fix(client): detach when terminal geometry is unavailable (#3531)

refs #3519

3 files changed, 85 insertions, 37 deletions

diff --git a/src/client/mod.rs b/src/client/mod.rs
index b7fdcabe..b20a6e85 100644
--- a/src/client/mod.rs
+++ b/src/client/mod.rs
@@ -36,9 +36,9 @@ pub use terminal_sessions::{run_terminal_session_control, run_terminal_session_o
 use terminal_geometry::query_host_terminal_appearance;
 #[cfg(test)]
 use terminal_geometry::{
-    cell_size_fallback, ioctl_cell_size, pack_cell_size, resize_report_required,
-    should_query_host_cell_size, write_host_cell_size_query, write_host_terminal_appearance_query,
-    write_host_terminal_theme_query,
+    cell_size_fallback, current_terminal_geometry_with, ioctl_cell_size, pack_cell_size,
+    resize_report_required, should_query_host_cell_size, write_host_cell_size_query,
+    write_host_terminal_appearance_query, write_host_terminal_theme_query,
 };
 use terminal_geometry::{
     host_cell_size_query_required, initial_terminal_geometry, query_host_cell_size,
@@ -302,6 +302,8 @@ enum ClientLoopEvent {
     StdinEvents(Vec<crate::protocol::ClientInputEvent>),
     /// Terminal resize detected, including current exact-pixel eligibility.
     Resize(u16, u16, u32, u32, bool),
+    /// The client's host terminal can no longer report a valid grid.
+    TerminalUnavailable(io::Error),
     /// Server message received.
     ServerMessage(Box<ServerMessage>),
     /// Server reader thread exited (connection lost).
@@ -400,7 +402,7 @@ fn run_client_with_mode(
 
     // Get the terminal geometry before handshake (before raw mode).
     let (cols, rows, cell_width_px, cell_height_px, exact_cell_size) =
-        initial_terminal_geometry(pixel_geometry_enabled, kitty_graphics_enabled);
+        initial_terminal_geometry(pixel_geometry_enabled, kitty_graphics_enabled)?;
 
     let shell_surface_size = loop_config
         .shell_config
@@ -1216,6 +1218,11 @@ async fn run_client_loop(
                 }
                 // Direct terminal attach is Unix-only; every Windows client uses ClientShell.
             }
+            ClientLoopEvent::TerminalUnavailable(err) => {
+                info!(err = %err, "client terminal unavailable; detaching");
+                let _ = write_to_server(&mut write_stream, &ClientMessage::Detach);
+                return Ok(());
+            }
             ClientLoopEvent::Resize(
                 new_cols,
                 new_rows,
diff --git a/src/client/terminal_geometry.rs b/src/client/terminal_geometry.rs
index d1f305ab..aaf216df 100644
--- a/src/client/terminal_geometry.rs
+++ b/src/client/terminal_geometry.rs
@@ -58,26 +58,46 @@ fn unpack_cell_size(packed: u64) -> Option<(u32, u32)> {
     (width_px > 0 && height_px > 0).then_some((width_px, height_px))
 }
 
-fn current_terminal_geometry(
+type TerminalGeometry = (u16, u16, u32, u32, bool);
+
+pub(super) fn current_terminal_geometry_with(
     pixel_geometry_enabled: bool,
     pixel_geometry_fallback: bool,
     reported_cell_size: &AtomicU64,
     last_cell_size: Option<(u32, u32)>,
-) -> (u16, u16, u32, u32, bool) {
+    exact_geometry: Option<(u16, u16, u32, u32)>,
+    terminal_grid_size: impl FnOnce() -> io::Result<(u16, u16)>,
+) -> io::Result<TerminalGeometry> {
     if !pixel_geometry_enabled {
-        let (cols, rows) = crossterm::terminal::size().unwrap_or((80, 24));
-        return (cols, rows, 0, 0, false);
+        let (cols, rows) = terminal_grid_size()?;
+        return Ok((cols, rows, 0, 0, false));
     }
-    if let Some((cols, rows, cell_width_px, cell_height_px)) = ioctl_terminal_geometry() {
-        return (cols, rows, cell_width_px, cell_height_px, true);
+    if let Some((cols, rows, cell_width_px, cell_height_px)) = exact_geometry {
+        return Ok((cols, rows, cell_width_px, cell_height_px, true));
     }
-    let (cols, rows) = crossterm::terminal::size().unwrap_or((80, 24));
+    let (cols, rows) = terminal_grid_size()?;
     if !pixel_geometry_fallback {
-        return (cols, rows, 0, 0, false);
+        return Ok((cols, rows, 0, 0, false));
     }
     let (cell_width_px, cell_height_px) =
         cell_size_fallback(reported_cell_size.load(Ordering::Acquire), last_cell_size);
-    (cols, rows, cell_width_px, cell_height_px, false)
+    Ok((cols, rows, cell_width_px, cell_height_px, false))
+}
+
+fn current_terminal_geometry(
+    pixel_geometry_enabled: bool,
+    pixel_geometry_fallback: bool,
+    reported_cell_size: &AtomicU64,
+    last_cell_size: Option<(u32, u32)>,
+) -> io::Result<TerminalGeometry> {
+    current_terminal_geometry_with(
+        pixel_geometry_enabled,
+        pixel_geometry_fallback,
+        reported_cell_size,
+        last_cell_size,
+        ioctl_terminal_geometry(),
+        crate::platform::terminal_grid_size,
+    )
 }
 
