C# Baseline function

Summary:
same as Measure function, based on #317
Closes https://github.com/facebook/yoga/pull/321

Reviewed By: emilsjolander

Differential Revision: D4385336

Pulled By: splhack

fbshipit-source-id: b583ec79861d2e9abba31a72503e2f706bfda8e8

csharp/Facebook.Yoga/BaselineFunction.cs

@@ -0,0 +1,13 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+namespace Facebook.Yoga
+{
+    public delegate float BaselineFunction(YogaNode node, float width, float height);
+}

csharp/Facebook.Yoga/Facebook.Yoga.Shared.projitems

@@ -9,12 +9,14 @@
     <Import_RootNamespace>Facebook.Yoga.Shared</Import_RootNamespace>
   </PropertyGroup>
   <ItemGroup>
+    <Compile Include="$(MSBuildThisFileDirectory)BaselineFunction.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Border.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)MeasureFunction.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)MeasureOutput.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Native.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)Spacing.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)YogaAlign.cs" />
+    <Compile Include="$(MSBuildThisFileDirectory)YogaBaselineFunc.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)YogaConstants.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)YogaDimension.cs" />
     <Compile Include="$(MSBuildThisFileDirectory)YogaDirection.cs" />

csharp/Facebook.Yoga/Native.cs

@@ -104,8 +104,9 @@ namespace Facebook.Yoga
             [MarshalAs(UnmanagedType.FunctionPtr)] YogaMeasureFunc measureFunc);
 
         [DllImport(DllName, ExactSpelling = true, CallingConvention = CallingConvention.Cdecl)]
-        [return: MarshalAs(UnmanagedType.FunctionPtr)]
-        public static extern YogaMeasureFunc YGNodeGetMeasureFunc(YGNodeHandle node);
+        public static extern void YGNodeSetBaselineFunc(
+            YGNodeHandle node,
+            [MarshalAs(UnmanagedType.FunctionPtr)] YogaBaselineFunc baselineFunc);
 
         [DllImport(DllName, ExactSpelling = true, CallingConvention = CallingConvention.Cdecl)]
         public static extern void YGNodeSetHasNewLayout(YGNodeHandle node, [MarshalAs(UnmanagedType.I1)] bool hasNewLayout);

csharp/Facebook.Yoga/YogaBaselineFunc.cs

@@ -0,0 +1,17 @@
+/**
+ * Copyright (c) 2014-present, Facebook, Inc.
+ * All rights reserved.
+ *
+ * This source code is licensed under the BSD-style license found in the
+ * LICENSE file in the root directory of this source tree. An additional grant
+ * of patent rights can be found in the PATENTS file in the same directory.
+ */
+
+using System;
+using System.Runtime.InteropServices;
+
+namespace Facebook.Yoga
+{
+    [UnmanagedFunctionPointer(CallingConvention.Cdecl)]
+    public delegate float YogaBaselineFunc(IntPtr node, float width, float height);
+}

csharp/Facebook.Yoga/YogaNode.cs

@@ -21,6 +21,8 @@ namespace Facebook.Yoga
         private List<YogaNode> _children;
         private MeasureFunction _measureFunction;
         private YogaMeasureFunc _ygMeasureFunc;
+        private BaselineFunction _baselineFunction;
+        private YogaBaselineFunc _ygBaselineFunc;
         private object _data;
 
         public YogaNode()
@@ -37,6 +39,7 @@ namespace Facebook.Yoga
         public void Reset()
         {
             _measureFunction = null;
+            _baselineFunction = null;
             _data = null;
 
             Native.YGNodeReset(_ygNode);
@@ -84,6 +87,14 @@ namespace Facebook.Yoga
             }
         }
 
+        public bool IsBaselineDefined
+        {
+            get
+            {
+                return _baselineFunction != null;
+            }
+        }
+
         public void CopyStyle(YogaNode srcNode)
         {
             Native.YGNodeCopyStyle(_ygNode, srcNode._ygNode);
@@ -585,6 +596,13 @@ namespace Facebook.Yoga
             Native.YGNodeSetMeasureFunc(_ygNode, _ygMeasureFunc);
         }
 
+        public void SetBaselineFunction(BaselineFunction baselineFunction)
+        {
+            _baselineFunction = baselineFunction;
+            _ygBaselineFunc = baselineFunction != null ? BaselineInternal : (YogaBaselineFunc)null;
+            Native.YGNodeSetBaselineFunc(_ygNode, _ygBaselineFunc);
+        }
+
         public void CalculateLayout()
         {
             Native.YGNodeCalculateLayout(
@@ -609,6 +627,16 @@ namespace Facebook.Yoga
             return _measureFunction(this, width, widthMode, height, heightMode);
         }
 
+        private float BaselineInternal(IntPtr node, float width, float height)
+        {
+            if (_baselineFunction == null)
+            {
+                throw new InvalidOperationException("Baseline function is not defined.");
+            }
+
+            return _baselineFunction(this, width, height);
+        }
+
         public string Print(YogaPrintOptions options =
             YogaPrintOptions.Layout|YogaPrintOptions.Style|YogaPrintOptions.Children)
         {

csharp/tests/Facebook.Yoga/YogaNodeTest.cs

@@ -197,6 +197,54 @@ namespace Facebook.Yoga
             });
         }
 
+        [Test]
+        public void TestBaselineFunc()
+        {
+            YogaNode node = new YogaNode();
+            node.Height = 200;
+            node.FlexDirection = YogaFlexDirection.Row;
+            node.AlignItems = YogaAlign.Baseline;
+
+            YogaNode child0 = new YogaNode();
+            child0.Width = 100;
+            child0.Height = 110;
+            child0.SetBaselineFunction((_, width, height) => {
+                Assert.AreEqual(100, width);
+                Assert.AreEqual(110, height);
+                return 65;
+            });
+            node.Insert(0, child0);
+
+            YogaNode child1 = new YogaNode();
+            child1.Width = 100;
+            child1.Height = 110;
+            child1.SetBaselineFunction((_, width, height) => {
+                Assert.AreEqual(100, width);
+                Assert.AreEqual(110, height);
+                return 80;
+            });
+            node.Insert(1, child1);
+
+            YogaNode child2 = new YogaNode();
+            child2.Width = 100;
+            child2.Height = 110;
+            child2.SetBaselineFunction((_, width, height) => {
+                Assert.AreEqual(100, width);
+                Assert.AreEqual(110, height);
+                return 88;
+            });
+            node.Insert(2, child2);
+
+            node.CalculateLayout();
+
+            Assert.AreEqual(0, child0.LayoutX);
+            Assert.AreEqual(23, child0.LayoutY);
+            Assert.AreEqual(100, child1.LayoutX);
+            Assert.AreEqual(8, child1.LayoutY);
+            Assert.AreEqual(200, child2.LayoutX);
+            Assert.AreEqual(0, child2.LayoutY);
+        }
+
         [Test]
         public void TestPrint()
         {