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Fixed rounding issues with YGRoundValueToPixelGrid and negative floats #702

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Fixed rounding issues with YGRoundValueToPixelGrid and negative floats #702

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df9b984
Fixed rounding issues with YGRoundValueToPixelGrid and negative floats
Jan 24, 2018
86a7fff
Merge branch 'master' into edensan
Edensan Mar 14, 2018
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49 changes: 49 additions & 0 deletions tests/YGRoundingFunctionTest.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -20,11 +20,60 @@ TEST(YogaTest, rounding_value) {
ASSERT_FLOAT_EQ(6.0, YGRoundValueToPixelGrid(5.999999, 2.0, true, false));
ASSERT_FLOAT_EQ(6.0, YGRoundValueToPixelGrid(5.999999, 2.0, false, true));

// Test with negative numbers
ASSERT_FLOAT_EQ(-6.0, YGRoundValueToPixelGrid(-6.000001, 2.0, false, false));
ASSERT_FLOAT_EQ(-6.0, YGRoundValueToPixelGrid(-6.000001, 2.0, true, false));
ASSERT_FLOAT_EQ(-6.0, YGRoundValueToPixelGrid(-6.000001, 2.0, false, true));
ASSERT_FLOAT_EQ(-6.0, YGRoundValueToPixelGrid(-5.999999, 2.0, false, false));
ASSERT_FLOAT_EQ(-6.0, YGRoundValueToPixelGrid(-5.999999, 2.0, true, false));
ASSERT_FLOAT_EQ(-6.0, YGRoundValueToPixelGrid(-5.999999, 2.0, false, true));

// Test that numbers with fraction are rounded correctly accounting for ceil/floor flags
ASSERT_FLOAT_EQ(6.0, YGRoundValueToPixelGrid(6.01, 2.0, false, false));
ASSERT_FLOAT_EQ(6.5, YGRoundValueToPixelGrid(6.01, 2.0, true, false));
ASSERT_FLOAT_EQ(6.0, YGRoundValueToPixelGrid(6.01, 2.0, false, true));
ASSERT_FLOAT_EQ(6.0, YGRoundValueToPixelGrid(5.99, 2.0, false, false));
ASSERT_FLOAT_EQ(6.0, YGRoundValueToPixelGrid(5.99, 2.0, true, false));
ASSERT_FLOAT_EQ(5.5, YGRoundValueToPixelGrid(5.99, 2.0, false, true));
ASSERT_FLOAT_EQ(6.0, YGRoundValueToPixelGrid(6.49, 1.0, false, false));
ASSERT_FLOAT_EQ(7.0, YGRoundValueToPixelGrid(6.50, 1.0, false, false));
ASSERT_FLOAT_EQ(7.0, YGRoundValueToPixelGrid(6.51, 1.0, false, false));
ASSERT_FLOAT_EQ(7.0, YGRoundValueToPixelGrid(6.50, 1.0, true, false));
ASSERT_FLOAT_EQ(6.0, YGRoundValueToPixelGrid(6.50, 1.0, false, true));

// Test with negative numbers
ASSERT_FLOAT_EQ(-6.0, YGRoundValueToPixelGrid(-6.01, 2.0, false, false));
ASSERT_FLOAT_EQ(-6.0, YGRoundValueToPixelGrid(-6.01, 2.0, true, false));
ASSERT_FLOAT_EQ(-6.5, YGRoundValueToPixelGrid(-6.01, 2.0, false, true));
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));
ASSERT_FLOAT_EQ(-6.0, YGRoundValueToPixelGrid(-6.49, 1.0, false, false));
ASSERT_FLOAT_EQ(-6.0, YGRoundValueToPixelGrid(-6.50, 1.0, false, false));
ASSERT_FLOAT_EQ(-7.0, YGRoundValueToPixelGrid(-6.51, 1.0, false, false));
ASSERT_FLOAT_EQ(-6.0, YGRoundValueToPixelGrid(-6.50, 1.0, true, false));
ASSERT_FLOAT_EQ(-7.0, YGRoundValueToPixelGrid(-6.50, 1.0, false, true));

// Do a simple translation test to ensure that a distance between 2 values
// stays consistent during an animation, even after rounding them.
const int LAPS = 3;
const int LAP_CLOSEST = 0;
const int LAP_CEIL = 1;
const int LAP_FLOOR = 2;
for (int currentLap = LAP_CLOSEST; currentLap < LAPS; ++currentLap)
{
float left = -2.0f;
float right = 2.0f;
const float distance = right-left;
float totalDistance = 1.1f;
const float step = 0.01f;
while (totalDistance >= 0.0f) {
left += step;
right += step;
const float snappedLeft = YGRoundValueToPixelGrid(left, 1.0, currentLap==LAP_CEIL, currentLap==LAP_FLOOR);
const float snappedRight = YGRoundValueToPixelGrid(right, 1.0, currentLap==LAP_CEIL, currentLap==LAP_FLOOR);
ASSERT_FLOAT_EQ(distance, (snappedRight-snappedLeft));
totalDistance -= step;
}
}
}
44 changes: 32 additions & 12 deletions yoga/Yoga.cpp
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Expand Up @@ -2928,21 +2928,41 @@ float YGRoundValueToPixelGrid(const float value,
const bool forceCeil,
const bool forceFloor) {
float scaledValue = value * pointScaleFactor;
float fractial = fmodf(scaledValue, 1.0);
if (YGFloatsEqual(fractial, 0)) {
// First we check if the value is already rounded
scaledValue = scaledValue - fractial;
} else if (YGFloatsEqual(fractial, 1.0)) {
scaledValue = scaledValue - fractial + 1.0;
const float fractial = fmodf(scaledValue, 1.0f);
const float absoluteFractial = fabs(fractial);

// 1. Remove any remainder from the scaledValue
scaledValue = scaledValue - fractial;

// 2. Figure out rounding
// Note: It is important that the following rounding algorithm
// ensures that both positive and negative values are treated exactly the same.
if (YGFloatsEqual(absoluteFractial, 0.0f)) {
// Already whole (or close enough), skip rounding
} else if (YGFloatsEqual(absoluteFractial, 1.0f)) {
// Already whole (or close enough), skip rounding
scaledValue += (fractial < 0.0f) ? -1.0f : 1.0f;
} else if (forceCeil) {
// Next we check if we need to use forced rounding
scaledValue = scaledValue - fractial + 1.0f;
// Force round to upper whole value
if (fractial > 0.0f) {
scaledValue += 1.0f;
}
} else if (forceFloor) {
scaledValue = scaledValue - fractial;
// Force round to lower whole value
if (fractial < 0.0f) {
scaledValue -= 1.0f;
}
} else {
// Finally we just round the value
scaledValue = scaledValue - fractial +
(fractial > 0.5f || YGFloatsEqual(fractial, 0.5f) ? 1.0f : 0.0f);
// Round to closest whole value
if (fractial > 0.0f) {
if (absoluteFractial > 0.5f || YGFloatsEqual(absoluteFractial, 0.5f)) {
scaledValue += 1.0f;
}
} else {
if (absoluteFractial > 0.5f && !YGFloatsEqual(absoluteFractial, 0.5f)) {
scaledValue -= 1.0f;
}
}
}
return scaledValue / pointScaleFactor;
}
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