Add support for AssetPreview to use debug drawing if needed

Source/Editor/Viewport/Previews/AssetPreview.cs

@@ -1,5 +1,7 @@
 // Copyright (c) 2012-2021 Wojciech Figat. All rights reserved.
 
+using System;
+using FlaxEditor.Gizmo;
 using FlaxEditor.GUI.ContextMenu;
 using FlaxEditor.Viewport.Cameras;
 using FlaxEngine;
@@ -11,9 +13,13 @@ namespace FlaxEditor.Viewport.Previews
     /// Generic asset preview editor viewport base class.
     /// </summary>
     /// <seealso cref="FlaxEditor.Viewport.EditorViewport" />
-    public abstract class AssetPreview : EditorViewport
+    public abstract class AssetPreview : EditorViewport, IEditorPrimitivesOwner
     {
         private ContextMenuButton _showDefaultSceneButton;
+        private IntPtr _debugDrawContext;
+        private bool _debugDrawEnable;
+        private bool _editorPrimitivesEnable;
+        private EditorPrimitives _editorPrimitives;
 
         /// <summary>
         /// The preview light. Allows to modify rendering settings.
@@ -61,6 +67,56 @@ namespace FlaxEditor.Viewport.Previews
             }
         }
 
+        /// <summary>
+        /// Gets or sets a value indicating whether draw <see cref="DebugDraw"/> shapes.
+        /// </summary>
+        public bool ShowDebugDraw
+        {
+            get => _debugDrawEnable;
+            set
+            {
+                if (_debugDrawEnable == value)
+                    return;
+                _debugDrawEnable = value;
+                if (_debugDrawContext == IntPtr.Zero)
+                {
+                    _debugDrawContext = DebugDraw.AllocateContext();
+                    var view = Task.View;
+                    view.Flags |= ViewFlags.DebugDraw;
+                    Task.View = view;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets or sets a value indicating whether draw <see cref="DebugDraw"/> shapes and other editor primitives such as gizmos.
+        /// </summary>
+        public bool ShowEditorPrimitives
+        {
+            get => _editorPrimitivesEnable;
+            set
+            {
+                if (_editorPrimitivesEnable == value)
+                    return;
+                _editorPrimitivesEnable = value;
+                if (_editorPrimitives == null)
+                {
+                    _editorPrimitives = Object.New<EditorPrimitives>();
+                    _editorPrimitives.Viewport = this;
+                    Task.CustomPostFx.Add(_editorPrimitives);
+                    Task.PostRender += OnPostRender;
+                    var view = Task.View;
+                    view.Flags |= ViewFlags.CustomPostProcess;
+                    Task.View = view;
+                }
+            }
+        }
+
+        /// <summary>
+        /// Gets the editor primitives renderer. Valid only if <see cref="ShowEditorPrimitives"/> is true.
+        /// </summary>
+        public EditorPrimitives EditorPrimitives => _editorPrimitives;
+
         /// <summary>
         /// Initializes a new instance of the <see cref="AssetPreview"/> class.
         /// </summary>
@@ -114,7 +170,7 @@ namespace FlaxEditor.Viewport.Previews
                 SunPower = 9.0f
             };
             //
-            SkyLight = new SkyLight()
+            SkyLight = new SkyLight
             {
                 Mode = SkyLight.Modes.CustomTexture,
                 Brightness = 2.1f,
@@ -135,20 +191,58 @@ namespace FlaxEditor.Viewport.Previews
             Task.AddCustomActor(PostFxVolume);
         }
 
+        private void OnPostRender(GPUContext context, RenderContext renderContext)
+        {
+            if (renderContext.View.Mode != ViewMode.Default && _editorPrimitives && _editorPrimitives.CanRender)
+            {
+                // Render editor primitives, gizmo and debug shapes in debug view modes
+                // Note: can use Output buffer as both input and output because EditorPrimitives is using a intermediate buffers
+                _editorPrimitives.Render(context, ref renderContext, renderContext.Task.Output, renderContext.Task.Output);
+            }
+        }
+
+        /// <summary>
+        /// Called when drawing debug shapes with <see cref="DebugDraw"/> for this viewport.
+        /// </summary>
+        /// <param name="context">The GPU context.</param>
+        /// <param name="renderContext">The render context.</param>
+        protected virtual void OnDebugDraw(GPUContext context, ref RenderContext renderContext)
+        {
+        }
+
         /// <inheritdoc />
         public override bool HasLoadedAssets => base.HasLoadedAssets && Sky.HasContentLoaded && EnvProbe.Probe.IsLoaded && PostFxVolume.HasContentLoaded;
 
         /// <inheritdoc />
         public override void OnDestroy()
         {
-            // Ensure to cleanup created actor objects
             Object.Destroy(ref PreviewLight);
             Object.Destroy(ref EnvProbe);
             Object.Destroy(ref Sky);
             Object.Destroy(ref SkyLight);
             Object.Destroy(ref PostFxVolume);
+            Object.Destroy(ref _editorPrimitives);
+            if (_debugDrawContext != IntPtr.Zero)
+            {
+                DebugDraw.FreeContext(_debugDrawContext);
+                _debugDrawContext = IntPtr.Zero;
+            }
 
             base.OnDestroy();
         }
+
+        /// <inheritdoc />
+        public virtual void DrawEditorPrimitives(GPUContext context, ref RenderContext renderContext, GPUTexture target, GPUTexture targetDepth)
+        {
+            // Draw selected objects debug shapes and visuals
+            if (ShowDebugDraw && (renderContext.View.Flags & ViewFlags.DebugDraw) == ViewFlags.DebugDraw)
+            {
+                DebugDraw.SetContext(_debugDrawContext);
+                DebugDraw.UpdateContext(_debugDrawContext, 1.0f / Mathf.Max(Engine.FramesPerSecond, 1));
+                OnDebugDraw(context, ref renderContext);
+                DebugDraw.Draw(ref renderContext, target.View(), targetDepth.View(), true);
+                DebugDraw.SetContext(IntPtr.Zero);
+            }
+        }
     }
 }