feat(fmt): end VT output with its trailing rows, and replay soft wraps

crates/libghostty-vt-sys/build.rs

@@ -4,7 +4,7 @@ use std::process::Command;
 
 /// Pinned ghostty commit. Update this to pull a newer version.
 const GHOSTTY_REPO: &str = "https://github.com/aislopware/ghostty.git";
-const GHOSTTY_COMMIT: &str = "d266f39d98a3d77e70adf7d9775d4e92d73a6e3d";
+const GHOSTTY_COMMIT: &str = "42c228683ccd28844f03e18a8f1da699a01f5359";
 
 /// File name of the static archive on Windows. Ghostty installs it under this
 /// name for every Windows ABI so it does not collide with `ghostty-vt.lib`,

crates/libghostty-vt-sys/src/bindings.rs

@@ -3556,8 +3556,10 @@ pub struct FormatterTerminalOptions {
     pub extra: FormatterTerminalExtra,
     #[doc = " Optional selection to restrict output to a range.\n  If NULL, the entire screen is formatted."]
     pub selection: *const Selection,
-    #[doc = " For VT, emit every row's prompt flag and every cell's semantic\n  content (OSC 133), so a replay into a fresh terminal restores them.\n  Rows with no text but a prompt flag are emitted too. No effect when\n  unwrap is set."]
+    #[doc = " For VT, emit every row's prompt flag and every cell's semantic\n  content (OSC 133), so a replay into a fresh terminal restores them.\n  Rows with no text but a prompt flag are emitted too."]
     pub semantic_prompt: bool,
+    #[doc = " For VT, end with the blank rows after the last one with text, as\n  newlines, so a replay into a fresh terminal of the same size has\n  every row that was formatted."]
+    pub trailing_rows: bool,
 }
 #[allow(clippy::unnecessary_operation, clippy::identity_op)]
 const _: () = {
@@ -3579,6 +3581,8 @@ const _: () = {
         [::std::mem::offset_of!(FormatterTerminalOptions, selection) - 48usize];
     ["Offset of field: FormatterTerminalOptions::semantic_prompt"]
         [::std::mem::offset_of!(FormatterTerminalOptions, semantic_prompt) - 56usize];
+    ["Offset of field: FormatterTerminalOptions::trailing_rows"]
+        [::std::mem::offset_of!(FormatterTerminalOptions, trailing_rows) - 57usize];
 };
 impl Default for FormatterTerminalOptions {
     fn default() -> Self {

crates/libghostty-vt/src/fmt.rs

@@ -47,7 +47,9 @@ impl<'t, 's> FormatterOptions<'t, 's> {
         self.inner.emit = value.into();
         self
     }
-    /// Specify whether to unwrap soft-wrapped lines.
+    /// Specify whether to unwrap soft-wrapped lines. VT output then leaves
+    /// a soft-wrapped row for a replaying terminal of the same width to
+    /// wrap itself.
     pub fn with_unwrap(mut self, value: bool) -> Self {
         self.inner.unwrap = value;
         self
@@ -60,11 +62,17 @@ impl<'t, 's> FormatterOptions<'t, 's> {
     /// Specify whether VT output carries every row's prompt flag and every
     /// cell's semantic content (OSC 133), so a replay into a fresh terminal
     /// restores them. Rows with no text but a prompt flag are emitted too.
-    /// No effect with [`with_unwrap`](Self::with_unwrap).
     pub fn with_semantic_prompt(mut self, value: bool) -> Self {
         self.inner.semantic_prompt = value;
         self
     }
+    /// Specify whether VT output ends with the blank rows after the last
+    /// one with text, so a replay into a fresh terminal of the same size
+    /// has every row: a screen with history keeps it whole.
+    pub fn with_trailing_rows(mut self, value: bool) -> Self {
+        self.inner.trailing_rows = value;
+        self
+    }
     /// Specify the selection to restrict output to a range.
     ///
     /// If a selection is not given, the formatter defaults to formatting
@@ -390,6 +398,20 @@ mod tests {
         assert!(!has(&vt(false)), "only when asked");
     }
 
+    #[test]
+    fn vt_output_ends_with_the_trailing_rows_when_asked() {
+        let mut terminal = Terminal::new(10, 4).unwrap();
+        terminal.vt_write(b"top\r\n\r\n");
+        let vt = |trailing| {
+            let options = FormatterOptions::new()
+                .with_format(Format::Vt)
+                .with_trailing_rows(trailing);
+            format_buf(&mut Formatter::new(&terminal, options).unwrap())
+        };
+        assert!(vt(true).ends_with(b"top\r\n\r\n\r\n"), "every row but the last ends");
+        assert_eq!(vt(false), b"top", "left out unless asked");
+    }
+
     #[test]
     fn writer_output_matches_buffer_output_in_every_format() {
         let mut terminal = Terminal::new(20, 3).unwrap();