Fix 5676ce7a, where returning to the Welcome screen and opening a project again could break panels in the main window.

Yafc/Windows/MilestonesEditor.cs

@@ -5,7 +5,6 @@
 
 namespace Yafc {
     public class MilestonesEditor : PseudoScreen {
-        private static readonly MilestonesEditor Instance = new MilestonesEditor();
         private readonly VirtualScrollList<FactorioObject> milestoneList;
 
         public MilestonesEditor() : base(50) => milestoneList = new VirtualScrollList<FactorioObject>(30f, new Vector2(float.PositiveInfinity, 3f), MilestoneDrawer, MainScreen.Instance.InputSystem);
@@ -15,7 +14,7 @@ public override void Open() {
             milestoneList.data = Project.current.settings.milestones;
         }
 
-        public static void Show() => _ = MainScreen.Instance.ShowPseudoScreen(Instance);
+        public static void Show() => _ = MainScreen.Instance.ShowPseudoScreen(new MilestonesEditor());
 
         private void MilestoneDrawer(ImGui gui, FactorioObject element, int index) {
             using (gui.EnterRow()) {

Yafc/Windows/NeverEnoughItemsPanel.cs

@@ -5,7 +5,7 @@
 
 namespace Yafc {
     public class NeverEnoughItemsPanel : PseudoScreen, IComparer<NeverEnoughItemsPanel.RecipeEntry> {
-        private static readonly NeverEnoughItemsPanel Instance = new NeverEnoughItemsPanel();
+        private static NeverEnoughItemsPanel? Instance;
         private Goods current = null!; // null-forgiving: Set by Show.
         private Goods? changing;
         private float currentFlow;
@@ -71,9 +71,11 @@ private NeverEnoughItemsPanel() : base(76f) {
         /// It is only necessary to call this from screens that could be displayed on top of the NEIE display.
         /// </summary>
         public static void Refresh() {
-            var item = Instance.current;
-            Instance.current = null!; // null-forgiving: We immediately reset this.
-            Instance.SetItem(item);
+            if (Instance != null) {
+                var item = Instance.current;
+                Instance.current = null!; // null-forgiving: We immediately reset this.
+                Instance.SetItem(item);
+            }
         }
 
         private void SetItem(Goods current) {
@@ -384,13 +386,20 @@ public static void Show(Goods goods) {
             // easily handle that since the setting updates happen after the milestones screens are closed.
             Refresh();
 
-            if (Instance.opened) {
+            if (Instance?.opened ?? false) {
                 Instance.changing = goods;
                 return;
             }
+            Instance ??= new();
             Instance.SetItem(goods);
             _ = MainScreen.Instance.ShowPseudoScreen(Instance);
         }
+
+        protected override void Close(bool save = true) {
+            Instance = null;
+            base.Close(save);
+        }
+
         int IComparer<RecipeEntry>.Compare(RecipeEntry x, RecipeEntry y) {
             if (x.entryStatus != y.entryStatus) {
                 return y.entryStatus - x.entryStatus;

Yafc/Windows/PreferencesScreen.cs

@@ -4,8 +4,6 @@
 
 namespace Yafc {
     public class PreferencesScreen : PseudoScreen {
-        private static readonly PreferencesScreen Instance = new PreferencesScreen();
-
         public override void Build(ImGui gui) {
             BuildHeader(gui, "Preferences");
             gui.BuildText("Unit of time:", Font.subheader);
@@ -183,6 +181,6 @@ private void BuildUnitPerTime(ImGui gui, bool fluid, ProjectPreferences preferen
             }
         }
 
-        public static void Show() => _ = MainScreen.Instance.ShowPseudoScreen(Instance);
+        public static void Show() => _ = MainScreen.Instance.ShowPseudoScreen(new PreferencesScreen());
     }
 }

