From 84204aed4655232feb08f92f9374aad5f3c0b1de Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Simon=20L=C3=BCbe=C3=9F?= <simon.luebess@gmail.com>
Date: Sun, 17 Mar 2024 20:10:35 +0100
Subject: [PATCH] No longer crash when selected entity disappears

---
 .../src/EditWindows/ComponentEditWindow.bf    |  6 ++-
 .../src/EditWindows/EditorViewportWindow.bf   |  2 +-
 .../src/EditWindows/EntityHierarchyWindow.bf  | 45 ++++++++++++++-----
 3 files changed, 39 insertions(+), 14 deletions(-)

diff --git a/GlitchyEditor/src/EditWindows/ComponentEditWindow.bf b/GlitchyEditor/src/EditWindows/ComponentEditWindow.bf
index cd2d448..583a7da 100644
--- a/GlitchyEditor/src/EditWindows/ComponentEditWindow.bf
+++ b/GlitchyEditor/src/EditWindows/ComponentEditWindow.bf
@@ -49,8 +49,10 @@ namespace GlitchyEditor.EditWindows
 
 			if (_entityHierarchyWindow.SelectionSize == 1)
 			{
-				Entity entity = _entityHierarchyWindow.GetSelectedEntity(0);
-				ShowComponents(entity);
+				Result<Entity> entityResult = _entityHierarchyWindow.GetSelectedEntity(0);
+
+				if (entityResult case .Ok(let selectedEntity))
+					ShowComponents(selectedEntity);
 			}
 			else
 			{
diff --git a/GlitchyEditor/src/EditWindows/EditorViewportWindow.bf b/GlitchyEditor/src/EditWindows/EditorViewportWindow.bf
index d316a34..fe5cbc0 100644
--- a/GlitchyEditor/src/EditWindows/EditorViewportWindow.bf
+++ b/GlitchyEditor/src/EditWindows/EditorViewportWindow.bf
@@ -326,7 +326,7 @@ namespace GlitchyEditor.EditWindows
 			if(_editor.EntityHierarchyWindow.SelectionSize == 0)
 				return false;
 
-			Entity entity = _editor.EntityHierarchyWindow.GetSelectedEntity(-1);
+			Entity entity = TrySilent!(_editor.EntityHierarchyWindow.GetSelectedEntity(-1));
 
 			var transformCmp = entity.GetComponent<TransformComponent>();
 
diff --git a/GlitchyEditor/src/EditWindows/EntityHierarchyWindow.bf b/GlitchyEditor/src/EditWindows/EntityHierarchyWindow.bf
index 80f9568..4914a1b 100644
--- a/GlitchyEditor/src/EditWindows/EntityHierarchyWindow.bf
+++ b/GlitchyEditor/src/EditWindows/EntityHierarchyWindow.bf
@@ -37,7 +37,7 @@ namespace GlitchyEditor.EditWindows
 		public int SelectionSize => _selectedEntityIds.Count;
 
 		/// Returns the Entity at the given index or null if it doesn't exist.
-		public Entity GetSelectedEntity(int index)
+		public Result<Entity> GetSelectedEntity(int index)
 		{
 			var index;
 
@@ -50,10 +50,14 @@ namespace GlitchyEditor.EditWindows
 
 			if (selectedEntity case .Ok(let entity))
 				return entity;
+			else
+			{
+				// Entity doesn't exist. This can have many reasons, but it is safe to assume, that it existed at some point and probably got deleted.
+				// Thus we just remove it from the selection.
+				_selectedEntityIds.RemoveAt(index);
 
-			// TODO: The entity should always exist in the scene, I'm sure!
-			// If we can assume that, then we can remove the nullable and make everything even easier!
-			Runtime.FatalError(scope $"No entity exists with selected id \"{id}\".");
+				return .Err;
+			}
 		}
 
 		public void HighlightEntity(Entity e)
@@ -188,7 +192,12 @@ namespace GlitchyEditor.EditWindows
 
 			for (int i < SelectionSize)
 			{
-				Entity entity = GetSelectedEntity(i);
+				Result<Entity> entityResult = GetSelectedEntity(i);
+
+				if (entityResult case .Err)
+					continue;
+
+				Entity entity = entityResult;
 
 				var transformComponent = entity.GetComponent<TransformComponent>();
 
@@ -275,7 +284,7 @@ namespace GlitchyEditor.EditWindows
 				return;
 			}
 
-			let commonParent = GetSelectedEntity(0).GetComponent<TransformComponent>();
+			let commonParent = TrySilent!(GetSelectedEntity(0)).GetComponent<TransformComponent>();
 
 			let newEntity = _scene.CreateEntity();
 
@@ -290,7 +299,12 @@ namespace GlitchyEditor.EditWindows
 			// new entity is parent of all selected entities.
 			for (int i < SelectionSize)
 			{
-				let selectedTransform = GetSelectedEntity(i).GetComponent<TransformComponent>();
+				Result<Entity> selectedEntity = GetSelectedEntity(i);
+
+				if (selectedEntity case .Err)
+					continue;
+
+				let selectedTransform = selectedEntity.Value.GetComponent<TransformComponent>();
 				selectedTransform?.Parent = newEntity.Handle;
 			}
 		}
@@ -307,8 +321,13 @@ namespace GlitchyEditor.EditWindows
 							_scene.CreateEntity();
 						else
 						{
-							Entity? parent = GetSelectedEntity(-1).Parent;
-							CreateChild(parent);
+							Result<Entity> selectedEntityResult = GetSelectedEntity(-1);
+
+							if (selectedEntityResult case .Ok(let selectedEntity))
+							{
+								Entity? parent = selectedEntity.Parent;
+								CreateChild(parent);
+							}
 						}
 					}
 
@@ -322,8 +341,12 @@ namespace GlitchyEditor.EditWindows
 				{
 					if(ImGui.MenuItem("Empty Child", null, false, SelectionSize != 0))
 					{
-						Entity selectedEntity = GetSelectedEntity(-1);
-						CreateChild(selectedEntity);
+						Result<Entity> selectedEntityResult = GetSelectedEntity(-1);
+
+						if (selectedEntityResult case .Ok(let selectedEntity))
+						{
+							CreateChild(selectedEntity);
+						}
 					}
 					
 					if(ImGui.IsItemHovered())