redid save file so it's compressed and in xml (which is used for a lot of stuff like this)

src/layout/types.rs

@@ -212,6 +212,7 @@ pub struct WindowSettings {
 }
 
 #[derive(Debug, Clone, PartialEq, Eq, Serialize, Deserialize, Default)]
+#[serde(default)]
 pub struct DungeonLayout {
     pub name: String,
     pub rooms: Vec<Room>,

src/saveandload.rs

@@ -1,13 +1,16 @@
 /*
  * Persistence logic for dungeon state.
  * Handles saving and loading the complete dungeon state
- * (settings and layout data) to and from disk using JSON.
+ * (settings, layout data, and SVGs) to and from compressed XML archives.
  */
 
 use rfd::FileDialog;
 use serde::{Deserialize, Serialize};
 use std::fs;
+use std::io::{Cursor, Read, Write};
 use std::path::PathBuf;
+use zip::write::SimpleFileOptions;
+use zip::{CompressionMethod, ZipArchive, ZipWriter};
 
 use crate::layout::DungeonLayout;
 use crate::ui::UiSettings;
@@ -19,7 +22,66 @@ pub struct DungeonSave {
     pub svgs: Vec<String>,
 }
 
-// Saves dungeon state to a user-selected JSON file.
+const XML_ENTRY_NAME: &str = "dungeon.xml";
+
+#[derive(Serialize, Deserialize)]
+struct DungeonXml {
+    #[serde(rename = "$text")]
+    payload: String,
+}
+
+fn serialize_dungeon(save_data: &DungeonSave) -> Result<Vec<u8>, String> {
+    let payload = serde_json::to_string(save_data)
+        .map_err(|e| format!("Failed to serialize dungeon: {e}"))?;
+    quick_xml::se::to_string(&DungeonXml { payload })
+        .map(|xml| {
+            let mut document = String::from("<?xml version=\"1.0\" encoding=\"UTF-8\"?>\n");
+            document.push_str(&xml);
+            document.into_bytes()
+        })
+        .map_err(|e| format!("Failed to serialize dungeon: {e}"))
+}
+
+fn deserialize_dungeon(xml: &[u8]) -> Result<DungeonSave, String> {
+    let document: DungeonXml = quick_xml::de::from_reader(Cursor::new(xml))
+        .map_err(|e| format!("Failed to parse dungeon XML: {e}"))?;
+    serde_json::from_str(&document.payload)
+        .map_err(|e| format!("Failed to parse dungeon XML payload: {e}"))
+}
+
+fn create_archive(save_data: &DungeonSave) -> Result<Vec<u8>, String> {
+    let xml = serialize_dungeon(save_data)?;
+    let mut archive = Cursor::new(Vec::new());
+    {
+        let mut writer = ZipWriter::new(&mut archive);
+        let options = SimpleFileOptions::default().compression_method(CompressionMethod::Deflated);
+        writer
+            .start_file(XML_ENTRY_NAME, options)
+            .map_err(|e| format!("Failed to create dungeon archive: {e}"))?;
+        writer
+            .write_all(&xml)
+            .map_err(|e| format!("Failed to write dungeon XML: {e}"))?;
+        writer
+            .finish()
+            .map_err(|e| format!("Failed to finish dungeon archive: {e}"))?;
+    }
+    Ok(archive.into_inner())
+}
+
+fn read_archive(bytes: &[u8]) -> Result<DungeonSave, String> {
+    let mut archive =
+        ZipArchive::new(Cursor::new(bytes)).map_err(|e| format!("Invalid dungeon archive: {e}"))?;
+    let mut xml_file = archive
+        .by_name(XML_ENTRY_NAME)
+        .map_err(|e| format!("Dungeon archive is missing {XML_ENTRY_NAME}: {e}"))?;
+    let mut xml = Vec::new();
+    xml_file
+        .read_to_end(&mut xml)
+        .map_err(|e| format!("Failed to read dungeon XML: {e}"))?;
+    deserialize_dungeon(&xml)
+}
+
+// Saves dungeon state to a compressed XML archive.
 pub fn save_dungeon(
     settings: &UiSettings,
     layouts: Vec<DungeonLayout>,
@@ -27,8 +89,8 @@ pub fn save_dungeon(
 ) -> Result<PathBuf, String> {
     let dialog = FileDialog::new()
         .set_title("Save Dungeon State")
-        .add_filter("Dungeon File", &["dungeon"])
-        .set_file_name("my_dungeon.dungeon");
+        .add_filter("Dungeon File", &["dun"])
+        .set_file_name("my_dungeon.dun");
 
