From e9a1be481fb0c550a139400443192a0d45a7c398 Mon Sep 17 00:00:00 2001
From: Wojtek Figat <wojtek@figat.pl>
Date: Mon, 20 Nov 2023 11:03:49 +0100
Subject: [PATCH] Add short delay before auto-selecting editor tab on drag over
 header

#1934
---
 Source/Editor/GUI/Docking/DockPanelProxy.cs | 37 +++++++++++++--------
 1 file changed, 23 insertions(+), 14 deletions(-)

diff --git a/Source/Editor/GUI/Docking/DockPanelProxy.cs b/Source/Editor/GUI/Docking/DockPanelProxy.cs
index 15ff2cad0..e6e57de8e 100644
--- a/Source/Editor/GUI/Docking/DockPanelProxy.cs
+++ b/Source/Editor/GUI/Docking/DockPanelProxy.cs
@@ -13,6 +13,7 @@ namespace FlaxEditor.GUI.Docking
     public class DockPanelProxy : ContainerControl
     {
         private DockPanel _panel;
+        private double _dragEnterTime = -1;
 
         /// <summary>
         /// The is mouse down flag (left button).
@@ -256,8 +257,8 @@ namespace FlaxEditor.GUI.Docking
                     else
                     {
                         tabColor = style.BackgroundHighlighted;
-                        Render2D.DrawLine(tabRect.BottomLeft - new Float2(0 , 1), tabRect.UpperLeft, tabColor);
-                        Render2D.DrawLine(tabRect.BottomRight - new Float2(0 , 1), tabRect.UpperRight, tabColor);
+                        Render2D.DrawLine(tabRect.BottomLeft - new Float2(0, 1), tabRect.UpperLeft, tabColor);
+                        Render2D.DrawLine(tabRect.BottomRight - new Float2(0, 1), tabRect.UpperRight, tabColor);
                     }
 
                     if (tab.Icon.IsValid)
@@ -477,11 +478,7 @@ namespace FlaxEditor.GUI.Docking
             var result = base.OnDragEnter(ref location, data);
             if (result != DragDropEffect.None)
                 return result;
-
-            if (TrySelectTabUnderLocation(ref location))
-                return DragDropEffect.Move;
-
-            return DragDropEffect.None;
+            return TrySelectTabUnderLocation(ref location);
         }
 
         /// <inheritdoc />
@@ -490,11 +487,15 @@ namespace FlaxEditor.GUI.Docking
             var result = base.OnDragMove(ref location, data);
             if (result != DragDropEffect.None)
                 return result;
+            return TrySelectTabUnderLocation(ref location);
+        }
 
-            if (TrySelectTabUnderLocation(ref location))
-                return DragDropEffect.Move;
+        /// <inheritdoc />
+        public override void OnDragLeave()
+        {
+            _dragEnterTime = -1;
 
-            return DragDropEffect.None;
+            base.OnDragLeave();
         }
 
         /// <inheritdoc />
@@ -503,17 +504,25 @@ namespace FlaxEditor.GUI.Docking
             rect = new Rectangle(0, DockPanel.DefaultHeaderHeight, Width, Height - DockPanel.DefaultHeaderHeight);
         }
 
-        private bool TrySelectTabUnderLocation(ref Float2 location)
+        private DragDropEffect TrySelectTabUnderLocation(ref Float2 location)
         {
             var tab = GetTabAtPos(location, out _);
             if (tab != null)
             {
+                // Auto-select tab only if drag takes some time
+                var time = Platform.TimeSeconds;
+                if (_dragEnterTime < 0)
+                    _dragEnterTime = time;
+                if (time - _dragEnterTime < 0.3f)
+                    return DragDropEffect.Link;
+                _dragEnterTime = -1;
+
                 _panel.SelectTab(tab);
                 Update(0); // Fake update
-                return true;
+                return DragDropEffect.Move;
             }
-
-            return false;
+            _dragEnterTime = -1;
+            return DragDropEffect.None;
         }
 
         private void ShowContextMenu(DockWindow tab, ref Float2 location)