Fix panic messages being invisible in tui mode (#2226)

* Fix panic messages being invisible in tui mode

Currently when a panic happens the message gets printed to the alternate screen which gets erased after the terminal is reset to raw mode in the TuiMetricsRenderer drop code.

That leaves users unable to see the panic message (issue #2062).

This commit changes TuiMetricsRenderer to reset the terminal first during a panic and then running the panic handler.

* Use PanicInfo to support Rust version < 1.82

Author: PaulWagener

crates/burn-train/src/renderer/tui/renderer.rs

@@ -7,6 +7,8 @@ use crossterm::{
     terminal::{disable_raw_mode, enable_raw_mode, EnterAlternateScreen, LeaveAlternateScreen},
 };
 use ratatui::{prelude::*, Terminal};
+use std::panic::{set_hook, take_hook};
+use std::sync::Arc;
 use std::{
     error::Error,
     io::{self, Stdout},
@@ -23,6 +25,9 @@ pub(crate) type TerminalBackend = CrosstermBackend<Stdout>;
 /// The current terminal frame.
 pub(crate) type TerminalFrame<'a> = ratatui::Frame<'a>;
 
+#[allow(deprecated)] // `PanicInfo` type is renamed to `PanicHookInfo` in Rust 1.82
+type PanicHook = Box<dyn Fn(&std::panic::PanicInfo<'_>) + 'static + Sync + Send>;
+
 const MAX_REFRESH_RATE_MILLIS: u64 = 100;
 
 /// The terminal UI metrics renderer.
@@ -35,6 +40,7 @@ pub struct TuiMetricsRenderer {
     status: StatusState,
     interuptor: TrainingInterrupter,
     popup: PopupState,
+    previous_panic_hook: Option<Arc<PanicHook>>,
 }
 
 impl MetricsRenderer for TuiMetricsRenderer {
@@ -85,6 +91,18 @@ impl TuiMetricsRenderer {
         enable_raw_mode().unwrap();
         let terminal = Terminal::new(CrosstermBackend::new(stdout)).unwrap();
 
+        // Reset the terminal to raw mode on panic before running the panic handler
+        // This prevents that the panic message is not visible for the user.
+        let previous_panic_hook = Arc::new(take_hook());
+        set_hook(Box::new({
+            let previous_panic_hook = previous_panic_hook.clone();
+            move |panic_info| {
+                let _ = disable_raw_mode();
+                let _ = execute!(io::stdout(), LeaveAlternateScreen);
+                previous_panic_hook(panic_info);
+            }
+        }));
+
         Self {
             terminal,
             last_update: Instant::now(),
@@ -94,6 +112,7 @@ impl TuiMetricsRenderer {
             status: StatusState::default(),
             interuptor,
             popup: PopupState::Empty,
+            previous_panic_hook: Some(previous_panic_hook),
         }
     }
 
@@ -205,8 +224,20 @@ impl CallbackFn for PopupCancel {
 
 impl Drop for TuiMetricsRenderer {
     fn drop(&mut self) {
-        disable_raw_mode().ok();
-        execute!(self.terminal.backend_mut(), LeaveAlternateScreen).unwrap();
-        self.terminal.show_cursor().ok();
+        // Reset the terminal back to raw mode. This can be skipped during
+        // panicking because the panic hook has already reset the terminal
+        if !std::thread::panicking() {
+            disable_raw_mode().ok();
+            execute!(self.terminal.backend_mut(), LeaveAlternateScreen).unwrap();
+            self.terminal.show_cursor().ok();
+
+            // Reinstall the previous panic hook
+            let _ = take_hook();
+            if let Some(previous_panic_hook) =
+                Arc::into_inner(self.previous_panic_hook.take().unwrap())
+            {
+                set_hook(previous_panic_hook);
+            }
+        }
     }
 }