Yafc/Windows/SelectSingleObjectPanel.cs

@@ -8,7 +8,6 @@ namespace Yafc {
     /// Represents a panel that can generate a result by selecting zero or one <see cref="FactorioObject"/>s. (But doesn't have to, if the user selects a close or cancel button.)
     /// </summary>
     public class SelectSingleObjectPanel : SelectObjectPanel<FactorioObject> {
-        private static readonly SelectSingleObjectPanel Instance = new SelectSingleObjectPanel();
         public SelectSingleObjectPanel() : base() { }
 
         /// <summary>
@@ -19,7 +18,7 @@ public SelectSingleObjectPanel() : base() { }
         /// <param name="selectItem">An action to be called for the selected item when the panel is closed.</param>
         /// <param name="ordering">An optional ordering specifying how to sort the displayed items. If <see langword="null"/>, defaults to <see cref="DataUtils.DefaultOrdering"/>.</param>
         public static void Select<T>(IEnumerable<T> list, string header, Action<T> selectItem, IComparer<T>? ordering = null) where T : FactorioObject
-            => Instance.Select(list, header, selectItem!, ordering, (obj, mappedAction) => mappedAction(obj), false); // null-forgiving: selectItem will not be called with null, because allowNone is false.
+            => new SelectSingleObjectPanel().Select(list, header, selectItem!, ordering, (obj, mappedAction) => mappedAction(obj), false); // null-forgiving: selectItem will not be called with null, because allowNone is false.
 
         /// <summary>
         /// Opens a <see cref="SelectSingleObjectPanel"/> to allow the user to select one <see cref="FactorioObject"/>, or to clear the current selection by selecting
@@ -30,7 +29,7 @@ public static void Select<T>(IEnumerable<T> list, string header, Action<T> selec
         /// <param name="selectItem">An action to be called for the selected item when the panel is closed. The parameter will be <see langword="null"/> if the "none" or "clear" option is selected.</param>
         /// <param name="ordering">An optional ordering specifying how to sort the displayed items. If <see langword="null"/>, defaults to <see cref="DataUtils.DefaultOrdering"/>.</param>
         public static void SelectWithNone<T>(IEnumerable<T> list, string header, Action<T?> selectItem, IComparer<T>? ordering = null) where T : FactorioObject
-            => Instance.Select(list, header, selectItem, ordering, (obj, mappedAction) => mappedAction(obj), true);
+            => new SelectSingleObjectPanel().Select(list, header, selectItem, ordering, (obj, mappedAction) => mappedAction(obj), true);
 
         protected override void NonNullElementDrawer(ImGui gui, FactorioObject element, int index) {
             if (gui.BuildFactorioObjectButton(element, 2.5f, MilestoneDisplay.Contained, extendHeader: extendHeader, useScale: true) == Click.Left) {

Yafc/Windows/ShoppingListScreen.cs

@@ -7,8 +7,6 @@
 
 namespace Yafc {
     public class ShoppingListScreen : PseudoScreen {
-        private static readonly ShoppingListScreen Instance = new ShoppingListScreen();
-
         private readonly VirtualScrollList<(FactorioObject, float)> list;
         private float shoppingCost, totalBuildings, totalModules;
         private bool decomposed = false;
@@ -25,9 +23,8 @@ private void ElementDrawer(ImGui gui, (FactorioObject obj, float count) element,
 
         public static void Show(Dictionary<FactorioObject, int> counts) {
             float cost = 0f, buildings = 0f, modules = 0f;
-            Instance.decomposed = false;
-            Instance.list.data = counts.Select(x => (x.Key, Value: (float)x.Value)).OrderByDescending(x => x.Value).ToArray();
-            foreach (var (obj, count) in Instance.list.data) {
+            var data = counts.Select(x => (x.Key, Value: (float)x.Value)).OrderByDescending(x => x.Value).ToArray();
+            foreach ((FactorioObject obj, float count) in data) {
                 if (obj is Entity) {
                     buildings += count;
                 }
@@ -37,10 +34,14 @@ public static void Show(Dictionary<FactorioObject, int> counts) {
 
