further panel performance improvements

CHANGELOG.md

@@ -35,6 +35,7 @@ Additions
 Improvements
 - Allow scrolling panels to contain other scrolling panels
 - Allow dropdowns to have scrolling panels
+- Improved Panel performance when adding and removing a lot of children
 
 Fixes
 - Fixed panels updating their relevant children too much when the scroll bar is hidden

MLEM.Ui/Elements/Panel.cs

@@ -245,12 +245,11 @@ namespace MLEM.Ui.Elements {
         /// <inheritdoc />
         protected override void OnChildAreaDirty(Element child, bool grandchild) {
             base.OnChildAreaDirty(child, grandchild);
+            if (grandchild && !this.AreaDirty) {
                 // we only need to scroll when a grandchild changes, since all of our children are forced
                 // to be auto-anchored and so will automatically propagate their changes up to us
-            if (grandchild) {
                 this.ScrollChildren();
                 // we also need to re-setup here in case the child is involved in a special GetTotalCoveredArea
-                if (!this.AreaDirty)
                 this.ScrollSetup();
             }
         }
@@ -355,16 +354,22 @@ namespace MLEM.Ui.Elements {
         }
 
         private void ScrollChildren() {
-            this.scrolledChildren.RemoveWhere(c => !c.GetParentTree().Contains(this));
             if (!this.scrollOverflow)
                 return;
+
+            var currentChildren = new HashSet<Element>();
+            // scroll all our children (and cache newly added ones)
             // we ignore false grandchildren so that the children of the scroll bar stay in place
             foreach (var child in this.GetChildren(c => c != this.ScrollBar, true, true)) {
                 // if a child was newly added later, the last scroll offset was never applied
                 if (this.scrolledChildren.Add(child))
                     child.ScrollOffset.Y -= this.lastScrollOffset;
                 child.ScrollOffset.Y += (this.lastScrollOffset - this.ScrollBar.CurrentValue);
+                currentChildren.Add(child);
             }
+            // remove cached scrolled children that aren't our children anymore
+            this.scrolledChildren.IntersectWith(currentChildren);
+
             this.lastScrollOffset = this.ScrollBar.CurrentValue;
             this.relevantChildrenDirty = true;
         }

MLEM.Ui/Elements/Paragraph.cs

@@ -232,7 +232,7 @@ namespace MLEM.Ui.Elements {
         private void SetTextDirty() {
             this.tokenizedText = null;
             // only set our area dirty if our size changed as a result of this action
-            if (!this.AreaDirty && !this.CalcActualSize(this.ParentArea).Equals(this.DisplayArea.Size, Element.Epsilon))
+            if (!this.AreaDirty && (this.System == null || !this.CalcActualSize(this.ParentArea).Equals(this.DisplayArea.Size, Element.Epsilon)))
                 this.SetAreaDirty();
         }