[UWP] Fix AdaptiveColumn width (#3340)

With change fee0c03, pixel width and string width in the shared model are now
last-writer-wins. Update `AdaptiveColumn::GetSharedModel()` to account for that.

Fixes #3339.

source/shared/cpp/AdaptiveCardsSharedModel/AdaptiveCardsSharedModelUnitTest/ElementTest.cpp

@@ -0,0 +1,39 @@
+// Copyright (c) Microsoft Corporation. All rights reserved.
+// Licensed under the MIT License.
+#include "stdafx.h"
+#include "Column.h"
+
+using namespace std::string_literals;
+
+using namespace Microsoft::VisualStudio::CppUnitTestFramework;
+using namespace AdaptiveCards;
+
+namespace AdaptiveCardsSharedModelUnitTest
+{
+    TEST_CLASS(ElementTest)
+    {
+    public:
+        TEST_METHOD(ColumnPixelWidthTest)
+        {
+            auto columnTest = std::make_shared<AdaptiveCards::Column>();
+            Assert::AreEqual(0, columnTest->GetPixelWidth());
+            Assert::AreEqual("Auto"s, columnTest->GetWidth());
+            Assert::AreEqual("{\"items\":[],\"type\":\"Column\",\"width\":\"Auto\"}\n"s, columnTest->Serialize());
+
+            columnTest->SetWidth("20px"s);
+            Assert::AreEqual(20, columnTest->GetPixelWidth());
+            Assert::AreEqual("20px"s, columnTest->GetWidth());
+            Assert::AreEqual("{\"items\":[],\"type\":\"Column\",\"width\":\"20px\"}\n"s, columnTest->Serialize());
+
+            columnTest->SetPixelWidth(40);
+            Assert::AreEqual(40, columnTest->GetPixelWidth());
+            Assert::AreEqual("40px"s, columnTest->GetWidth());
+            Assert::AreEqual("{\"items\":[],\"type\":\"Column\",\"width\":\"40px\"}\n"s, columnTest->Serialize());
+
+            columnTest->SetWidth("Stretch");
+            Assert::AreEqual(0, columnTest->GetPixelWidth());
+            Assert::AreEqual("stretch"s, columnTest->GetWidth());
+            Assert::AreEqual("{\"items\":[],\"type\":\"Column\",\"width\":\"stretch\"}\n"s, columnTest->Serialize());
+        }
+    };
+}

source/uwp/Renderer/lib/AdaptiveColumn.cpp

@@ -164,8 +164,16 @@ namespace AdaptiveNamespace
 
         column->SetStyle(static_cast<AdaptiveSharedNamespace::ContainerStyle>(m_style));
         column->SetVerticalContentAlignment(static_cast<AdaptiveSharedNamespace::VerticalContentAlignment>(m_verticalAlignment));
-        column->SetWidth(HStringToUTF8(m_width.Get()));
-        column->SetPixelWidth(m_pixelWidth);
+
+        if (m_pixelWidth)
+        {
+            column->SetPixelWidth(m_pixelWidth);
+        }
+        else
+        {
+            column->SetWidth(HStringToUTF8(m_width.Get()));
+        }
+
         column->SetMinHeight(m_minHeight);
         column->SetBleed(m_bleed);