feat(settings): keep the settings inside a portable suite

portable.txt puts ArtCraftLauncherData next to the exe, but the settings still went
to eframe's storage folder in the user's profile, so a suite carried on a stick lost
its settings on another computer.

path() now returns the suite's own data folder when a portable suite is detected, and
main.rs passes it as persistence_path so eframe writes the window state to the same
file. Nothing changes for a normal install.

apps/artcraft-launcher/src/main.rs

@@ -154,7 +154,15 @@ fn native_options(hidden: bool) -> eframe::NativeOptions {
     } else if let Some(icon) = icon {
         viewport = viewport.with_icon(icon);
     }
-    eframe::NativeOptions { viewport, persist_window: true, wgpu_options: wgpu_options(), ..Default::default() }
+    // Persistence goes to the same file `settings_file` uses, so a portable suite keeps its
+    // settings and window state inside itself instead of in the user's profile.
+    eframe::NativeOptions {
+        viewport,
+        persist_window: true,
+        persistence_path: settings_file::path(APP_ID),
+        wgpu_options: wgpu_options(),
+        ..Default::default()
+    }
 }
 
 /// wgpu's backend list. On Windows that is Direct3D 12 with GL as the fallback, not Vulkan:

apps/artcraft-launcher/src/settings_file.rs

@@ -8,9 +8,18 @@
 use std::collections::HashMap;
 use std::path::{Path, PathBuf};
 
-/// Where eframe keeps its state for `app_id`, as it picks it for a window with that app id.
+/// Where the settings file is. In portable mode it is inside `ArtCraftLauncherData`, so a suite
+/// carried on a stick keeps its settings when it is plugged into another computer. Without
+/// `portable.txt` it is eframe's own folder, which is in the user's profile and cannot travel.
 pub fn path(app_id: &str) -> Option<PathBuf> {
-    eframe::storage_dir(app_id).map(|dir| dir.join("app.ron"))
+    artcraft_launcher_native::paths::portable_root()
+        .map(|root| portable_settings(&root))
+        .or_else(|| eframe::storage_dir(app_id).map(|dir| dir.join("app.ron")))
+}
+
+/// The settings file inside a portable suite: the same `data` folder `Paths` already uses.
+fn portable_settings(root: &Path) -> PathBuf {
+    root.join("data").join("app.ron")
 }
 
 /// The value stored under `key`, if the file has one that still reads.
@@ -91,6 +100,12 @@ mod tests {
         }
     }
 
+    #[test]
+    fn a_portable_suite_keeps_its_settings_inside_itself() {
+        let root = PathBuf::from("E:\\Suite\\ArtCraftLauncherData");
+        assert_eq!(portable_settings(&root), PathBuf::from("E:\\Suite\\ArtCraftLauncherData\\data\\app.ron"));
+    }
+
     #[test]
     fn settings_saved_with_no_file_read_back() {
         let dir = Scratch::new("settings-round-trip");