From 96b64c0e2d98e26dd1a66df9a8536307d849730d Mon Sep 17 00:00:00 2001
From: T Paine <tpaine@microsoft.com>
Date: Tue, 17 Sep 2019 08:57:17 -0700
Subject: [PATCH] TabView: Fix for terminal handling scrollviewer load issue
 (#1339)

---
 dev/TabView/TabView.cpp   | 16 +++++++++++-----
 dev/dll/SharedHelpers.cpp |  8 ++++++++
 dev/inc/SharedHelpers.h   |  2 ++
 3 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/dev/TabView/TabView.cpp b/dev/TabView/TabView.cpp
index e410136e2e..521e1ca34a 100644
--- a/dev/TabView/TabView.cpp
+++ b/dev/TabView/TabView.cpp
@@ -237,14 +237,20 @@ void TabView::OnListViewLoaded(const winrt::IInspectable&, const winrt::RoutedEv
         SelectedIndex(listView.SelectedIndex());
         SelectedItem(listView.SelectedItem());
 
-        m_scrollViewer.set([this, listView]() {
-            auto scrollViewer = SharedHelpers::FindInVisualTreeByName(listView, L"ScrollViewer").as<winrt::FxScrollViewer>();
-            if (scrollViewer)
+        auto scrollViewer = SharedHelpers::FindInVisualTreeByName(listView, L"ScrollViewer").as<winrt::FxScrollViewer>();
+        m_scrollViewer.set(scrollViewer);
+        if (scrollViewer)
+        {
+            if (SharedHelpers::IsIsLoadedAvailable() && scrollViewer.IsLoaded())
+            {
+                // This scenario occurs reliably for Terminal in XAML islands
+                OnScrollViewerLoaded(nullptr, nullptr);
+            }
+            else
             {
                 m_scrollViewerLoadedRevoker = scrollViewer.Loaded(winrt::auto_revoke, { this, &TabView::OnScrollViewerLoaded });
             }
-            return scrollViewer;
-        }());
+        }
     }
 }
 
diff --git a/dev/dll/SharedHelpers.cpp b/dev/dll/SharedHelpers.cpp
index c0954982af..db99dd52d5 100644
--- a/dev/dll/SharedHelpers.cpp
+++ b/dev/dll/SharedHelpers.cpp
@@ -198,6 +198,14 @@ bool SharedHelpers::IsThemeShadowAvailable()
     return s_isThemeShadowAvailable;
 }
 
+bool SharedHelpers::IsIsLoadedAvailable()
+{
+    static bool s_isAvailable =
+        IsRS5OrHigher() ||
+        winrt::ApiInformation::IsPropertyPresent(L"Windows.UI.Xaml.FrameworkElement", L"IsLoaded");
+    return s_isAvailable;
+}
+
 template <uint16_t APIVersion> bool SharedHelpers::IsAPIContractVxAvailable()
 {
     static bool isAPIContractVxAvailableInitialized = false;
diff --git a/dev/inc/SharedHelpers.h b/dev/inc/SharedHelpers.h
index 5b9f3cba55..6b3193fa44 100644
--- a/dev/inc/SharedHelpers.h
+++ b/dev/inc/SharedHelpers.h
@@ -55,6 +55,8 @@ class SharedHelpers
 
     static bool IsThemeShadowAvailable();
 
+    static bool IsIsLoadedAvailable();
+
     // Actual OS version checks
     static bool IsAPIContractV9Available(); // 19H2
     static bool IsAPIContractV8Available(); // 19H1