fix: preserve styled blank rows in VT replay

src/config/io.zig

@@ -150,6 +150,30 @@ pub const ReadableIO = union(enum) {
         try v.formatEntry(formatterpkg.entryFormatter("a", &buf.writer));
         try std.testing.expectEqualSlices(u8, "a = raw:foo\n", buf.written());
     }
+
+    // The embedded apprt stores initial input as a Zig-escaped raw
+    // value, so parsing it must give back the exact input bytes.
+    test "cloneParsed restores Zig-escaped bytes" {
+        const testing = std.testing;
+        var arena = ArenaAllocator.init(testing.allocator);
+        defer arena.deinit();
+        const alloc = arena.allocator();
+
+        const inputs = [_][]const u8{
+            "printf '\x1b]0;라마바OSC테스트\x07'\r",
+            "日本語のタイトル",
+            "\u{1F680} \u{1F469}\u{200D}\u{1F469}\u{200D}\u{1F467}",
+            "e\u{301}cole \u{1112}\u{1161}\u{11AB}",
+            "invalid \xff\xfe\x80 bytes",
+        };
+        for (inputs) |input| {
+            var escaped: std.Io.Writer.Allocating = .init(alloc);
+            try std.zig.stringEscape(input, &escaped.writer);
+            const v: Self = .{ .raw = try escaped.toOwnedSliceSentinel(0) };
+            const parsed = try v.cloneParsed(alloc);
+            try testing.expectEqualSlices(u8, input, parsed.raw);
+        }
+    }
 };
 
 pub const RepeatableReadableIO = struct {

src/config/string.zig

@@ -20,16 +20,23 @@ pub fn parse(out: []u8, bytes: []const u8) ![]u8 {
             continue;
         }
 
+        // Zig's \xNN syntax represents a single byte, while the other
+        // escape sequences represent Unicode codepoints.
+        const is_byte_escape = src_i + 1 < bytes.len and
+            bytes[src_i + 1] == 'x';
+
         // Parse the escape sequence
         switch (std.zig.string_literal.parseEscapeSequence(
             bytes,
             &src_i,
         )) {
             .failure => return error.InvalidString,
-            .success => |cp| dst_i += try std.unicode.utf8Encode(
-                cp,
-                out[dst_i..],
-            ),
+            .success => |cp| if (is_byte_escape) {
+                out[dst_i] = @intCast(cp);
+                dst_i += 1;
+            } else {
+                dst_i += try std.unicode.utf8Encode(cp, out[dst_i..]);
+            },
         }
     }
 
@@ -100,6 +107,15 @@ test "parse: escapes" {
     }
 }
 
+test "parse: hex escapes are bytes" {
+    var buf: [128]u8 = undefined;
+    const result = try parse(
+        &buf,
+        "\\xe6\\x97\\xa5\\xe6\\x9c\\xac\\xe8\\xaa\\x9e",
+    );
+    try std.testing.expectEqualStrings("日本語", result);
+}
+
 test "codepointIterator: empty" {
     var it = codepointIterator("");
     try std.testing.expectEqual(null, try it.next());

src/terminal/formatter.zig

@@ -1143,9 +1143,15 @@ pub const PageFormatter = struct {
             };
 
             // If this row is blank, accumulate to avoid a bunch of extra
-            // work later. If it isn't blank, make sure we dump all our
-            // blanks.
-            if (!Cell.hasTextAny(cells_subset)) {
+            // work later. A styled blank row is content for styled output:
+            // dropping it loses full-width background bands during replay.
+            const has_styled_content = if (formatStyled(self.opts.emit)) styled: {
+                for (cells_subset) |cell| {
+                    if (!cell.isEmpty() or cell.hasStyling()) break :styled true;
+                }
+                break :styled false;
+            } else false;
+            if (!Cell.hasTextAny(cells_subset) and !has_styled_content) {
                 blank_rows += 1;
                 continue;
             }
@@ -6718,6 +6724,43 @@ test "Page VT background color on trailing blank cells" {
     try testing.expect(has_red_bg_line1);
 }
 
+test "Page VT preserves a fully styled blank row" {
+    const testing = std.testing;
+    const alloc = testing.allocator;
+    const io = testing.io;
+
+    var builder: std.Io.Writer.Allocating = .init(alloc);
+    defer builder.deinit();
+
+    var t = try Terminal.init(io, alloc, .{
+        .cols = 20,
+        .rows = 5,
+    });
+    defer t.deinit(alloc);
+
+    var s = t.vtStream();
+    defer s.deinit();
+    // Erase the complete first row with a background color and then put text
+    // on the next row. The first row has no text cells, but every cell carries
+    // the background style that a replay must preserve.
+    s.nextSlice("\x1b[41m\x1b[2K\x1b[0m\r\nline2");
+
+    const page = t.screens.active.pages.pages.last.?.page();
+    var opts: Options = .vt;
+    opts.trim = false;
+    var formatter: PageFormatter = .init(page, opts);
+    try formatter.format(&builder.writer);
+    const output = builder.writer.buffered();
+
+    const first_break = std.mem.indexOf(u8, output, "\r\n") orelse {
+        return error.TestUnexpectedResult;
+    };
+    // SGR 41 is stored as palette background 1, which the VT formatter
+    // writes in its indexed form.
+    try testing.expect(std.mem.indexOf(u8, output[0..first_break], "\x1b[48;5;1m") != null);
+    try testing.expectEqual(@as(usize, 20), std.mem.count(u8, output[0..first_break], " "));
+}
+
 test "Page HTML with hyperlinks" {
     const testing = std.testing;
     const alloc = testing.allocator;