Overflow detection in Yoga

Summary:
We need to provide Yoga clients with means of detecting overflow in flexbox layout. This information can be used later to identify a non-overflowing layout variant among others.

Flexbox layout considered overflown if (this is *not* an exhaustive list):

- if any child node overflows
- [no-wrap] total flex basis of all child nodes is greater than available space in parent and there are no flexible children
- [no-wrap] after flexing there is still not enough space to layout all child nodes

Reviewed By: gkassabli

Differential Revision: D5336645

fbshipit-source-id: c4f87d1754d7bac848e8d347b31d619393b94d2c

tests/YGHadOverflowTest.cpp

@@ -0,0 +1,103 @@
+// Copyright 2004-present Facebook. All Rights Reserved.
+
+#include <gtest/gtest.h>
+#include <yoga/Yoga.h>
+
+using namespace ::testing;
+
+class YogaTest_HadOverflowTests : public Test {
+protected:
+  YogaTest_HadOverflowTests() {
+    config = YGConfigNew();
+    root = YGNodeNewWithConfig(config);
+    YGNodeStyleSetWidth(root, 200);
+    YGNodeStyleSetHeight(root, 100);
+    YGNodeStyleSetFlexDirection(root, YGFlexDirectionColumn);
+    YGNodeStyleSetFlexWrap(root, YGWrapNoWrap);
+  }
+
+  ~YogaTest_HadOverflowTests() {
+    YGNodeFreeRecursive(root);
+    YGConfigFree(config);
+  }
+
+  YGNodeRef root;
+  YGConfigRef config;
+};
+
+TEST_F(YogaTest_HadOverflowTests, children_overflow_no_wrap_and_no_flex_children) {
+  const YGNodeRef child0 = YGNodeNewWithConfig(config);
+  YGNodeStyleSetWidth(child0, 80);
+  YGNodeStyleSetHeight(child0, 40);
+  YGNodeStyleSetMargin(child0, YGEdgeTop, 10);
+  YGNodeStyleSetMargin(child0, YGEdgeBottom, 15);
+  YGNodeInsertChild(root, child0, 0);
+  const YGNodeRef child1 = YGNodeNewWithConfig(config);
+  YGNodeStyleSetWidth(child1, 80);
+  YGNodeStyleSetHeight(child1, 40);
+  YGNodeStyleSetMargin(child1, YGEdgeBottom, 5);
+  YGNodeInsertChild(root, child1, 1);
+
+  YGNodeCalculateLayout(root, 200, 100, YGDirectionLTR);
+
+  ASSERT_TRUE(YGNodeLayoutGetHadOverflow(root));
+}
+
+TEST_F(YogaTest_HadOverflowTests, spacing_overflow_no_wrap_and_no_flex_children) {
+  const YGNodeRef child0 = YGNodeNewWithConfig(config);
+  YGNodeStyleSetWidth(child0, 80);
+  YGNodeStyleSetHeight(child0, 40);
+  YGNodeStyleSetMargin(child0, YGEdgeTop, 10);
+  YGNodeStyleSetMargin(child0, YGEdgeBottom, 10);
+  YGNodeInsertChild(root, child0, 0);
+  const YGNodeRef child1 = YGNodeNewWithConfig(config);
+  YGNodeStyleSetWidth(child1, 80);
+  YGNodeStyleSetHeight(child1, 40);
+  YGNodeStyleSetMargin(child1, YGEdgeBottom, 5);
+  YGNodeInsertChild(root, child1, 1);
+
+  YGNodeCalculateLayout(root, 200, 100, YGDirectionLTR);
+
+  ASSERT_TRUE(YGNodeLayoutGetHadOverflow(root));
+}
+
+TEST_F(YogaTest_HadOverflowTests, no_overflow_no_wrap_and_flex_children) {
+  const YGNodeRef child0 = YGNodeNewWithConfig(config);
+  YGNodeStyleSetWidth(child0, 80);
+  YGNodeStyleSetHeight(child0, 40);
+  YGNodeStyleSetMargin(child0, YGEdgeTop, 10);
+  YGNodeStyleSetMargin(child0, YGEdgeBottom, 10);
+  YGNodeInsertChild(root, child0, 0);
+  const YGNodeRef child1 = YGNodeNewWithConfig(config);
+  YGNodeStyleSetWidth(child1, 80);
+  YGNodeStyleSetHeight(child1, 40);
+  YGNodeStyleSetMargin(child1, YGEdgeBottom, 5);
+  YGNodeStyleSetFlexShrink(child1, 1);
+  YGNodeInsertChild(root, child1, 1);
+
+  YGNodeCalculateLayout(root, 200, 100, YGDirectionLTR);
+
+  ASSERT_FALSE(YGNodeLayoutGetHadOverflow(root));
+}
+
+TEST_F(YogaTest_HadOverflowTests, spacing_overflow_in_nested_nodes) {
+  const YGNodeRef child0 = YGNodeNewWithConfig(config);
+  YGNodeStyleSetWidth(child0, 80);
+  YGNodeStyleSetHeight(child0, 40);
+  YGNodeStyleSetMargin(child0, YGEdgeTop, 10);
+  YGNodeStyleSetMargin(child0, YGEdgeBottom, 10);
+  YGNodeInsertChild(root, child0, 0);
+  const YGNodeRef child1 = YGNodeNewWithConfig(config);
+  YGNodeStyleSetWidth(child1, 80);
+  YGNodeStyleSetHeight(child1, 40);
+  YGNodeInsertChild(root, child1, 1);
+  const YGNodeRef child1_1 = YGNodeNewWithConfig(config);
+  YGNodeStyleSetWidth(child1_1, 80);
+  YGNodeStyleSetHeight(child1_1, 40);
+  YGNodeStyleSetMargin(child1_1, YGEdgeBottom, 5);
+  YGNodeInsertChild(child1, child1_1, 0);
+
+  YGNodeCalculateLayout(root, 200, 100, YGDirectionLTR);
+
+  ASSERT_TRUE(YGNodeLayoutGetHadOverflow(root));
+}

