Snippet from Ghostty source. https://mitchellh.com/

xtgettcap.zig

/// Returns a ComptimeStringMap for all of the capabilities in this terminfo.
/// The value is the value that should be sent as a response to XTGETTCAP.
/// Important: the value is the FULL response included the escape sequences.
pub fn xtgettcapMap(comptime self: Source) type {
    const KV = struct { []const u8, []const u8 };

    // We have all of our capabilities plus To, TN, and RGB which aren't
    // in the capabilities list but are query-able.
    const len = self.capabilities.len + 3;
    var kvs: [len]KV = .{.{ "", "" }} ** len;

    // We first build all of our entries with raw K=V pairs.
    kvs[0] = .{ "TN", self.names[0] };
    kvs[1] = .{ "Co", "256" };
    kvs[2] = .{ "RGB", "8" };
    for (self.capabilities, 3..) |cap, i| {
        kvs[i] = .{ cap.name, switch (cap.value) {
            .canceled => @compileError("canceled not handled yet"),
            .boolean => "",
            .string => |v| v,
            .numeric => |v| numeric: {
                var buf: [10]u8 = undefined;
                const num_len = std.fmt.formatIntBuf(&buf, v, 10, .upper, .{});
                break :numeric buf[0..num_len];
            },
        } };
    }

    // Now go through and convert them all to hex-encoded strings.
    for (&kvs) |*entry| {
        // The key is just the raw hex-encoded string
        entry[0] = hexencode(entry[0]);

        // The value is more complex
        var buf: [5 + entry[0].len + 1 + (entry[1].len * 2) + 2]u8 = undefined;
        entry[1] = if (std.mem.eql(u8, entry[1], "")) std.fmt.bufPrint(
            &buf,
            "\x1bP1+r{s}\x1b\\",
            .{entry[0]}, // important: hex-encoded name
        ) catch unreachable else std.fmt.bufPrint(
            &buf,
            "\x1bP1+r{s}={s}\x1b\\",
            .{ entry[0], hexencode(entry[1]) }, // important: hex-encoded name
        ) catch unreachable;
    }

    return std.ComptimeStringMap([]const u8, kvs);
}