agent: rust — add preferences webview injection for zero-flash hydration

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

src-tauri/Cargo.toml

@@ -35,3 +35,4 @@ serde_json = "1"
 tokio = { version = "1", features = ["rt", "sync"] }
 arboard = "3.6.1"
 tauri-plugin-mcp = "0.7.1"
+sqlx = { version = "0.8", features = ["sqlite", "runtime-tokio"] }

src-tauri/src/commands/windows.rs

@@ -1,5 +1,7 @@
 use tauri::{Emitter, Manager, WebviewUrl, WebviewWindowBuilder};
 
+use crate::PreferencesScript;
+
 /// Open a floating always-on-top task window.
 #[tauri::command]
 pub async fn open_task_window(
@@ -13,7 +15,7 @@ pub async fn open_task_window(
         return Ok(());
     }
 
-    WebviewWindowBuilder::new(
+    let mut builder = WebviewWindowBuilder::new(
         &app,
         "tasks-float",
         WebviewUrl::App("/float".into()),
@@ -23,9 +25,16 @@ pub async fn open_task_window(
     .min_inner_size(400.0, 400.0)
     .always_on_top(true)
     .decorations(false)
-    .resizable(true)
+    .resizable(true);
-    .build()
+
-    .map_err(|e| e.to_string())?;
+    // Inject preferences before Svelte mounts
+    if let Some(script) = app.try_state::<PreferencesScript>() {
+        if !script.0.is_empty() {
+            builder = builder.initialization_script(&script.0);
+        }
+    }
+
+    builder.build().map_err(|e| e.to_string())?;
 
     Ok(())
 }
@@ -41,7 +50,7 @@ pub async fn open_viewer_window(
         return Ok(());
     }
 
-    WebviewWindowBuilder::new(
+    let mut builder = WebviewWindowBuilder::new(
         &app,
         "transcript-viewer",
         WebviewUrl::App("/viewer".into()),
@@ -50,9 +59,16 @@ pub async fn open_viewer_window(
     .inner_size(600.0, 700.0)
     .min_inner_size(450.0, 500.0)
     .decorations(false)
-    .resizable(true)
+    .resizable(true);
-    .build()
+
-    .map_err(|e| e.to_string())?;
+    // Inject preferences before Svelte mounts
+    if let Some(script) = app.try_state::<PreferencesScript>() {
+        if !script.0.is_empty() {
+            builder = builder.initialization_script(&script.0);
+        }
+    }
+
+    builder.build().map_err(|e| e.to_string())?;
 
     Ok(())
 }

src-tauri/src/lib.rs

@@ -3,15 +3,67 @@ mod tray;
 
 use std::sync::Arc;
 
+use sqlx::SqlitePool;
 use tauri::Manager;
 
 use kon_core::types::EngineName;
+use kon_storage::{database_path, get_setting, init as init_db, set_setting};
 use kon_transcription::LocalEngine;
 