 /// Reads terminal geometry before the handshake. Pixel input and direct graphics
@@ -85,28 +105,13 @@ fn current_terminal_geometry(
 pub(super) fn initial_terminal_geometry(
     pixel_geometry_enabled: bool,
     pixel_geometry_fallback: bool,
-) -> (u16, u16, u32, u32, bool) {
-    if !pixel_geometry_enabled {
-        let (cols, rows) = crossterm::terminal::size().unwrap_or((80, 24));
-        return (cols, rows, 0, 0, false);
-    }
-    match ioctl_terminal_geometry() {
-        Some((cols, rows, width, height)) => (cols, rows, width, height, true),
-        None => {
-            let (cols, rows) = crossterm::terminal::size().unwrap_or((80, 24));
-            if pixel_geometry_fallback {
-                (
-                    cols,
-                    rows,
-                    DEFAULT_CELL_WIDTH_PX,
-                    DEFAULT_CELL_HEIGHT_PX,
-                    false,
-                )
-            } else {
-                (cols, rows, 0, 0, false)
-            }
-        }
-    }
+) -> io::Result<TerminalGeometry> {
+    current_terminal_geometry(
+        pixel_geometry_enabled,
+        pixel_geometry_fallback,
+        &AtomicU64::new(0),
+        None,
+    )
 }
 
 pub(super) fn resize_report_required(
@@ -146,12 +151,18 @@ pub(super) fn resize_poll_loop(
     while !should_quit.load(Ordering::Acquire) {
         std::thread::sleep(Duration::from_millis(100));
         let signalled = crate::platform::take_terminal_resize_signal();
-        let new_size = current_terminal_geometry(
+        let new_size = match current_terminal_geometry(
             pixel_geometry_enabled,
             pixel_geometry_fallback,
             reported_cell_size,
             Some((last_size.2, last_size.3)),
-        );
+        ) {
+            Ok(size) => size,
+            Err(err) => {
+                let _ = resize_tx.blocking_send(ClientLoopEvent::TerminalUnavailable(err));
+                break;
+            }
+        };
         if resize_report_required(signalled, new_size, last_size) {
             last_size = new_size;
             if resize_tx
diff --git a/src/client/tests/mod.rs b/src/client/tests/mod.rs
index d8f71a84..5d789444 100644
--- a/src/client/tests/mod.rs
+++ b/src/client/tests/mod.rs
@@ -18,6 +18,36 @@ fn resize_signal_reports_even_when_polled_size_is_unchanged() {
 }
 
 #[test]
+fn unavailable_terminal_grid_is_not_fabricated() {
+    let reported_cell_size = AtomicU64::new(0);
+    let err = current_terminal_geometry_with(false, false, &reported_cell_size, None, None, || {
+        Err(io::Error::new(
+            io::ErrorKind::NotConnected,
+            "terminal is gone",
+        ))
+    })
+    .expect_err("an unavailable terminal must not produce fallback geometry");
+
+    assert_eq!(err.kind(), io::ErrorKind::NotConnected);
+}
+
+#[test]
+fn missing_pixel_geometry_keeps_a_valid_terminal_grid() {
+    let reported_cell_size = AtomicU64::new(0);
+    let geometry = current_terminal_geometry_with(
+        true,
+        true,
+        &reported_cell_size,
+        Some((9, 18)),
+        None,
+        || Ok((80, 24)),
+    )
+    .expect("grid geometry remains valid without pixel dimensions");
+
+    assert_eq!(geometry, (80, 24, 9, 18, false));
+}
+
+#[test]
 fn direct_graphics_profile_is_narrow_and_transport_safe() {
     for (program, term, kitty, expected) in [
         ("ghostty", "", false, true),