-3, YGRoundValueToPixelGrid(-3, 1.0, false, true));
+
+  // NAN is treated as expected:
+  ASSERT_TRUE(std::isnan(YGRoundValueToPixelGrid(
+      std::numeric_limits<double>::quiet_NaN(), 1.5, false, false)));
+  ASSERT_TRUE(std::isnan(YGRoundValueToPixelGrid(
+      1.5, std::numeric_limits<double>::quiet_NaN(), false, false)));
+  ASSERT_TRUE(std::isnan(YGRoundValueToPixelGrid(
+      std::numeric_limits<double>::quiet_NaN(),
+      std::numeric_limits<double>::quiet_NaN(),
+      false,
+      false)));
 }
 
 static YGSize measureText(