From 068159607e57b2a26aa9f3504ea3ec7841312bfa Mon Sep 17 00:00:00 2001
From: Mike Griese <migrie@microsoft.com>
Date: Mon, 22 May 2023 11:00:44 -0500
Subject: [PATCH] Leak the window when it closes on Windows 10 (#15397)

Re: #15384

Basically, when we close a `DesktopWindowXamlSource`, it calls to `Windows_UI_Xaml!DirectUI::MetadataAPI::Reset`, which resets the XAML metadata provider _for the process_. So, closing one DWXS on one thread will force an A/V next time another thread tries to do something like... display a tooltip. Not immediately, but surely soon enough.

This was fixed in Windows 11 by os.2020!5837001. That wasn't backported to Windows 10.

This will cause a ~15MB memory leak PER WINDOW. OBVIOUSLY, this is bad, but it's less bad than crashing.

We're gonna keep using #15384 for other ideas here too.

(cherry picked from commit c589784b54d46187289651fa6c04c49fe05826aa)
Service-Card-Id: 89283538
Service-Version: 1.18
---
 src/cascadia/WindowsTerminal/IslandWindow.cpp | 40 +++++++++++++++++++
 1 file changed, 40 insertions(+)

diff --git a/src/cascadia/WindowsTerminal/IslandWindow.cpp b/src/cascadia/WindowsTerminal/IslandWindow.cpp
index 36b2243f5ed..82f28078f85 100644
--- a/src/cascadia/WindowsTerminal/IslandWindow.cpp
+++ b/src/cascadia/WindowsTerminal/IslandWindow.cpp
@@ -42,6 +42,46 @@ IslandWindow::~IslandWindow()
 
 void IslandWindow::Close()
 {
+    static const bool isWindows11 = []() {
+        OSVERSIONINFOEXW osver{};
+        osver.dwOSVersionInfoSize = sizeof(osver);
+        osver.dwBuildNumber = 22000;
+
+        DWORDLONG dwlConditionMask = 0;
+        VER_SET_CONDITION(dwlConditionMask, VER_BUILDNUMBER, VER_GREATER_EQUAL);
+
+        if (VerifyVersionInfoW(&osver, VER_BUILDNUMBER, dwlConditionMask) != FALSE)
+        {
+            return true;
+        }
+        return false;
+    }();
+
+    if (!isWindows11)
+    {
+        // BODGY
+        //  ____   ____  _____   _______     __
+        // |  _ \ / __ \|  __ \ / ____\ \   / /
+        // | |_) | |  | | |  | | |  __ \ \_/ /
+        // |  _ <| |  | | |  | | | |_ | \   /
+        // | |_) | |__| | |__| | |__| |  | |
+        // |____/ \____/|_____/ \_____|  |_|
+        //
+        // There's a bug in Windows 10 where closing a DesktopWindowXamlSource
+        // on any thread will free an internal static resource that's used by
+        // XAML for the entire process. This would result in closing window
+        // essentially causing the entire app to crash.
+        //
+        // To avoid this, leak the XAML island. We only need to leak this on
+        // Windows 10, since the bug is fixed in Windows 11.
+        //
+        // See GH #15384, MSFT:32109540
+        auto a{ _source };
+        winrt::detach_abi(_source);
+
+        // </BODGY>
+    }
+
     if (_source)
     {
         _source.Close();