Cleanup code and fix layout after option toggle #4219

Source/Engine/UI/GUI/Panels/HorizontalPanel.cs

@@ -45,9 +45,13 @@ namespace FlaxEngine.GUI
             float maxHeight = h;
             bool hasAnyLeft = false, hasAnyRight = false;
 
-            float totalGaps = (_children.Count - 1) * Spacing;
-            float availableWidth = Width - totalGaps - LeftMargin - RightMargin;
-            float itemWidth = availableWidth / _children.Count;
+            float itemWidth = 0;
+            if (_children.Count > 0)
+            {
+                float totalGaps = (_children.Count - 1) * Spacing;
+                float availableWidth = Width - totalGaps - _margin.Width;
+                itemWidth = availableWidth / _children.Count;
+            }
 
             for (int i = 0; i < _children.Count; i++)
             {
@@ -70,9 +74,9 @@ namespace FlaxEngine.GUI
                     }
                     maxHeight = Mathf.Max(maxHeight, ch);
 
-                    if (ExpandChildren)
+                    if (ExpandChildSize)
                     {
-                        c.Width = itemWidth;                       
+                        c.Width = itemWidth;
                     }
                 }
             }

Source/Engine/UI/GUI/Panels/PanelWithMargins.cs

@@ -36,6 +36,7 @@ namespace FlaxEngine.GUI
         protected TextAlignment _alignment = TextAlignment.Near;
 
         private bool _controlChildSize = true;
+        private bool _expandChildSize = false;
 
         /// <summary>
         /// Gets or sets the left margin.
@@ -174,10 +175,21 @@ namespace FlaxEngine.GUI
         }
 
         /// <summary>
-        /// Gets or sets the value indicating whenever the panel can resize children controls (eg. auto-fit width/height).
+        /// If checked, the panel will expand all children in the relevant direction with even spacing and size (horizontally for Horizontal Panel, vertically for Vertical Panel).
         /// </summary>
-        [EditorOrder(36), DefaultValue(false), Tooltip("If checked, the panel will expand all children in the relevant direction with even spacing and size. (Horizontally for Horizontal Panel, Vertically for Vertical Panel).")]
-        public bool ExpandChildren { get; set; } = false;
+        [EditorOrder(36), DefaultValue(false)]
+        public bool ExpandChildSize
+        {
+            get => _expandChildSize;
+            set
+            {
+                if (_expandChildSize != value)
+                {
+                    _expandChildSize = value;
+                    PerformLayout();
+                }
+            }
+        }
 
         /// <summary>
         /// Gets or sets the panel area margin.

Source/Engine/UI/GUI/Panels/VerticalPanel.cs

@@ -1,7 +1,5 @@
 // Copyright (c) Wojciech Figat. All rights reserved.
 
-using System.Globalization;
-
 namespace FlaxEngine.GUI
 {
     /// <summary>
@@ -47,9 +45,13 @@ namespace FlaxEngine.GUI
             float maxWidth = w;
             bool hasAnyTop = false, hasAnyBottom = false;
 
-            float totalGaps = (_children.Count - 1) * Spacing;
-            float availableHeight = Height - totalGaps - TopMargin - BottomMargin;
-            float itemHeight = availableHeight / _children.Count;
+            float itemHeight = 0;
+            if (_children.Count > 0)
+            {
+                float totalGaps = (_children.Count - 1) * Spacing;
+                float availableHeight = Height - totalGaps - _margin.Height;
+                itemHeight = availableHeight / _children.Count;
+            }
 
             for (int i = 0; i < _children.Count; i++)
             {
@@ -72,9 +74,9 @@ namespace FlaxEngine.GUI
                     }
                     maxWidth = Mathf.Max(maxWidth, cw);
 
-                    if (ExpandChildren)
+                    if (ExpandChildSize)
                     {
-                        c.Height = itemHeight;                       
+                        c.Height = itemHeight;
                     }
                 }
             }