[NUI] Measure Child's Layout in FlexLayout (#1385)

Previously, children in FlexLayout were not measured but just returning NaturalSize.
To support nested Layout, FlexLayout also should measure Layout of its children.

Now, FlexLayout measures its children and it also can fix MatchParent issue in FlexLayout.

diff --git a/src/Tizen.NUI/src/public/Layouting/FlexLayout.cs b/src/Tizen.NUI/src/public/Layouting/FlexLayout.cs
index 12713c6..1acbd86 100755 (executable)
--- a/src/Tizen.NUI/src/public/Layouting/FlexLayout.cs
+++ b/src/Tizen.NUI/src/public/Layouting/FlexLayout.cs
@@ -39,6 +39,9 @@ namespace Tizen.NUI
         private bool disposed;
         private bool isDisposeQueued = false;
 
+        private MeasureSpecification parentMeasureSpecificationWidth;
+        private MeasureSpecification parentMeasureSpecificationHeight;
+
         private IntPtr _rootFlex;  // Pointer to the unmanged flex layout class.
 
         internal const float FlexUndefined = 10E20F; // Auto setting which is equivalent to WrapContent.
@@ -398,27 +401,24 @@ namespace Tizen.NUI
             Stretch
         }
 
-        private MeasuredSize measureChild(global::System.IntPtr child, float width, int measureModeWidth, float height, int measureModeHeight)
+        private MeasuredSize measureChild(global::System.IntPtr childPtr, float width, int measureModeWidth, float height, int measureModeHeight)
         {
-            View view = Registry.GetManagedBaseHandleFromNativePtr(child) as View;
-            Size2D viewSize = new Size2D(8,8);
-            if(view)
-            {
-                viewSize = view.Size2D;
-            }
+            // We need to measure child layout
+            View child = Registry.GetManagedBaseHandleFromNativePtr(childPtr) as View;
 
-            // If size not set on child then use NaturalSize
-            if(viewSize.Width ==0 && viewSize.Height==0)
-            {
-                viewSize = view.NaturalSize2D;
-            }
+            LayoutItem childLayout = child.Layout;
+
+            MeasureSpecification childWidthMeasureSpec = GetChildMeasureSpecification(parentMeasureSpecificationWidth,
+                                    new LayoutLength(childLayout.Padding.Start + childLayout.Padding.End),
+                                    new LayoutLength(child.WidthSpecification));
 
-            Debug.WriteLineIf( LayoutDebugFlex, "FlexLayout measureChild View:" + view.Name
-                                               + "Size:" + viewSize.Width
-                                               + ","
-                                               + viewSize.Height);
+            MeasureSpecification childHeightMeasureSpec = GetChildMeasureSpecification(parentMeasureSpecificationHeight,
+                                    new LayoutLength(childLayout.Padding.Top + childLayout.Padding.Bottom),
+                                    new LayoutLength(child.HeightSpecification));
 
-            return new MeasuredSize(viewSize.Width,viewSize.Height);
+            childLayout.Measure( childWidthMeasureSpec, childHeightMeasureSpec);
+
+            return new MeasuredSize(childLayout.MeasuredWidth.Size.AsRoundedValue(),childLayout.MeasuredHeight.Size.AsRoundedValue());
         }
 
         void InsertChild( LayoutItem child )
@@ -478,6 +478,12 @@ namespace Tizen.NUI
                 height = heightMeasureSpec.Size.AsDecimal();
             }
 
+            // Save measureSpec to measure children.
+            // In other Layout, we can pass it as parameter to measuring child but in FlexLayout we can't
+            // because measurChild function is called by native callback.
+            parentMeasureSpecificationWidth = widthMeasureSpec;
+            parentMeasureSpecificationHeight = heightMeasureSpec;
+
             Interop.FlexLayout.FlexLayout_CalculateLayout( swigCPtr, width, height, isLayoutRtl );
 
             LayoutLength flexLayoutWidth =  new LayoutLength( Interop.FlexLayout.FlexLayout_GetWidth(swigCPtr) );