Fix flooring of border

tests/StyleTest.cpp

@@ -0,0 +1,44 @@
+/*
+ * Copyright (c) Meta Platforms, Inc. and affiliates.
+ *
+ * This source code is licensed under the MIT license found in the
+ * LICENSE file in the root directory of this source tree.
+ */
+
+#include <gtest/gtest.h>
+#include <yoga/style/Style.h>
+
+namespace facebook::yoga {
+
+TEST(Style, computed_padding_is_floored) {
+  yoga::Style style;
+  style.setPadding(Edge::All, value::points(-1.0f));
+  auto paddingStart = style.computeInlineStartPadding(
+      FlexDirection::Row, Direction::LTR, 0.0f /*widthSize*/);
+  ASSERT_EQ(paddingStart, 0.0f);
+}
+
+TEST(Style, computed_border_is_floored) {
+  yoga::Style style;
+  style.setBorder(Edge::All, value::points(-1.0f));
+  auto borderStart =
+      style.computeInlineStartBorder(FlexDirection::Row, Direction::LTR);
+  ASSERT_EQ(borderStart, 0.0f);
+}
+
+TEST(Style, computed_gap_is_floored) {
+  yoga::Style style;
+  style.setGap(Gutter::Column, value::points(-1.0f));
+  auto gapBetweenColumns = style.computeGapForAxis(FlexDirection::Row);
+  ASSERT_EQ(gapBetweenColumns, 0.0f);
+}
+
+TEST(Style, computed_margin_is_not_floored) {
+  yoga::Style style;
+  style.setMargin(Edge::All, value::points(-1.0f));
+  auto marginStart = style.computeInlineStartMargin(
+      FlexDirection::Row, Direction::LTR, 0.0f /*widthSize*/);
+  ASSERT_EQ(marginStart, -1.0f);
+}
+
+} // namespace facebook::yoga

yoga/style/Style.h

@@ -312,28 +312,32 @@ class YG_EXPORT Style {
   }
 
   float computeFlexStartBorder(FlexDirection axis, Direction direction) const {
-    return computeBorder(flexStartEdge(axis), direction)
-        .resolve(0.0f)
-        .unwrapOrDefault(0.0f);
+    return maxOrDefined(
+        computeBorder(flexStartEdge(axis), direction).resolve(0.0f).unwrap(),
+        0.0f);
   }
 
   float computeInlineStartBorder(FlexDirection axis, Direction direction)
       const {
-    return computeBorder(inlineStartEdge(axis, direction), direction)
-        .resolve(0.0f)
-        .unwrapOrDefault(0.0f);
+    return maxOrDefined(
+        computeBorder(inlineStartEdge(axis, direction), direction)
+            .resolve(0.0f)
+            .unwrap(),
+        0.0f);
   }
 
   float computeFlexEndBorder(FlexDirection axis, Direction direction) const {
-    return computeBorder(flexEndEdge(axis), direction)
-        .resolve(0.0f)
-        .unwrapOrDefault(0.0f);
+    return maxOrDefined(
+        computeBorder(flexEndEdge(axis), direction).resolve(0.0f).unwrap(),
+        0.0f);
   }
 
   float computeInlineEndBorder(FlexDirection axis, Direction direction) const {
-    return computeBorder(inlineEndEdge(axis, direction), direction)
-        .resolve(0.0f)
-        .unwrapOrDefault(0.0f);
+    return maxOrDefined(
+        computeBorder(inlineEndEdge(axis, direction), direction)
+            .resolve(0.0f)
+            .unwrap(),
+        0.0f);
   }
 
   float computeFlexStartPadding(