From 5f7956a7a3c9dc9fe609b5a10c29cd9339ef6105 Mon Sep 17 00:00:00 2001
From: Ellpeck <me@ellpeck.de>
Date: Wed, 24 Mar 2021 22:01:02 +0100
Subject: [PATCH] properly stop a panel's scroll bar from being removed

---
 MLEM.Ui/Elements/Element.cs |  6 +++---
 MLEM.Ui/Elements/Panel.cs   | 17 +++++++++++++----
 2 files changed, 16 insertions(+), 7 deletions(-)

diff --git a/MLEM.Ui/Elements/Element.cs b/MLEM.Ui/Elements/Element.cs
index 55dcb71..d16f2ca 100644
--- a/MLEM.Ui/Elements/Element.cs
+++ b/MLEM.Ui/Elements/Element.cs
@@ -423,7 +423,7 @@ namespace MLEM.Ui.Elements {
         /// <param name="index">The index to add the child at, or -1 to add it to the end of the <see cref="Children"/> list</param>
         /// <typeparam name="T">The type of child to add</typeparam>
         /// <returns>This element, for chaining</returns>
-        public T AddChild<T>(T element, int index = -1) where T : Element {
+        public virtual T AddChild<T>(T element, int index = -1) where T : Element {
             if (index < 0 || index > this.children.Count)
                 index = this.children.Count;
             this.children.Insert(index, element);
@@ -443,7 +443,7 @@ namespace MLEM.Ui.Elements {
         /// Removes the given child from this element.
         /// </summary>
         /// <param name="element">The child element to remove</param>
-        public void RemoveChild(Element element) {
+        public virtual void RemoveChild(Element element) {
             this.children.Remove(element);
             // set area dirty here so that a dirty call is made
             // upwards to us if the element is auto-positioned
@@ -462,7 +462,7 @@ namespace MLEM.Ui.Elements {
         /// Removes all children from this element that match the given condition.
         /// </summary>
         /// <param name="condition">The condition that determines if a child should be removed</param>
-        public void RemoveChildren(Func<Element, bool> condition = null) {
+        public virtual void RemoveChildren(Func<Element, bool> condition = null) {
             for (var i = this.Children.Count - 1; i >= 0; i--) {
                 var child = this.Children[i];
                 if (condition == null || condition(child)) {
diff --git a/MLEM.Ui/Elements/Panel.cs b/MLEM.Ui/Elements/Panel.cs
index cd93684..b294127 100644
--- a/MLEM.Ui/Elements/Panel.cs
+++ b/MLEM.Ui/Elements/Panel.cs
@@ -108,11 +108,20 @@ namespace MLEM.Ui.Elements {
         /// <inheritdoc />
         public override void ForceUpdateSortedChildren() {
             base.ForceUpdateSortedChildren();
-            if (this.scrollOverflow) {
-                if (this.ScrollBar.Parent != this)
-                    throw new NotSupportedException("A panel that scrolls overflow cannot have its scroll bar removed from its list of children");
+            if (this.scrollOverflow)
                 this.relevantChildrenDirty = true;
-            }
+        }
+
+        /// <inheritdoc />
+        public override void RemoveChild(Element element) {
+            if (element == this.ScrollBar)
+                throw new NotSupportedException("A panel that scrolls overflow cannot have its scroll bar removed from its list of children");
+            base.RemoveChild(element);
+        }
+
+        /// <inheritdoc />
+        public override void RemoveChildren(Func<Element, bool> condition = null) {
+            base.RemoveChildren(e => e != this.ScrollBar && (condition == null || condition(e)));
         }
 
         /// <inheritdoc />