From ac8b09e74fd4a852f2e89a0fa5e378b5cb3d2e29 Mon Sep 17 00:00:00 2001
From: Ellpeck <megamaximal@gmail.com>
Date: Wed, 25 Dec 2019 12:15:55 +0100
Subject: [PATCH] improve ui root sorting

---
 MLEM.Ui/Elements/Element.cs |  1 -
 MLEM.Ui/UiSystem.cs         | 46 +++++++++++++++++++------------------
 2 files changed, 24 insertions(+), 23 deletions(-)

diff --git a/MLEM.Ui/Elements/Element.cs b/MLEM.Ui/Elements/Element.cs
index 1de91d7..2e2b75f 100644
--- a/MLEM.Ui/Elements/Element.cs
+++ b/MLEM.Ui/Elements/Element.cs
@@ -180,7 +180,6 @@ namespace MLEM.Ui.Elements {
                 if (this.Root != null)
                     this.Root.OnElementRemoved(e);
             });
-            this.SetSortedChildrenDirty();
             this.SetAreaDirty();
         }
 
diff --git a/MLEM.Ui/UiSystem.cs b/MLEM.Ui/UiSystem.cs
index 67f6ebb..9717d2f 100644
--- a/MLEM.Ui/UiSystem.cs
+++ b/MLEM.Ui/UiSystem.cs
@@ -124,18 +124,10 @@ namespace MLEM.Ui {
         }
 
         public RootElement Add(string name, Element element) {
+            if (this.IndexOf(name) >= 0)
+                return null;
             var root = new RootElement(name, element, this);
-            return !this.Add(root, true) ? null : root;
-        }
-
-        internal bool Add(RootElement root, bool notify, int index = -1) {
-            if (this.IndexOf(root.Name) >= 0)
-                return false;
-            if (index < 0 || index > this.rootElements.Count)
-                index = this.rootElements.Count;
-            this.rootElements.Insert(index, root);
-            if (!notify)
-                return true;
+            this.rootElements.Add(root);
             root.Element.AndChildren(e => {
                 e.Root = root;
                 e.System = this;
@@ -143,20 +135,15 @@ namespace MLEM.Ui {
                 e.SetAreaDirty();
             });
             this.OnRootAdded?.Invoke(root);
-            return true;
+            this.SortRoots();
+            return root;
         }
 
         public void Remove(string name) {
-            this.Remove(name, true);
-        }
-
-        internal void Remove(string name, bool notify) {
             var root = this.Get(name);
             if (root == null)
                 return;
             this.rootElements.Remove(root);
-            if (!notify)
-                return;
             root.SelectElement(null);
             root.Element.AndChildren(e => {
                 e.Root = null;
@@ -176,6 +163,13 @@ namespace MLEM.Ui {
             return this.rootElements.FindIndex(element => element.Name == name);
         }
 
+        internal void SortRoots() {
+            // Normal list sorting isn't stable, but ordering is
+            var sorted = this.rootElements.OrderBy(root => root.Priority).ToArray();
+            this.rootElements.Clear();
+            this.rootElements.AddRange(sorted);
+        }
+
         public IEnumerable<RootElement> GetRootElements() {
             for (var i = this.rootElements.Count - 1; i >= 0; i--)
                 yield return this.rootElements[i];
@@ -205,6 +199,14 @@ namespace MLEM.Ui {
                 this.Element.ForceUpdateArea();
             }
         }
+        private int priority;
+        public int Priority {
+            get => this.priority;
+            set {
+                this.priority = value;
+                this.System.SortRoots();
+            }
+        }
         public float ActualScale => this.System.GlobalScale * this.Scale;
 
         public Matrix Transform = Matrix.Identity;
@@ -243,14 +245,14 @@ namespace MLEM.Ui {
             this.System.OnSelectedElementChanged?.Invoke(element);
         }
 
+        [Obsolete("Use the Priority property for greater control")]
         public void MoveToFront() {
-            this.System.Remove(this.Name, false);
-            this.System.Add(this, false);
+            this.Priority = 10000;
         }
 
+        [Obsolete("Use the Priority property for greater control")]
         public void MoveToBack() {
-            this.System.Remove(this.Name, false);
-            this.System.Add(this, false, 0);
+            this.Priority = -10000;
         }
 
     }