fix: repaint after transient terminal resizes

1 files changed, 52 insertions, 0 deletions

diff --git a/src/platform/mod.rs b/src/platform/mod.rs
index 9b763223..ba92ca63 100644
--- a/src/platform/mod.rs
+++ b/src/platform/mod.rs
@@ -78,6 +78,45 @@ pub fn current_process_is_detached_server_daemon() -> bool {
     unsafe { libc::getsid(0) == libc::getpid() }
 }
 
+/// Raised by the SIGWINCH handler, consumed by the host resize watcher.
+#[cfg(unix)]
+static TERMINAL_RESIZE_SIGNALLED: std::sync::atomic::AtomicBool =
+    std::sync::atomic::AtomicBool::new(false);
+
+#[cfg(unix)]
+extern "C" fn record_terminal_resize_signal(_signal: libc::c_int) {
+    TERMINAL_RESIZE_SIGNALLED.store(true, std::sync::atomic::Ordering::Release);
+}
+
+/// Records SIGWINCH events that size polling can miss.
+#[cfg(unix)]
+pub(crate) fn watch_terminal_resize_signal() {
+    let mut action: libc::sigaction = unsafe { std::mem::zeroed() };
+    action.sa_sigaction =
+        record_terminal_resize_signal as extern "C" fn(libc::c_int) as libc::sighandler_t;
+    // Keep blocking stdin and socket reads from failing with EINTR.
+    action.sa_flags = libc::SA_RESTART;
+    unsafe {
+        libc::sigemptyset(&mut action.sa_mask);
+        libc::sigaction(libc::SIGWINCH, &action, std::ptr::null_mut());
+    }
+}
+
+#[cfg(not(unix))]
+pub(crate) fn watch_terminal_resize_signal() {}
+
+/// Returns whether a terminal size change was signalled since the last call.
+#[cfg(unix)]
+pub(crate) fn take_terminal_resize_signal() -> bool {
+    TERMINAL_RESIZE_SIGNALLED.swap(false, std::sync::atomic::Ordering::AcqRel)
+}
+
+/// Windows relies on size polling.
+#[cfg(not(unix))]
+pub(crate) fn take_terminal_resize_signal() -> bool {
+    false
+}
+
 #[cfg(unix)]
 #[derive(Debug, Clone, PartialEq, Eq)]
 pub struct ClipboardCommand {
@@ -313,6 +352,19 @@ mod tests {
     use super::*;
 
     #[test]
+    fn terminal_resize_signal_is_recorded_once_per_delivery() {
+        watch_terminal_resize_signal();
+        assert!(!take_terminal_resize_signal());
+
+        unsafe {
+            libc::raise(libc::SIGWINCH);
+        }
+
+        assert!(take_terminal_resize_signal());
+        assert!(!take_terminal_resize_signal());
+    }
+
+    #[test]
     fn pane_shell_process_names_reject_exec_replacement_programs() {
         for shell in ["bash", "-zsh", "/bin/fish", "pwsh", "powershell.exe"] {
             assert!(is_pane_shell_process_name(shell), "{shell}");