explicitly disallow auto-sizing incompatibilities to make debugging easier

MLEM.Ui/Elements/Element.cs

@@ -626,30 +626,37 @@ namespace MLEM.Ui.Elements {
                 if (this.SetWidthBasedOnChildren || this.SetHeightBasedOnChildren) {
                     Element foundChild = null;
                     var autoSize = this.UnscrolledArea.Size;
+                    
                     if (this.SetHeightBasedOnChildren) {
                         var lowest = this.GetLowestChild(e => !e.IsHidden);
                         if (lowest != null) {
                             autoSize.Y = lowest.UnscrolledArea.Bottom - pos.Y + this.ScaledChildPadding.Bottom;
                             foundChild = lowest;
                         } else {
+                            if (this.Children.Count > 0)
+                                throw new InvalidOperationException($"{this} with root {this.Root.Name} sets its height based on children but it only has children anchored too low ({string.Join(", ", this.Children.Select(c => c.Anchor))})");
                             autoSize.Y = 0;
                         }
                     }
+                    
                     if (this.SetWidthBasedOnChildren) {
                         var rightmost = this.GetRightmostChild(e => !e.IsHidden);
                         if (rightmost != null) {
                             autoSize.X = rightmost.UnscrolledArea.Right - pos.X + this.ScaledChildPadding.Right;
                             foundChild = rightmost;
                         } else {
+                            if (this.Children.Count > 0)
+                                throw new InvalidOperationException($"{this} with root {this.Root.Name} sets its width based on children but it only has children anchored too far right ({string.Join(", ", this.Children.Select(c => c.Anchor))})");
                             autoSize.X = 0;
                         }
                     }
+                    
                     if (this.TreatSizeAsMinimum)
                         autoSize = Vector2.Max(autoSize, actualSize);
                     if (!autoSize.Equals(this.UnscrolledArea.Size, 0.01F)) {
                         recursion++;
                         if (recursion >= 16) {
-                            throw new ArithmeticException($"The area of {this} with root {this.Root?.Name} has recursively updated too often. Does its child {foundChild} contain any conflicting auto-sizing settings?");
+                            throw new ArithmeticException($"The area of {this} with root {this.Root.Name} has recursively updated too often. Does its child {foundChild} contain any conflicting auto-sizing settings?");
                         } else {
                             UpdateDisplayArea(autoSize);
                         }

Tests/UiTests.cs

@@ -31,6 +31,11 @@ namespace Tests {
             invalidPanel.AddChild(new Paragraph(Anchor.AutoRight, 1, "This is some test text!", true));
             invalidPanel.AddChild(new VerticalSpace(1));
             Assert.Throws<ArithmeticException>(() => this.AddAndUpdate(invalidPanel));
+
+            invalidPanel = new Panel(Anchor.Center, Vector2.Zero, Vector2.Zero, true);
+            invalidPanel.AddChild(new Group(Anchor.CenterRight, new Vector2(10), false));
+            invalidPanel.AddChild(new Group(Anchor.BottomLeft, new Vector2(10), false));
+            Assert.Throws<InvalidOperationException>(() => this.AddAndUpdate(invalidPanel));
         }
 
         [Test]