Compute main dimensions from chidren when not defined

spec/LayoutSpec.js

@@ -71,9 +71,8 @@ function computeDOMLayout(node) {
 function testLayout(node, expectedLayout) {
   var layout = computeLayout(node);
   var domLayout = computeDOMLayout(node);
-  expect(layout).toEqual(expectedLayout)
-  expect(layout).toEqual(domLayout);
   expect(expectedLayout).toEqual(domLayout);
+  expect(layout).toEqual(domLayout);
 }
 
 describe('Layout', function() {
@@ -178,5 +177,21 @@ describe('Layout', function() {
       ]
     });
   });
+
+  it('should layout node based on children main dimensions', function() {
+    testLayout({
+      style: {width: 300},
+      children: [
+        {style: {width: 100, height: 200}},
+        {style: {width: 300, height: 150}}
+      ]
+    }, {
+      width: 300, height: 350, top: 0, left: 0,
+      children: [
+        {width: 100, height: 200, top: 0, left: 0},
+        {width: 300, height: 150, top: 200, left: 0}
+      ]
+    });
+  });
 });
 

src/Layout.js

@@ -40,8 +40,12 @@ function computeLayout(node) {
     var mainAxis = node.style.flexDirection === 'row' ? 'row' : 'column';
     var crossAxis = mainAxis === 'row' ? 'column' : 'row';
 
-    var mainPos = 0;
+    var mainDimInStyle = dim[mainAxis] in node.style;
+    if (mainDimInStyle) {
+      node.layout[dim[mainAxis]] = node.style[dim[mainAxis]];
+    }
 
+    var mainPos = 0;
     var children = [];
     (node.children || []).forEach(function(child) {
       var offset = {};
@@ -52,8 +56,10 @@ function computeLayout(node) {
       mainPos += child.layout[dim[mainAxis]] + 2 * getMargin(child);
     });
 
-    node.layout.width = node.style.width;
-    node.layout.height = node.style.height;
+    if (!mainDimInStyle) {
+      node.layout[dim[mainAxis]] = mainPos;
+    }
+    node.layout[dim[crossAxis]] = node.style[dim[crossAxis]];
     node.layout.top = getMargin(node) + parent.top;
     node.layout.left = getMargin(node) + parent.left;
   }