Allow unsetting target technology

Yafc.Model/Model/Project.cs

@@ -194,6 +194,7 @@ public ProjectPreferences(Project owner) : base(owner) { }
         public int inserterCapacity { get; set; } = 1;
         public HashSet<FactorioObject> sourceResources { get; } = new HashSet<FactorioObject>();
         public HashSet<FactorioObject> favorites { get; } = new HashSet<FactorioObject>();
+        /// <summary> Target technology for cost analysis - required item counts are estimated for researching this. If null, the is to research all finite technologies. </summary>
         public Technology targetTechnology { get; set; }
 
         protected internal override void AfterDeserialize() {

Yafc/Widgets/ImmediateWidgets.cs

@@ -207,6 +207,7 @@ public static void ShowPrecisionValueTooltip(ImGui gui, float amount, UnitOfMeas
         /// <summary>Shows a dropdown containing the (partial) <paramref name="list"/> of elements, with an action for when an element is selected.</summary>
         /// <param name="count">Maximum number of elements in the list. If there are more another popup can be opened by the user to show the full list.</param>
         /// <param name="width">Width of the popup. Make sure the header text fits!</param>
+        /// <param name="allowNone">Whether to show a "Clear" option which sets the value to <c>null</c>.</param>
         public static void BuildObjectSelectDropDown<T>(this ImGui gui, ICollection<T> list, IComparer<T> ordering, Action<T> select, string header, float width = 20f, int count = 6, bool multiple = false, Predicate<T> checkMark = null, bool allowNone = false, Func<T, string> extra = null) where T : FactorioObject {
             gui.ShowDropDown(imGui => imGui.BuildInlineObjectListAndButton(list, ordering, select, header, count, multiple, checkMark, allowNone, extra), width);
         }

Yafc/Windows/PreferencesScreen.cs

@@ -71,7 +71,7 @@ public override void Build(ImGui gui) {
             ChoiceObject(gui, "Target technology for cost analysis: ", Database.technologies.all, prefs.targetTechnology, x => {
                 prefs.RecordUndo().targetTechnology = x;
                 gui.Rebuild();
-            }, width: 25f);
+            }, width: 25f, allowNone: true);
 
             if (gui.BuildButton("Done")) {
                 Close();
@@ -89,11 +89,12 @@ public override void Build(ImGui gui) {
         /// <summary>Add a GUI element that opens a popup to allow the user to choose from the <paramref name="list"/>, which triggers <paramref name="select"/>.</summary>
         /// <param name="text">Label to show.</param>
         /// <param name="width">Width of the popup. Make sure it is wide enough to fit text!</param>
-        private void ChoiceObject<T>(ImGui gui, string text, T[] list, T current, Action<T> select, float width = 20f) where T : FactorioObject {
+        /// <param name="allowNone">Whether to show a "Clear" option which sets the value to <c>null</c>.</param>
+        private void ChoiceObject<T>(ImGui gui, string text, T[] list, T current, Action<T> select, float width = 20f, bool allowNone = false) where T : FactorioObject {
             using (gui.EnterRow()) {
                 gui.BuildText(text, topOffset: 0.5f);
                 if (gui.BuildFactorioObjectButtonWithText(current)) {
-                    gui.BuildObjectSelectDropDown(list, DataUtils.DefaultOrdering, select, text, width: width);
+                    gui.BuildObjectSelectDropDown(list, DataUtils.DefaultOrdering, select, text, width: width, allowNone: allowNone);
                 }
             }
         }