yoga/Yoga.c

@@ -54,6 +54,7 @@ typedef struct YGLayout {
 
   uint32_t computedFlexBasisGeneration;
   float computedFlexBasis;
+  bool hadOverflow;
 
   // Instead of recomputing the entire layout every single time, we
   // cache some information to break early when nothing changed
@@ -192,6 +193,7 @@ static YGNode gYGNodeDefaults = {
             .lastParentDirection = (YGDirection) -1,
             .nextCachedMeasurementsIndex = 0,
             .computedFlexBasis = YGUndefined,
+            .hadOverflow = false,
             .measuredDimensions = YG_DEFAULT_DIMENSION_VALUES,
 
             .cachedLayout =
@@ -782,6 +784,7 @@ YG_NODE_LAYOUT_PROPERTY_IMPL(float, Bottom, position[YGEdgeBottom]);
 YG_NODE_LAYOUT_PROPERTY_IMPL(float, Width, dimensions[YGDimensionWidth]);
 YG_NODE_LAYOUT_PROPERTY_IMPL(float, Height, dimensions[YGDimensionHeight]);
 YG_NODE_LAYOUT_PROPERTY_IMPL(YGDirection, Direction, direction);
+YG_NODE_LAYOUT_PROPERTY_IMPL(bool, HadOverflow, hadOverflow);
 
 YG_NODE_LAYOUT_RESOLVED_PROPERTY_IMPL(float, Margin, margin);
 YG_NODE_LAYOUT_RESOLVED_PROPERTY_IMPL(float, Border, border);
@@ -2574,12 +2577,14 @@ static void YGNodelayoutImpl(const YGNodeRef node,
                              performLayout && !requiresStretchLayout,
                              "flex",
                              config);
+        node->layout.hadOverflow = node->layout.hadOverflow || currentRelativeChild->layout.hadOverflow;
 
         currentRelativeChild = currentRelativeChild->nextChild;
       }
     }
 
     remainingFreeSpace = originalRemainingFreeSpace + deltaFreeSpace;
+    node->layout.hadOverflow = node->layout.hadOverflow || (remainingFreeSpace < 0);
 
     // STEP 6: MAIN-AXIS JUSTIFICATION & CROSS-AXIS SIZE DETERMINATION
 

yoga/Yoga.h

@@ -215,6 +215,7 @@ YG_NODE_LAYOUT_PROPERTY(float, Bottom);
 YG_NODE_LAYOUT_PROPERTY(float, Width);
 YG_NODE_LAYOUT_PROPERTY(float, Height);
 YG_NODE_LAYOUT_PROPERTY(YGDirection, Direction);
+YG_NODE_LAYOUT_PROPERTY(bool, HadOverflow);
 
 // Get the computed values for these nodes after performing layout. If they were set using
 // point values then the returned value will be the same as YGNodeStyleGetXXX. However if