More error handling improvements

src/backend/luna.rs

@@ -231,8 +231,20 @@ impl LunaStop {
     pub fn stop(self) -> Result<(), Error> {
         println!("Requesting capture stop");
         self.stop_request.send(()).context("Failed sending stop request")?;
-        self.worker.join().err().context("Worker thread panic")?;
-        Ok(())
+        match self.worker.join() {
+            Ok(result) => result,
+            Err(panic) => {
+                let msg = match (
+                    panic.downcast_ref::<&str>(),
+                    panic.downcast_ref::<String>())
+                {
+                    (Some(&s), _) => s,
+                    (_,  Some(s)) => s,
+                    (None,  None) => "<No panic message>"
+                };
+                bail!("Worker thread panic: {msg}");
+            }
+        }
     }
 }
 

src/ui.rs

@@ -838,8 +838,15 @@ pub fn stop_luna() -> Result<(), Error> {
 pub fn display_error(result: Result<(), Error>) {
     #[cfg(not(feature="test-ui-replay"))]
     if let Err(e) = result {
-        let backtrace = e.backtrace();
-        let message = format!("{e}\n\nBacktrace:\n\n{backtrace}");
+        use std::fmt::Write;
+        let mut message = format!("{e}");
+        for cause in e.chain().skip(1) {
+            write!(message, "\ncaused by: {cause} ({cause:?})").unwrap();
+        }
+        let backtrace = format!("{}", e.backtrace());
+        if backtrace != "disabled backtrace" {
+            write!(message, "\n\nBacktrace:\n{backtrace}").unwrap();
+        }
         gtk::glib::idle_add_once(move || {
             WINDOW.with(|win_opt| {
                 match win_opt.borrow().as_ref() {