Fixed a stack overflow exception when a panel's scroll bar auto-hiding causes elements to gain height

CHANGELOG.md

@@ -34,6 +34,7 @@ Improvements
 
 Fixes
 - Fixed panels updating their relevant children too much when the scroll bar is hidden
+- Fixed a stack overflow exception when a panel's scroll bar auto-hiding causes elements to gain height
 
 ### MLEM.Data
 Fixes

MLEM.Ui/Elements/Panel.cs

@@ -56,6 +56,7 @@ namespace MLEM.Ui.Elements {
 
         private readonly List<Element> relevantChildren = new List<Element>();
         private readonly HashSet<Element> scrolledChildren = new HashSet<Element>();
+        private readonly float[] scrollBarMaxHistory = new float[3];
         private readonly bool scrollOverflow;
 
         private RenderTarget2D renderTarget;
@@ -110,7 +111,10 @@ namespace MLEM.Ui.Elements {
                         throw new NotSupportedException($"A panel that handles overflow can't contain non-automatic anchors ({child})");
                 }
             }
+
             base.ForceUpdateArea();
+            Array.Clear(this.scrollBarMaxHistory, 0, this.scrollBarMaxHistory.Length);
+
             this.SetScrollBarStyle();
         }
 
@@ -273,9 +277,16 @@ namespace MLEM.Ui.Elements {
             // the max value of the scroll bar is the amount of non-scaled pixels taken up by overflowing components
             var scrollBarMax = Math.Max(0, (childrenHeight - this.ChildPaddedArea.Height) / this.Scale);
             if (!this.ScrollBar.MaxValue.Equals(scrollBarMax, Element.Epsilon)) {
+                // avoid a show/hide oscillation that occurs while updating our area with children that can lose height when the scroll bar is shown (like long paragraphs)
+                if (!this.scrollBarMaxHistory[0].Equals(this.scrollBarMaxHistory[2], Element.Epsilon) || !this.scrollBarMaxHistory[1].Equals(scrollBarMax, Element.Epsilon)) {
+                    this.scrollBarMaxHistory[0] = this.scrollBarMaxHistory[1];
+                    this.scrollBarMaxHistory[1] = this.scrollBarMaxHistory[2];
+                    this.scrollBarMaxHistory[2] = scrollBarMax;
+
                     this.ScrollBar.MaxValue = scrollBarMax;
                     this.relevantChildrenDirty = true;
                 }
+            }
 
             // update child padding based on whether the scroll bar is visible
             var childOffset = this.ScrollBar.IsHidden ? 0 : this.ScrollerSize.Value.X + this.ScrollBarOffset;