     #[cfg(target_os = "windows")]
     let path = std::thread::spawn(move || dialog.save_file())
@@ -37,7 +99,10 @@ pub fn save_dungeon(
     #[cfg(not(target_os = "windows"))]
     let path = dialog.save_file();
 
-    let path = path.ok_or_else(|| "Save canceled".to_string())?;
+    let mut path = path.ok_or_else(|| "Save canceled".to_string())?;
+    if path.extension().is_none() {
+        path.set_extension("dun");
+    }
 
     let save_data = DungeonSave {
         settings: settings.clone(),
@@ -45,19 +110,17 @@ pub fn save_dungeon(
         svgs,
     };
 
-    let json = serde_json::to_string_pretty(&save_data)
-        .map_err(|e| format!("Failed to serialize dungeon: {e}"))?;
-
-    fs::write(&path, json).map_err(|e| format!("Failed to write file: {e}"))?;
+    let archive = create_archive(&save_data)?;
+    fs::write(&path, archive).map_err(|e| format!("Failed to write file: {e}"))?;
 
     Ok(path)
 }
 
-// Loads dungeon state from a user-selected JSON file.
+// Loads dungeon state from a compressed XML archive.
 pub fn load_dungeon() -> Result<DungeonSave, String> {
     let dialog = FileDialog::new()
         .set_title("Load Dungeon State")
-        .add_filter("Dungeon File", &["dungeon"]);
+        .add_filter("Dungeon File", &["dun"]);
 
     #[cfg(target_os = "windows")]
     let path = std::thread::spawn(move || dialog.pick_file())
@@ -68,10 +131,55 @@ pub fn load_dungeon() -> Result<DungeonSave, String> {
 
     let path = path.ok_or_else(|| "Load canceled".to_string())?;
 
-    let content = fs::read_to_string(path).map_err(|e| format!("Failed to read file: {e}"))?;
+    let content = fs::read(path).map_err(|e| format!("Failed to read file: {e}"))?;
+    read_archive(&content)
+}
 
-    let save_data: DungeonSave =
-        serde_json::from_str(&content).map_err(|e| format!("Failed to parse dungeon file: {e}"))?;
+#[cfg(test)]
+mod tests {
+    use super::*;
 
-    Ok(save_data)
+    #[test]
+    fn archive_round_trip_preserves_saved_data() {
+        let save = DungeonSave {
+            settings: UiSettings::default(),
+            layouts: vec![DungeonLayout {
+                name: "Level 1".to_string(),
+                rooms: vec![crate::layout::types::Room {
+                    x: 2,
+                    y: 3,
+                    width: 5,
+                    height: 4,
+                }],
+                text_labels: vec![crate::layout::types::TextLabel {
+                    cell: (4, 5),
+                    text: "Keep & escape".to_string(),
+                    font_size: 18,
+                }],
+                ..DungeonLayout::default()
+            }],
+            svgs: vec!["<svg><text>test &amp;</text></svg>".to_string()],
+        };
+
+        let archive = create_archive(&save).expect("archive should serialize");
+        let restored = read_archive(&archive).expect("archive should deserialize");
+
+        assert_eq!(restored.settings, save.settings);
+        assert_eq!(restored.layouts, save.layouts);
+        assert_eq!(restored.svgs, save.svgs);
+    }
+
+    #[test]
+    fn archive_uses_deflate_compression() {
+        let save = DungeonSave {
+            settings: UiSettings::default(),
+            layouts: Vec::new(),
+            svgs: vec!["<svg>".repeat(100)],
+        };
+        let archive = create_archive(&save).expect("archive should serialize");
+        let mut zip = ZipArchive::new(Cursor::new(archive)).expect("archive should be valid");
+        let entry = zip.by_name(XML_ENTRY_NAME).expect("XML entry should exist");
+
+        assert_eq!(entry.compression(), CompressionMethod::Deflated);
+    }
 }

src/ui/types.rs

@@ -135,6 +135,7 @@ pub struct UiSettings {
     pub export_height: u32,
     pub allow_export_aspect_change: bool,
     pub export_show_grid: bool,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub last_export_path: Option<String>,
     pub add_tool: AddTool,
     pub add_text_value: String,
@@ -156,6 +157,7 @@ pub struct UiSettings {
     pub min_levels: usize,
     pub max_levels: usize,
     pub active_level_index: usize,
+    #[serde(skip_serializing_if = "Option::is_none")]
     pub overlay_level_index: Option<usize>,
     pub export_level_index: usize,
     pub trap_frequency_percent: usize,