Rounding error in width/height fixed

Summary: If the width has an exact dimension, while the left and right edges have a decimal part, that means the decimal part is equal and we can round both down instead of rounding left down and right up. Same for top and bottom.

Reviewed By: emilsjolander

Differential Revision:
D5209073

Tags: accept2ship

fbshipit-source-id: a3a6a43767aa707ebfa5eee62a83adcdd88d7ce6

yoga/Yoga.c

@@ -3456,11 +3456,22 @@ static void YGRoundToPixelGrid(const YGNodeRef node,
   node->layout.position[YGEdgeTop] =
       YGRoundValueToPixelGrid(nodeTop, pointScaleFactor, false, textRounding);
 
+  const bool hasFractionalWidth = !YGFloatsEqual(fmodf(nodeWidth, 1.0), 0);
+  const bool hasFractionalHeight = !YGFloatsEqual(fmodf(nodeHeight, 1.0), 0);
+
   node->layout.dimensions[YGDimensionWidth] =
-      YGRoundValueToPixelGrid(absoluteNodeRight, pointScaleFactor, textRounding, false) -
+      YGRoundValueToPixelGrid(
+          absoluteNodeRight,
+          pointScaleFactor,
+          (textRounding && hasFractionalWidth),
+          (textRounding && !hasFractionalWidth)) -
       YGRoundValueToPixelGrid(absoluteNodeLeft, pointScaleFactor, false, textRounding);
   node->layout.dimensions[YGDimensionHeight] =
-      YGRoundValueToPixelGrid(absoluteNodeBottom, pointScaleFactor, textRounding, false) -
+      YGRoundValueToPixelGrid(
+          absoluteNodeBottom,
+          pointScaleFactor,
+          (textRounding && hasFractionalHeight),
+          (textRounding && !hasFractionalHeight)) -
       YGRoundValueToPixelGrid(absoluteNodeTop, pointScaleFactor, false, textRounding);
 
   const uint32_t childCount = YGNodeListCount(node->children);