feat(core,gui): remember the main window's size

The app always opened at 980x680. It now keeps the unmaximized size and
whether the window was maximized in config.json under `window`, written
when the window closes and when the app quits with it still open. A
missing field, or a saved size below 480x400, opens at the old default.

crates/pdfs-core/src/config.rs

@@ -163,6 +163,10 @@ pub struct AppConfig {
     /// Defaulted for configs predating the field.
     #[serde(default)]
     pub files_view: FilesView,
+    /// The desktop app's main window size, remembered between runs. Defaulted
+    /// for configs predating the field.
+    #[serde(default)]
+    pub window: WindowState,
     /// The user hid the tray icon from its own menu. The tray exits at start
     /// while this is set, and the app does not spawn it; Preferences turns it
     /// back on. Defaulted for configs predating the field.
@@ -211,6 +215,44 @@ impl Default for FilesView {
     }
 }
 
+/// The desktop app's main window, as it was when it last closed.
+#[derive(Serialize, Deserialize, Debug, Clone, Copy, PartialEq, Eq)]
+#[serde(default)]
+pub struct WindowState {
+    /// The unmaximised size, in logical pixels.
+    pub width: i32,
+    pub height: i32,
+    pub maximized: bool,
+}
+
+impl WindowState {
+    /// Below this the saved size is taken for damage and the default is used.
+    pub const MIN_WIDTH: i32 = 480;
+    pub const MIN_HEIGHT: i32 = 400;
+
+    /// This state, with a size too small to use replaced by the default.
+    pub fn usable(self) -> Self {
+        if self.width < Self::MIN_WIDTH || self.height < Self::MIN_HEIGHT {
+            Self {
+                maximized: self.maximized,
+                ..Self::default()
+            }
+        } else {
+            self
+        }
+    }
+}
+
+impl Default for WindowState {
+    fn default() -> Self {
+        Self {
+            width: 980,
+            height: 680,
+            maximized: false,
+        }
+    }
+}
+
 /// The key a My Files listing is ordered by.
 #[derive(Serialize, Deserialize, Debug, Clone, Copy, PartialEq, Eq, Default)]
 #[serde(rename_all = "lowercase")]
@@ -702,6 +744,11 @@ mod tests {
                 descending: true,
                 folders_first: false,
             },
+            window: WindowState {
+                width: 1200,
+                height: 800,
+                maximized: true,
+            },
             tray_hidden: true,
             language: Some("de".to_string()),
             online_map: true,
@@ -721,6 +768,39 @@ mod tests {
         assert_eq!(decoded.upload_limit, Some(500_000));
         assert_eq!(decoded.download_limit, None);
         assert_eq!(decoded.files_view, config.files_view);
+        assert_eq!(decoded.window, config.window);
+    }
+
+    #[test]
+    fn a_config_without_a_window_opens_at_the_default_size() {
+        let decoded: AppConfig =
+            serde_json::from_str(r#"{"app_version":"a","user_agent":"b"}"#).unwrap();
+        assert_eq!(decoded.window, WindowState::default());
+        let partial: WindowState = serde_json::from_str(r#"{"maximized":true}"#).unwrap();
+        assert_eq!((partial.width, partial.height), (980, 680));
+        assert!(partial.maximized);
+    }
+
+    #[test]
+    fn a_window_saved_too_small_opens_at_the_default_size() {
+        let tiny = WindowState {
+            width: 0,
+            height: 500,
+            maximized: true,
+        };
+        assert_eq!(
+            tiny.usable(),
+            WindowState {
+                maximized: true,
+                ..WindowState::default()
+            }
+        );
+        let fine = WindowState {
+            width: 640,
+            height: 480,
+            maximized: false,
+        };
+        assert_eq!(fine.usable(), fine);
     }
 
     #[test]

crates/pdfs-gui/src/app/main.rs

@@ -69,7 +69,7 @@ use gtk4::glib::BoxedAnyObject;
 
 use pdfs_core::auth;
 
-use pdfs_core::config::{AppDirs, FileSort, FilesView};
+use pdfs_core::config::{AppDirs, FileSort, FilesView, WindowState};
 
 use pdfs_core::control::{
     ActivityEntry, ActivityKind, AlbumInfo, BookmarkInfo, ConflictInfo, ConflictKeep, DeviceInfo,
@@ -716,13 +716,18 @@ fn build_window(app: &adw::Application) {
         }
     });
 
+    let saved = ui.dirs.load_config().window.usable();
     let window = adw::ApplicationWindow::builder()
         .application(app)
         .title("Proton Drive")
-        .default_width(980)
-        .default_height(680)
+        .default_width(saved.width)
+        .default_height(saved.height)
+        .maximized(saved.maximized)
+        .width_request(WindowState::MIN_WIDTH)
+        .height_request(WindowState::MIN_HEIGHT)
         .content(&toasts)
         .build();
+    remember_window_state(&ui, app, &window);
     // A wide window docks the details pane beside the files instead of laying it
     // over them.
     let wide = adw::Breakpoint::new(
@@ -743,6 +748,42 @@ fn build_window(app: &adw::Application) {
     window.present();
 }
 
+/// Save the window's size when it closes, and when the app quits with the
+/// window still open (Ctrl+Q, the tray's Quit), which never asks it to close.
+fn remember_window_state(ui: &Rc<Ui>, app: &adw::Application, window: &adw::ApplicationWindow) {
+    let ui_close = ui.clone();
+    window.connect_close_request(move |window| {
+        save_window_state(&ui_close, window);
+        glib::Propagation::Proceed
+    });
+    let ui_quit = ui.clone();
+    let window_quit = window.downgrade();
+    app.connect_shutdown(move |_| {
+        if let Some(window) = window_quit.upgrade() {
+            save_window_state(&ui_quit, &window);
+        }
+    });
+}
+
+/// Write the window's unmaximised size and maximised state to the config, if
+/// either changed. Runs as the window goes away, so a failure is only logged.
+fn save_window_state(ui: &Ui, window: &adw::ApplicationWindow) {
+    let (width, height) = window.default_size();
+    let state = WindowState {
+        width,
+        height,
+        maximized: window.is_maximized(),
+    };
+    let mut config = ui.dirs.load_config();
+    if config.window == state {
+        return;
+    }
+    config.window = state;
+    if let Err(e) = ui.dirs.save_config(&config) {
+        tracing::warn!("cannot save the window size: {e}");
+    }
+}
+
 /// Whether `window` is minimised or otherwise out of sight (another workspace,
 /// fully covered), as far as the compositor tells us.
 fn window_hidden(window: &adw::ApplicationWindow) -> bool {