From 19caa5e533a895403752eda0bec9fa5ef336fd57 Mon Sep 17 00:00:00 2001
From: Wojtek Figat <wojtek@figat.pl>
Date: Fri, 7 Aug 2026 07:08:17 +0200
Subject: [PATCH] Fix material drag over highlights to not flicker

---
 .../Editor/Viewport/MainEditorGizmoViewport.cs   |  4 +++-
 Source/Editor/Viewport/PrefabWindowViewport.cs   |  4 +++-
 Source/Editor/Viewport/ViewportDraggingHelper.cs | 16 +++++++++++++---
 Source/Editor/ViewportDebugDrawData.cs           |  2 ++
 4 files changed, 21 insertions(+), 5 deletions(-)

diff --git a/Source/Editor/Viewport/MainEditorGizmoViewport.cs b/Source/Editor/Viewport/MainEditorGizmoViewport.cs
index 51b240202..f457edd29 100644
--- a/Source/Editor/Viewport/MainEditorGizmoViewport.cs
+++ b/Source/Editor/Viewport/MainEditorGizmoViewport.cs
@@ -787,10 +787,12 @@ namespace FlaxEditor.Viewport
         /// <inheritdoc />
         public override DragDropEffect OnDragMove(ref Float2 location, DragData data)
         {
-            DragHandlers.ClearDragEffects();
             var result = base.OnDragMove(ref location, data);
             if (result != DragDropEffect.None)
+            {
+                DragHandlers.ClearDragEffects();
                 return result;
+            }
             return DragHandlers.DragEnter(ref location, data);
         }
 
diff --git a/Source/Editor/Viewport/PrefabWindowViewport.cs b/Source/Editor/Viewport/PrefabWindowViewport.cs
index a599615de..0a3b4b4e5 100644
--- a/Source/Editor/Viewport/PrefabWindowViewport.cs
+++ b/Source/Editor/Viewport/PrefabWindowViewport.cs
@@ -647,10 +647,12 @@ namespace FlaxEditor.Viewport
         /// <inheritdoc />
         public override DragDropEffect OnDragMove(ref Float2 location, DragData data)
         {
-            DragHandlers.ClearDragEffects();
             var result = base.OnDragMove(ref location, data);
             if (result != DragDropEffect.None)
+            {
+                DragHandlers.ClearDragEffects();
                 return result;
+            }
             return DragHandlers.DragEnter(ref location, data);
         }
 
diff --git a/Source/Editor/Viewport/ViewportDraggingHelper.cs b/Source/Editor/Viewport/ViewportDraggingHelper.cs
index 3e6fce6ad..5c68b399a 100644
--- a/Source/Editor/Viewport/ViewportDraggingHelper.cs
+++ b/Source/Editor/Viewport/ViewportDraggingHelper.cs
@@ -65,7 +65,7 @@ namespace FlaxEditor.Viewport
         {
             if (_previewStaticModel)
                 debugDrawData.HighlightModel(_previewStaticModel, _previewModelEntryIndex);
-            if (_previewBrushSurface.Brush != null)
+            if (_previewBrushSurface.Brush)
                 debugDrawData.HighlightBrushSurface(_previewBrushSurface);
         }
 
@@ -120,10 +120,12 @@ namespace FlaxEditor.Viewport
             if (_dragAssets.HasValidDrag && _dragAssets.Objects[0].IsOfType<MaterialBase>())
             {
                 GetHitLocation(ref location, out var hit, out _, out _);
-                ClearDragEffects();
                 var material = FlaxEngine.Content.LoadAsync<MaterialBase>(_dragAssets.Objects[0].ID);
-                if (material.IsDecal)
+                if (material && material.IsDecal)
+                {
+                    ClearDragEffects();
                     return;
+                }
 
                 if (hit is StaticModelNode staticModelNode)
                 {
@@ -135,6 +137,14 @@ namespace FlaxEditor.Viewport
                 {
                     _previewBrushSurface = brushSurfaceNode.Surface;
                 }
+                else
+                {
+                    ClearDragEffects();
+                }
+            }
+            else
+            {
+                ClearDragEffects();
             }
         }
 
diff --git a/Source/Editor/ViewportDebugDrawData.cs b/Source/Editor/ViewportDebugDrawData.cs
index 7b5bee95c..d70ec9cfb 100644
--- a/Source/Editor/ViewportDebugDrawData.cs
+++ b/Source/Editor/ViewportDebugDrawData.cs
@@ -80,6 +80,8 @@ namespace FlaxEditor
         /// <param name="surface">The surface.</param>
         public void HighlightBrushSurface(BrushSurface surface)
         {
+            if (surface.Brush == null)
+                return;
             surface.Brush.GetVertices(surface.Index, out var vertices);
             if (vertices.Length > 0)
             {