refactor: change app handle setup to use a condition variable

src-tauri/src/app_handle.rs

@@ -0,0 +1,25 @@
+use std::sync::{Condvar, Mutex};
+
+use tauri::{App, AppHandle};
+
+static APP_HANDLE_MUTEX: Mutex<Option<AppHandle>> = Mutex::new(None);
+
+static APP_HANDLE_CONDVAR: Condvar = Condvar::new();
+
+/// Setup the static app handle and notify waiting threads.
+pub fn setup(app: &mut App) {
+    let mut app_handle = APP_HANDLE_MUTEX.lock().unwrap();
+    *app_handle = Some(app.handle());
+    APP_HANDLE_CONDVAR.notify_all();
+}
+
+/// Get the app handle but block the current thread until it is available.
+///
+/// The app handle is made available via [`setup`].
+pub fn get_app_handle() -> AppHandle {
+    let mut app_handle = APP_HANDLE_MUTEX.lock().unwrap();
+    while app_handle.is_none() {
+        app_handle = APP_HANDLE_CONDVAR.wait(app_handle).unwrap();
+    }
+    app_handle.as_ref().unwrap().clone()
+}

src-tauri/src/command/ocr.rs

@@ -3,7 +3,8 @@ use std::path::PathBuf;
 use tesseract::Tesseract;
 
 use crate::{
-    command::error::CommandError, entity_crud, entity_crud::EntityCrudTrait, get_app_handle,
+    app_handle::get_app_handle, command::error::CommandError, entity_crud,
+    entity_crud::EntityCrudTrait,
 };
 
 /// Get the optically recognized characters from the specified recipe file.

src-tauri/src/main.rs

@@ -3,7 +3,7 @@
     windows_subsystem = "windows"
 )]
 
-use tauri::{AppHandle, Wry};
+use tauri::Wry;
 
 use crate::command::{
     entity::{
@@ -44,6 +44,7 @@ use crate::command::{
     unit_list::unit_list_get,
 };
 
+mod app_handle;
 mod command;
 mod database;
 mod dom_content_loaded;
@@ -60,25 +61,6 @@ mod scraper;
 mod unit_conversion;
 mod window;
 
-/// This static variable holds the app handle once the tauri app has started.
-static mut APP_HANDLE: Option<AppHandle> = None;
-
-/// Get and unwrap the static app handle [`APP_HANDLE`].
-///
-/// See [`try_get_app_handle`] for a non-panicing version.
-///
-/// # Panics
-///
-/// This function panics when [`APP_HANDLE`] is [`None`]. this is the case when the tauri app is un-initialized.
-pub fn get_app_handle() -> &'static AppHandle {
-    try_get_app_handle().expect("Could not get the app handle.")
-}
-
-/// Get the static app handle [`APP_HANDLE`].
-pub fn try_get_app_handle() -> Option<&'static AppHandle> {
-    unsafe { APP_HANDLE.as_ref() }
-}
-
 #[tokio::main]
 async fn main() {
     setup()
@@ -89,9 +71,7 @@ async fn main() {
 fn setup() -> tauri::Builder<Wry> {
     tauri::Builder::default()
         .setup(|app| {
-            unsafe {
-                APP_HANDLE = Some(app.handle());
-            }
+            app_handle::setup(app);
             log::init();
             dom_content_loaded::setup(app);
             Ok(())

src-tauri/src/path.rs

@@ -2,7 +2,7 @@
 
 use std::{fs::create_dir_all, path::PathBuf};
 
-use crate::get_app_handle;
+use crate::app_handle::get_app_handle;
 
 macro_rules! mutable_or_immutable {
     ($var_name:ident, $var_value:expr) => {

src-tauri/src/window.rs

@@ -2,16 +2,13 @@
 
 use tauri::{Manager, Window};
 
-use crate::try_get_app_handle;
+use crate::app_handle::get_app_handle;
 
 /// Try to get the main window.
 ///
-/// Returns [`None`] when the [`try_get_app_handle`] returns [`None`].
+/// Returns [`None`] when the window with label `main` does not exist.
 pub fn try_get_window() -> Option<Window> {
-    match try_get_app_handle() {
-        Some(app_handle) => app_handle.get_window("main"),
-        _ => None,
-    }
+    get_app_handle().get_window("main")
 }
 
 /// Get the main window.