[egui_web] Auto-save app state to Local Storage every 30 seconds

egui_web/CHANGELOG.md

@@ -7,6 +7,10 @@ The format is based on [Keep a Changelog](https://keepachangelog.com/en/1.0.0/).
 
 ## Unreleased
 
+### Added ⭐
+
+* Auto-save of app state to local storage
+
 ### Changed ⭐
 
 * Set a maximum canvas size to alleviate performance issues on some machines

egui_web/src/backend.rs

@@ -12,19 +12,16 @@ pub struct WebBackend {
     painter: webgl::Painter,
     previous_frame_time: Option<f32>,
     frame_start: Option<f64>,
-    last_save_time: Option<f64>,
 }
 
 impl WebBackend {
     pub fn new(canvas_id: &str) -> Result<Self, JsValue> {
         let ctx = egui::CtxRef::default();
-        load_memory(&ctx);
         Ok(Self {
             ctx,
             painter: webgl::Painter::new(canvas_id)?,
             previous_frame_time: None,
             frame_start: None,
-            last_save_time: None,
         })
     }
 
@@ -47,8 +44,6 @@ impl WebBackend {
         let (output, paint_commands) = self.ctx.end_frame();
         let paint_jobs = self.ctx.tesselate(paint_commands);
 
-        self.auto_save();
-
         let now = now_sec();
         self.previous_frame_time = Some((now - frame_start) as f32);
 
@@ -68,16 +63,6 @@ impl WebBackend {
         )
     }
 
-    pub fn auto_save(&mut self) {
-        let now = now_sec();
-        let time_since_last_save = now - self.last_save_time.unwrap_or(std::f64::NEG_INFINITY);
-        const AUTO_SAVE_INTERVAL: f64 = 5.0;
-        if time_since_last_save > AUTO_SAVE_INTERVAL {
-            self.last_save_time = Some(now);
-            save_memory(&self.ctx);
-        }
-    }
-
     pub fn painter_debug_info(&self) -> String {
         self.painter.debug_info()
     }
@@ -159,19 +144,37 @@ pub struct AppRunner {
     pub input: WebInput,
     pub app: Box<dyn App>,
     pub needs_repaint: std::sync::Arc<NeedRepaint>,
+    pub storage: LocalStorage,
+    pub last_save_time: f64,
 }
 
 impl AppRunner {
     pub fn new(web_backend: WebBackend, mut app: Box<dyn App>) -> Result<Self, JsValue> {
+        load_memory(&web_backend.ctx);
+        let storage = LocalStorage::default();
+        app.load(&storage);
         app.setup(&web_backend.ctx);
         Ok(Self {
             web_backend,
             input: Default::default(),
             app,
             needs_repaint: Default::default(),
+            storage,
+            last_save_time: now_sec(),
         })
     }
 
+    pub fn auto_save(&mut self) {
+        let now = now_sec();
+        let time_since_last_save = now - self.last_save_time;
+
+        if time_since_last_save > self.app.auto_save_interval().as_secs_f64() {
+            save_memory(&self.web_backend.ctx);
+            self.app.save(&mut self.storage);
+            self.last_save_time = now;
+        }
+    }
+
     pub fn canvas_id(&self) -> &str {
         self.web_backend.canvas_id()
     }

egui_web/src/lib.rs

@@ -152,7 +152,7 @@ pub fn load_memory(ctx: &egui::Context) {
                 *ctx.memory() = memory;
             }
             Err(err) => {
-                console_log(format!("ERROR: Failed to parse memory json: {}", err));
+                console_error(format!("Failed to parse memory json: {}", err));
             }
         }
     }
@@ -164,14 +164,12 @@ pub fn save_memory(ctx: &egui::Context) {
             local_storage_set("egui_memory_json", &json);
         }
         Err(err) => {
-            console_log(format!(
-                "ERROR: Failed to serialize memory as json: {}",
-                err
-            ));
+            console_error(format!("Failed to serialize memory as json: {}", err));
         }
     }
 }
 
+#[derive(Default)]
 pub struct LocalStorage {}
 
 impl egui::app::Storage for LocalStorage {
@@ -220,7 +218,7 @@ pub fn set_clipboard_text(s: &str) {
         let future = wasm_bindgen_futures::JsFuture::from(promise);
         let future = async move {
             if let Err(err) = future.await {
-                console_log(format!("Copy/cut action denied: {:?}", err));
+                console_error(format!("Copy/cut action denied: {:?}", err));
             }
         };
         wasm_bindgen_futures::spawn_local(future);
@@ -341,7 +339,9 @@ fn paint_and_schedule(runner_ref: AppRunnerRef) -> Result<(), JsValue> {
             if output.needs_repaint {
                 runner_lock.needs_repaint.set_true();
             }
+            runner_lock.auto_save();
         }
+
         Ok(())
     }