Update align-content handling of overflow (facebook#43752)

Summary:
Pull Request resolved: facebook#43752

Gentest tests started failing because Chrome changed behavior of overflowed align-content container. Spec says should fallback to "safe center", which is really just "start", instead of previous "center" behavior. This changes behavior accordingly.

There is one bit where I think we are doing the wrong thing wrt alignment of flex start vs start (which we don't support yet), but couldn't repro a failing chrome test.

Changelog: [Internal]

Reviewed By: joevilches

Differential Revision: D55617689

fbshipit-source-id: 08f23d198c75f2c2f51ccaa8795289e6e4a92cb8

packages/react-native/ReactCommon/yoga/yoga/algorithm/CalculateLayout.cpp

@@ -1745,41 +1745,50 @@ static void calculateLayoutImpl(
         paddingAndBorderAxisCross;
 
     const float remainingAlignContentDim = innerCrossDim - totalLineCrossDim;
-    switch (node->style().alignContent()) {
+
+    // Apply fallback alignments on overflow
+    // https://www.w3.org/TR/css-align-3/#distribution-values
+    const auto appliedAlignContent =
+        remainingAlignContentDim >= 0 ? node->style().alignContent() : [&]() {
+          switch (node->style().alignContent()) {
+            // Fallback to flex-start
+            case Align::SpaceBetween:
+            case Align::Stretch:
+              return Align::FlexStart;
+
+            // Fallback to safe center. TODO: This should be aligned to Start
+            // instead of FlexStart (for row-reverse containers)
+            case Align::SpaceAround:
+            case Align::SpaceEvenly:
+              return Align::FlexStart;
+            default:
+              return node->style().alignContent();
+          }
+        }();
+
+    switch (appliedAlignContent) {
       case Align::FlexEnd:
         currentLead += remainingAlignContentDim;
         break;
       case Align::Center:
         currentLead += remainingAlignContentDim / 2;
         break;
       case Align::Stretch:
-        if (innerCrossDim > totalLineCrossDim) {
-          leadPerLine =
-              remainingAlignContentDim / static_cast<float>(lineCount);
-        }
+        leadPerLine = remainingAlignContentDim / static_cast<float>(lineCount);
         break;
       case Align::SpaceAround:
-        if (innerCrossDim > totalLineCrossDim) {
-          currentLead +=
-              remainingAlignContentDim / (2 * static_cast<float>(lineCount));
-          leadPerLine =
-              remainingAlignContentDim / static_cast<float>(lineCount);
-        } else {
-          currentLead += remainingAlignContentDim / 2;
-        }
+        currentLead +=
+            remainingAlignContentDim / (2 * static_cast<float>(lineCount));
+        leadPerLine = remainingAlignContentDim / static_cast<float>(lineCount);
         break;
       case Align::SpaceEvenly:
-        if (innerCrossDim > totalLineCrossDim) {
-          currentLead +=
-              remainingAlignContentDim / static_cast<float>(lineCount + 1);
-          leadPerLine =
-              remainingAlignContentDim / static_cast<float>(lineCount + 1);
-        } else {
-          currentLead += remainingAlignContentDim / 2;
-        }
+        currentLead +=
+            remainingAlignContentDim / static_cast<float>(lineCount + 1);
+        leadPerLine =
+            remainingAlignContentDim / static_cast<float>(lineCount + 1);
         break;
       case Align::SpaceBetween:
-        if (innerCrossDim > totalLineCrossDim && lineCount > 1) {
+        if (lineCount > 1) {
           leadPerLine =
               remainingAlignContentDim / static_cast<float>(lineCount - 1);
         }