[nostalgia] Split PaletteEditor into Imgui and general files, other cleanup

src/nostalgia/studio/lib/editor.hpp

@@ -11,12 +11,17 @@
 
 #include "nostalgiastudio_export.h"
 
+namespace nostalgia {
+class StudioUI;
+}
+
 namespace nostalgia::studio {
 
 class NOSTALGIASTUDIO_EXPORT Editor: public Widget {
 
+	friend StudioUI;
+
 	private:
-		UndoStack m_cmdStack;
 		bool m_unsavedChanges = false;
 		bool m_exportable = false;
 		bool m_cutEnabled = false;
@@ -43,20 +48,12 @@ class NOSTALGIASTUDIO_EXPORT Editor: public Widget {
 
 		virtual void exportFile();
 
-		/**
-		 * Returns the undo stack holding changes to the item being edited.
-		 */
-		[[nodiscard]]
-		virtual UndoStack *undoStack() noexcept {
-			return nullptr;
-		}
-
 		void close();
 
 		/**
 		 * Save changes to item being edited.
 		 */
-		void save();
+		void save() noexcept;
 
 		/**
 		 * Sets indication of item being edited has unsaved changes. Also emits
@@ -91,7 +88,15 @@ class NOSTALGIASTUDIO_EXPORT Editor: public Widget {
 		/**
 		 * Save changes to item being edited.
 		 */
-		virtual void saveItem();
+		virtual ox::Error saveItem() noexcept;
+
+		/**
+		 * Returns the undo stack holding changes to the item being edited.
+		 */
+		[[nodiscard]]
+		virtual UndoStack *undoStack() noexcept {
+			return nullptr;
+		}
 
 	// signals
 	public: