diff --git a/Cargo.lock b/Cargo.lock
index 6acfe1c..163ba9c 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -1757,9 +1757,9 @@ dependencies = [
 
 [[package]]
 name = "proc-macro2"
-version = "1.0.52"
+version = "1.0.53"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1d0e1ae9e836cc3beddd63db0df682593d7e2d3d891ae8c9083d2113e1744224"
+checksum = "ba466839c78239c09faf015484e5cc04860f88242cff4d03eb038f04b4699b73"
 dependencies = [
  "unicode-ident",
 ]
@@ -1984,22 +1984,22 @@ dependencies = [
 
 [[package]]
 name = "serde"
-version = "1.0.156"
+version = "1.0.158"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "314b5b092c0ade17c00142951e50ced110ec27cea304b1037c6969246c2469a4"
+checksum = "771d4d9c4163ee138805e12c710dd365e4f44be8be0503cb1bb9eb989425d9c9"
 dependencies = [
  "serde_derive",
 ]
 
 [[package]]
 name = "serde_derive"
-version = "1.0.156"
+version = "1.0.158"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d7e29c4601e36bcec74a223228dce795f4cd3616341a4af93520ca1a837c087d"
+checksum = "e801c1712f48475582b7696ac71e0ca34ebb30e09338425384269d9717c62cad"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 1.0.109",
+ "syn 2.0.8",
 ]
 
 [[package]]
@@ -2153,9 +2153,9 @@ dependencies = [
 
 [[package]]
 name = "syn"
-version = "2.0.6"
+version = "2.0.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "ece519cfaf36269ea69d16c363fa1d59ceba8296bbfbfc003c3176d01f2816ee"
+checksum = "bcc02725fd69ab9f26eab07fad303e2497fad6fb9eba4f96c4d1687bdf704ad9"
 dependencies = [
  "proc-macro2",
  "quote",
@@ -2200,7 +2200,7 @@ checksum = "f9456a42c5b0d803c8cd86e73dd7cc9edd429499f37a3550d286d5e86720569f"
 dependencies = [
  "proc-macro2",
  "quote",
- "syn 2.0.6",
+ "syn 2.0.8",
 ]
 
 [[package]]
@@ -2256,9 +2256,9 @@ checksum = "3ab8ed2edee10b50132aed5f331333428b011c99402b5a534154ed15746f9622"
 
 [[package]]
 name = "toml_edit"
-version = "0.19.7"
+version = "0.19.8"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "dc18466501acd8ac6a3f615dd29a3438f8ca6bb3b19537138b3106e575621274"
+checksum = "239410c8609e8125456927e6707163a3b1fdb40561e4b803bc041f466ccfdc13"
 dependencies = [
  "indexmap",
  "toml_datetime",
@@ -2825,9 +2825,9 @@ dependencies = [
 
 [[package]]
 name = "winnow"
-version = "0.3.6"
+version = "0.4.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "23d020b441f92996c80d94ae9166e8501e59c7bb56121189dc9eab3bd8216966"
+checksum = "deac0939bd6e4f24ab5919fbf751c97a8cfc8543bb083a305ed5c0c10bb241d1"
 dependencies = [
  "memchr",
 ]
diff --git a/src/.engine.rs.swp b/src/.engine.rs.swp
new file mode 100644
index 0000000..ec956c9
Binary files /dev/null and b/src/.engine.rs.swp differ
diff --git a/src/.gui.rs.swp b/src/.gui.rs.swp
deleted file mode 100644
index 0526f43..0000000
Binary files a/src/.gui.rs.swp and /dev/null differ
diff --git a/src/engine.rs b/src/engine.rs
index 84b3459..ab92677 100644
--- a/src/engine.rs
+++ b/src/engine.rs
@@ -8,24 +8,30 @@ pub trait InputEngine {
    fn get(&mut self) -> Vec<char>;
 }
 
-pub fn build_input_engine(cfg: &Engine) -> Result<Box<dyn InputEngine>, String> {
+pub fn build_input_engine(cfg: &Engine) -> impl InputEngine {
    match cfg.name.as_str() {
-      "stdin" => return Ok(Box::new(InputEngineStdin{})),
-      "kafka" => return build_input_engine_kafka(&cfg),
-      "udp" => return build_input_engine_udp(&cfg),
-      "device" => return build_input_engine_device(&cfg),
-      _ => return Err("unknown input engine name".to_string() + &cfg.name),
-   }
+      "stdin" => {
+         return InputEngineStdin{};
+      },
+      "kafka" => {
+         return build_input_engine_kafka(&cfg).unwrap();
+      },
+      "udp" => return build_input_engine_udp(&cfg).unwrap(),
+      "device" => return build_input_engine_device(&cfg).unwrap(),
+      _ => {},
+   };
+   assert!(false);
+   InputEngineStdin{}
 }
 
 struct InputEngineDevice {
 }
 
-pub fn build_input_engine_device(cfg: &Engine) -> Result<Box<dyn InputEngine>, String> {
+pub fn build_input_engine_device(cfg: &Engine) -> Result<InputEngineDevice, String> {
    return build_input_engine_device_gilrs(cfg)
 }
 
-pub fn build_input_engine_device_gilrs(cfg: &Engine) -> Result<Box<dyn InputEngine>, String> {
+pub fn build_input_engine_device_gilrs(cfg: &Engine) -> Result<InputEngineDevice, String> {
    let _device_cfg = cfg.device.as_ref().unwrap();
 
    let mut gilrs = Gilrs::new().unwrap();
@@ -59,7 +65,7 @@ pub fn build_input_engine_device_gilrs(cfg: &Engine) -> Result<Box<dyn InputEngi
    return Err("do what".to_string());
 }
 
-pub fn build_input_engine_device_hidapi(cfg: &Engine) -> Result<Box<dyn InputEngine>, String> {
+pub fn build_input_engine_device_hidapi(cfg: &Engine) -> Result<InputEngineDevice, String> {
    let _device_cfg = cfg.device.as_ref().unwrap();
 
    match HidApi::new() {
@@ -75,7 +81,7 @@ pub fn build_input_engine_device_hidapi(cfg: &Engine) -> Result<Box<dyn InputEng
    return Err("do what".to_string());
 }
 
-pub fn build_input_engine_device_rusb(cfg: &Engine) -> Result<Box<dyn InputEngine>, String> {
+pub fn build_input_engine_device_rusb(cfg: &Engine) -> Result<InputEngineDevice, String> {
    let _device_cfg = cfg.device.as_ref().unwrap();
 
    assert!(rusb::has_capability());
@@ -105,12 +111,12 @@ struct InputEngineUDP {
    port: i32,
 }
 
-pub fn build_input_engine_udp(cfg: &Engine) -> Result<Box<dyn InputEngine>, String> {
+pub fn build_input_engine_udp(cfg: &Engine) -> Result<InputEngineUDP, String> {
    let udp_cfg = cfg.udp.as_ref().unwrap();
-   return Ok(Box::new(InputEngineUDP{
+   return Ok(InputEngineUDP{
       last_socket: None,
       port: udp_cfg.port,
-   }));
+   });
 }
 
 impl InputEngine for InputEngineUDP {
@@ -137,7 +143,7 @@ impl InputEngine for InputEngineUDP {
 struct InputEngineKafka {
 }
 
-pub fn build_input_engine_kafka(cfg: &Engine) -> Result<Box<dyn InputEngine>, String> {
+pub fn build_input_engine_kafka(cfg: &Engine) -> Result<InputEngineKafka, String> {
    let _kafka_cfg = cfg.kafka.as_ref().unwrap();
    return Err("do what".to_string());
 }
@@ -185,12 +191,14 @@ pub trait OutputEngine {
    fn put(&mut self, v: Vec<char>);
 }
 