                 cost += obj.Cost() * count;
             }
-            Instance.shoppingCost = cost;
-            Instance.totalBuildings = buildings;
-            Instance.totalModules = modules;
-            _ = MainScreen.Instance.ShowPseudoScreen(Instance);
+
+            ShoppingListScreen screen = new() {
+                shoppingCost = cost,
+                totalBuildings = buildings,
+                totalModules = modules,
+                list = { data = data }
+            };
+            _ = MainScreen.Instance.ShowPseudoScreen(screen);
         }
 
         public override void Build(ImGui gui) {

Yafc/Windows/WizardPanel.cs

@@ -6,8 +6,6 @@
 
 namespace Yafc {
     public class WizardPanel : PseudoScreen {
-        public static readonly WizardPanel Instance = new WizardPanel();
-
         private readonly List<PageBuilder> pages = [];
         private string? header;
         private Action? finish;
@@ -17,10 +15,9 @@ public class WizardPanel : PseudoScreen {
         public delegate Action WizardBuilder(List<PageBuilder> pages);
 
         public static void Show(string header, WizardBuilder builder) {
-            Instance.pages.Clear();
-            Instance.finish = builder(Instance.pages);
-            Instance.header = header;
-            _ = MainScreen.Instance.ShowPseudoScreen(Instance);
+            WizardPanel panel = new() { header = header };
+            panel.finish = builder(panel.pages);
+            _ = MainScreen.Instance.ShowPseudoScreen(panel);
         }
 
         public override void Open() {

Yafc/Workspace/ProductionTable/ModuleCustomizationScreen.cs

@@ -6,24 +6,24 @@
 
 namespace Yafc {
     public class ModuleCustomizationScreen : PseudoScreen {
-        private static readonly ModuleCustomizationScreen Instance = new ModuleCustomizationScreen();
-
         private RecipeRow? recipe;
         private ProjectModuleTemplate? template;
         private ModuleTemplate? modules;
 
         public static void Show(RecipeRow recipe) {
-            Instance.template = null;
-            Instance.recipe = recipe;
-            Instance.modules = recipe.modules;
-            _ = MainScreen.Instance.ShowPseudoScreen(Instance);
+            ModuleCustomizationScreen screen = new() {
+                recipe = recipe,
+                modules = recipe.modules
+            };
+            _ = MainScreen.Instance.ShowPseudoScreen(screen);
         }
 
         public static void Show(ProjectModuleTemplate template) {
-            Instance.recipe = null;
-            Instance.template = template;
-            Instance.modules = template.template;
-            _ = MainScreen.Instance.ShowPseudoScreen(Instance);
+            ModuleCustomizationScreen screen = new() {
+                template = template,
+                modules = template.template
+            };
+            _ = MainScreen.Instance.ShowPseudoScreen(screen);
         }
 
         public override void Build(ImGui gui) {

Yafc/Workspace/ProductionTable/ModuleTemplateConfiguration.cs

@@ -4,7 +4,6 @@
 
 namespace Yafc {
     public class ModuleTemplateConfiguration : PseudoScreen {
-        private static readonly ModuleTemplateConfiguration Instance = new ModuleTemplateConfiguration();
         private readonly VirtualScrollList<ProjectModuleTemplate> templateList;
         private ProjectModuleTemplate? pageToDelete;
         private string newPageName = "";
@@ -13,8 +12,9 @@ public class ModuleTemplateConfiguration : PseudoScreen {
                 reorder: (from, to) => Project.current.RecordUndo().sharedModuleTemplates.MoveListElementIndex(from, to));
 
         public static void Show() {
-            Instance.RefreshList();
-            _ = MainScreen.Instance.ShowPseudoScreen(Instance);
+            ModuleTemplateConfiguration screen = new();
+            screen.RefreshList();
+            _ = MainScreen.Instance.ShowPseudoScreen(screen);
         }
 
         private void RefreshList() {