From c41e078e85f6b00527ffab5ca0a4e9cc74504bbf Mon Sep 17 00:00:00 2001
From: Don-Vito <khvitaly@gmail.com>
Date: Wed, 18 Nov 2020 23:31:37 +0200
Subject: [PATCH] Fix a race condition in pane animation completion that broke
 sizing (#8241)

Fixes a race in pane entrance animation, where the animation
completion routine processes wrong children.

Validated w/ manual testing

Closes #8230
---
 src/cascadia/TerminalApp/Pane.cpp | 51 +++++++++++--------------------
 1 file changed, 18 insertions(+), 33 deletions(-)

diff --git a/src/cascadia/TerminalApp/Pane.cpp b/src/cascadia/TerminalApp/Pane.cpp
index b7d94d87e0..d84995cc65 100644
--- a/src/cascadia/TerminalApp/Pane.cpp
+++ b/src/cascadia/TerminalApp/Pane.cpp
@@ -1169,6 +1169,15 @@ void Pane::_SetupEntranceAnimation()
             childGrid.HorizontalAlignment(isFirstChild ? HorizontalAlignment::Left : HorizontalAlignment::Right);
             control.HorizontalAlignment(HorizontalAlignment::Left);
             control.Width(isFirstChild ? totalSize : size);
+
+            // When the animation is completed, undo the trickiness from before, to
+            // restore the controls to the behavior they'd usually have.
+            animation.Completed([childGrid, control](auto&&, auto&&) {
+                control.Width(NAN);
+                childGrid.Width(NAN);
+                childGrid.HorizontalAlignment(HorizontalAlignment::Stretch);
+                control.HorizontalAlignment(HorizontalAlignment::Stretch);
+            });
         }
         else
         {
@@ -1178,43 +1187,19 @@ void Pane::_SetupEntranceAnimation()
             childGrid.VerticalAlignment(isFirstChild ? VerticalAlignment::Top : VerticalAlignment::Bottom);
             control.VerticalAlignment(VerticalAlignment::Top);
             control.Height(isFirstChild ? totalSize : size);
+
+            // When the animation is completed, undo the trickiness from before, to
+            // restore the controls to the behavior they'd usually have.
+            animation.Completed([childGrid, control](auto&&, auto&&) {
+                control.Height(NAN);
+                childGrid.Height(NAN);
+                childGrid.VerticalAlignment(VerticalAlignment::Stretch);
+                control.VerticalAlignment(VerticalAlignment::Stretch);
+            });
         }
 
         // Start the animation.
         s.Begin();
-
-        std::weak_ptr<Pane> weakThis{ shared_from_this() };
-        // When the animation is completed, undo the trickiness from before, to
-        // restore the controls to the behavior they'd usually have.
-        animation.Completed([weakThis, isFirstChild, splitWidth](auto&&, auto&&) {
-            if (auto pane{ weakThis.lock() })
-            {
-                auto child = isFirstChild ? pane->_firstChild : pane->_secondChild;
-
-                // ensure the child was not release in meanwhile
-                if (child)
-                {
-                    auto childGrid = child->_root;
-                    if (auto control = child->_control)
-                    {
-                        if (splitWidth)
-                        {
-                            control.Width(NAN);
-                            childGrid.Width(NAN);
-                            childGrid.HorizontalAlignment(HorizontalAlignment::Stretch);
-                            control.HorizontalAlignment(HorizontalAlignment::Stretch);
-                        }
-                        else
-                        {
-                            control.Height(NAN);
-                            childGrid.Height(NAN);
-                            childGrid.VerticalAlignment(VerticalAlignment::Stretch);
-                            control.VerticalAlignment(VerticalAlignment::Stretch);
-                        }
-                    }
-                }
-            }
-        });
     };
 
     // TODO: GH#7365 - animating the first child right now doesn't _really_ do