-pub fn build_output_engine(cfg: &Engine) -> Result<Box<dyn OutputEngine>, String> {
-   match cfg.name.as_str() {
-      "stdout" => return Ok(Box::new(OutputEngineStdout{})),
-      "udp" => return build_output_engine_udp(&cfg),
-      _ => return Err("unknown output engine name".to_string() + &cfg.name),
+pub fn build_output_engine(cfg: &Engine) -> impl OutputEngine {
+   if cfg.name.as_str() == "stdout" {
+      return OutputEngineStdout{};
+   } else if cfg.name.as_str() == "udp" {
+      return build_output_engine_udp(&cfg).unwrap();
    }
+   assert!(false);
+   OutputEngineStdout{}
 }
 
 struct OutputEngineStdout {}
@@ -228,13 +236,13 @@ struct OutputEngineUDP {
    port: i32,
 }
 
-pub fn build_output_engine_udp(cfg: &Engine) -> Result<Box<dyn OutputEngine>, String> {
+pub fn build_output_engine_udp(cfg: &Engine) -> Result<OutputEngineUDP, String> {
    let udp_cfg = cfg.udp.as_ref().unwrap();
-   return Ok(Box::new(OutputEngineUDP{
+   return Ok(OutputEngineUDP{
       last_socket: None,
       host: udp_cfg.host.clone().unwrap(),
       port: udp_cfg.port,
-   }));
+   });
 }
 
 impl OutputEngine for OutputEngineUDP {
diff --git a/src/gui.rs b/src/gui.rs
index 177caf0..2c4241a 100644
--- a/src/gui.rs
+++ b/src/gui.rs
@@ -5,10 +5,12 @@ use iced::event;
 use iced::subscription;
 use iced::{Alignment, Element, Application, Settings, Subscription, Theme, Command};
 
-pub fn main(outputEngine: dyn FnMut(Vec<char>)) -> iced::Result {
+use crate::engine::OutputEngine;
+
+pub fn main(outputEngine: &impl OutputEngine) -> iced::Result {
    let settings = Settings{
       flags: Flags {
-         outputEngine: outputEngine,
+         //outputEngine: outputEngine,
       },
       ..Settings::<Flags>::default()
    };
@@ -24,7 +26,7 @@ struct Main {
 
 #[derive(Default)]
 struct Flags {
-   outputEngine: dyn FnMut(Vec<char>),
+   //outputEngine: impl OutputEngine,
 }
 
 struct Inputs {
diff --git a/src/main.rs b/src/main.rs
index 820ff31..2d25dc0 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -2,25 +2,21 @@ mod config;
 mod engine;
 mod gui;
 
+use crate::engine::{InputEngine, OutputEngine};
+
 fn main() {
    let cfg = config::build_config().unwrap();
    if cfg.streams.input.engine.name == "gui" {
-      let output_engine = engine::build_output_engine(&cfg.streams.output.engine);
-      let mut output_engine = output_engine.unwrap();
-      let cb = |v: Vec<char>| output_engine.put(v);
-      gui::main(cb).unwrap();
+      let mut output_engine = engine::build_output_engine(&cfg.streams.output.engine);
+      gui::main(&output_engine).unwrap();
    } else {
       main_cli(cfg);
    }
 }
 
 fn main_cli(cfg: config::Config) {
-   let input_engine = engine::build_input_engine(&cfg.streams.input.engine);
-   let output_engine = engine::build_output_engine(&cfg.streams.output.engine);
-   println!("{:?} => {}", cfg.streams.input.engine.name, input_engine.is_ok());
-   println!("{:?} => {}", cfg.streams.output.engine.name, output_engine.is_ok());
-   let mut input_engine = input_engine.unwrap();
-   let mut output_engine = output_engine.unwrap();
+   let mut input_engine = engine::build_input_engine(&cfg.streams.input.engine);
+   let mut output_engine = engine::build_output_engine(&cfg.streams.output.engine);
    loop {
       output_engine.put(input_engine.get());
    }