-/// Shared app state holding the transcription engines.
+/// Shared app state holding the transcription engines and database pool.
 pub struct AppState {
     pub whisper_engine: Arc<LocalEngine>,
     pub parakeet_engine: Arc<LocalEngine>,
+    pub db: SqlitePool,
+}
+
+/// Holds the preferences init script for injection into secondary windows.
+pub struct PreferencesScript(pub String);
+
+/// Build a JavaScript snippet that applies saved preferences to the DOM
+/// before Svelte mounts, preventing any flash of unstyled content.
+fn build_preferences_script(prefs_json: Option<String>) -> String {
+    let json = prefs_json.unwrap_or_default();
+    if json.is_empty() {
+        return String::new();
+    }
+    // Serialise the JSON string as a JS string literal for safe embedding
+    let js_str = serde_json::to_string(&json).unwrap_or_else(|_| "\"\"".to_string());
+    format!(
+        r#"(function() {{
+  try {{
+    var p = JSON.parse({js_str});
+    var el = document.documentElement;
+    if (p.theme === 'system') {{
+      el.dataset.theme = window.matchMedia('(prefers-color-scheme: light)').matches ? 'light' : 'dark';
+    }} else if (p.theme) {{
+      el.dataset.theme = p.theme;
+    }}
+    if (p.zone && p.zone !== 'default') el.dataset.zone = p.zone;
+    if (p.accessibility) {{
+      var a = p.accessibility;
+      var fonts = {{ lexend: "'Lexend', system-ui, sans-serif", atkinson: "'Atkinson Hyperlegible Next', system-ui, sans-serif", opendyslexic: "'OpenDyslexic', system-ui, sans-serif" }};
+      if (a.fontFamily) {{ el.style.setProperty('--font-family-body', fonts[a.fontFamily] || fonts.lexend); el.dataset.fontFamily = a.fontFamily; }}
+      if (a.fontSize) el.style.setProperty('--font-size-body', a.fontSize + 'px');
+      if (a.letterSpacing != null) el.style.setProperty('--letter-spacing-body', a.letterSpacing + 'em');
+      if (a.lineHeight) el.style.setProperty('--line-height-body', String(a.lineHeight));
+      if (a.bionicReading) el.dataset.bionicReading = 'true';
+      if (a.reduceMotion === 'on' || (a.reduceMotion === 'system' && window.matchMedia('(prefers-reduced-motion: reduce)').matches)) el.dataset.reduceMotion = 'true';
+    }}
+  }} catch (e) {{ console.warn('Preferences injection failed:', e); }}
+}})();"#
+    )
+}
+
+/// Save preferences JSON to the SQLite settings table.
+#[tauri::command]
+async fn save_preferences(
+    state: tauri::State<'_, AppState>,
+    preferences: String,
+) -> Result<(), String> {
+    set_setting(&state.db, "kon_preferences", &preferences)
+        .await
+        .map_err(|e| e.to_string())
 }
 
 #[cfg_attr(mobile, tauri::mobile_entry_point)]
@@ -20,35 +72,60 @@ pub fn run() {
         .plugin(tauri_plugin_opener::init())
         .plugin(tauri_plugin_dialog::init())
         .plugin(tauri_plugin_global_shortcut::Builder::new().build())
-        .manage(AppState {
-            whisper_engine: Arc::new(LocalEngine::new(
-                EngineName::new("whisper"),
-            )),
-            parakeet_engine: Arc::new(LocalEngine::new(
-                EngineName::new("parakeet"),
-            )),
-        })
         .setup(|app| {
-            if let Err(e) = tray::setup(app) {
+            // Initialise database (blocking in setup — runs once at startup)
-                eprintln!("Failed to setup tray: {e}");
+            let db_path = database_path();
-            }
+            let db = tauri::async_runtime::block_on(async {
+                init_db(&db_path).await
+            })
+            .map_err(|e| Box::new(e) as Box<dyn std::error::Error>)?;
 
-            // Close-to-tray: hide window instead of exiting
+            // Load saved preferences for webview injection
+            let prefs_json = tauri::async_runtime::block_on(async {
+                get_setting(&db, "kon_preferences").await.unwrap_or(None)
+            });
+            let init_script = build_preferences_script(prefs_json);
+
+            // Apply preferences to the main window (defined in tauri.conf.json)
             if let Some(main_window) = app.get_webview_window("main") {
+                if !init_script.is_empty() {
+                    // Tauri's WebviewWindow.eval() is the standard API for
+                    // running JS in a webview — not the JS eval() function
+                    let _ = main_window.eval(&init_script);
+                }
+
+                // Close-to-tray: hide window instead of exiting
                 let win = main_window.clone();
                 main_window.on_window_event(move |event| {
-                    if let tauri::WindowEvent::CloseRequested { api, .. } =
+                    if let tauri::WindowEvent::CloseRequested { api, .. } = event {
-                        event
-                    {
                         api.prevent_close();
                         let _ = win.hide();
                     }
                 });
             }
 
+            // Store init script for secondary windows (float, viewer)
+            app.manage(PreferencesScript(init_script));
+
+            app.manage(AppState {
+                whisper_engine: Arc::new(LocalEngine::new(
+                    EngineName::new("whisper"),
+                )),
+                parakeet_engine: Arc::new(LocalEngine::new(
+                    EngineName::new("parakeet"),
+                )),
+                db,
+            });
+
+            if let Err(e) = tray::setup(app) {
+                eprintln!("Failed to setup tray: {e}");
+            }
+
             Ok(())
         })
         .invoke_handler(tauri::generate_handler![
+            // Preferences
+            save_preferences,
             // Whisper model management
             commands::models::download_model,
             commands::models::check_model,