made settings persistant

Cargo.toml

@@ -5,3 +5,6 @@ edition = "2024"
 
 [dependencies]
 eframe = "0.31"
+serde = { version = "1", features = ["derive"] }
+serde_json = "1"
+dirs = "6"

README.md

@@ -21,7 +21,6 @@ A Rust desktop app for generating simple tabletop dungeon layouts.
 - Generate control:
   - Master seed input (`u64`)
   - `Random` seed button
-  - `Generate New Layout` button generates using the current seed
 
 ## Generation Behavior
 
@@ -56,3 +55,6 @@ cargo run
 
 - Rendering is vector-based in-app (`egui` painter), so zooming/scaling the preview remains crisp.
 - Room and corridor vectors are stored separately to support future export workflows (for example, SVG export).
+- Settings are persisted on exit and restored on startup from:
+  - Windows: `%LOCALAPPDATA%/desktop_dungeon_generator/settings.json`
+  - Linux: `~/.local/share/desktop_dungeon_generator/settings.json` (or distro-equivalent local data dir)

src/main.rs

@@ -1,4 +1,5 @@
 mod layout;
+mod persistence;
 mod seed;
 mod ui;
 
@@ -26,7 +27,7 @@ struct DungeonApp {
 
 impl Default for DungeonApp {
     fn default() -> Self {
-        let settings = UiSettings::default();
+        let settings = persistence::load_settings().unwrap_or_default();
         let layout = generate_layout(
             settings.cols,
             settings.rows,
@@ -43,6 +44,14 @@ impl Default for DungeonApp {
     }
 }
 
+impl Drop for DungeonApp {
+    fn drop(&mut self) {
+        if let Err(err) = persistence::save_settings(&self.settings) {
+            eprintln!("Failed to save settings: {err}");
+        }
+    }
+}
+
 impl eframe::App for DungeonApp {
     fn update(&mut self, ctx: &egui::Context, _frame: &mut eframe::Frame) {
         let panel_result = draw_side_panel(ctx, &mut self.settings);

src/persistence.rs

@@ -0,0 +1,36 @@
+use std::fs;
+use std::io;
+use std::path::PathBuf;
+
+use crate::ui::UiSettings;
+
+const APP_DIR_NAME: &str = "desktop_dungeon_generator";
+const SETTINGS_FILE_NAME: &str = "settings.json";
+
+pub fn load_settings() -> Option<UiSettings> {
+    let path = settings_path()?;
+    let content = fs::read_to_string(path).ok()?;
+    serde_json::from_str::<UiSettings>(&content).ok()
+}
+
+pub fn save_settings(settings: &UiSettings) -> io::Result<()> {
+    let path = settings_path().ok_or_else(|| {
+        io::Error::new(
+            io::ErrorKind::NotFound,
+            "No OS application data directory found",
+        )
+    })?;
+
+    if let Some(parent) = path.parent() {
+        fs::create_dir_all(parent)?;
+    }
+
+    let json = serde_json::to_string_pretty(settings)
+        .map_err(|err| io::Error::new(io::ErrorKind::InvalidData, err))?;
+    fs::write(path, json)
+}
+
+fn settings_path() -> Option<PathBuf> {
+    let base = dirs::data_local_dir().or_else(dirs::data_dir)?;
+    Some(base.join(APP_DIR_NAME).join(SETTINGS_FILE_NAME))
+}

src/ui.rs

@@ -1,14 +1,22 @@
 use crate::seed;
 use eframe::egui;
 use egui::RichText;
+use serde::{Deserialize, Serialize};
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Serialize, Deserialize)]
 enum Tab {
     Generate,
     Layout,
 }
 
-#[derive(Debug, Clone)]
+impl Default for Tab {
+    fn default() -> Self {
+        Self::Generate
+    }
+}
+
+#[derive(Debug, Clone, Serialize, Deserialize)]
+#[serde(default)]
 pub struct UiSettings {
     pub seed: u64,
     pub cols: usize,