diff --git a/Cargo.lock b/Cargo.lock
index 42fb097..be2a7de 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -2,6 +2,32 @@
 # It is not intended for manual editing.
 version = 3
 
+[[package]]
+name = "aho-corasick"
+version = "0.7.18"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "1e37cfd5e7657ada45f742d6e99ca5788580b5c529dc78faf11ece6dc702656f"
+dependencies = [
+ "memchr",
+]
+
+[[package]]
+name = "atty"
+version = "0.2.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d9b39be18770d11421cdb1b9947a45dd3f37e93092cbf377614828a319d5fee8"
+dependencies = [
+ "hermit-abi",
+ "libc",
+ "winapi",
+]
+
+[[package]]
+name = "autocfg"
+version = "1.0.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cdb031dd78e28731d87d56cc8ffef4a8f36ca26c38fe2de700543e627f8a464a"
+
 [[package]]
 name = "bitflags"
 version = "1.3.2"
@@ -14,6 +40,12 @@ version = "1.0.69"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "e70cc2f62c6ce1868963827bd677764c62d07c3d9a3e1fb1177ee1a9ab199eb2"
 
+[[package]]
+name = "cfg-if"
+version = "1.0.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "baf1de4339761588bc0619e3cbc0120ee582ebb74b53b4efbf79117bd2da40fd"
+
 [[package]]
 name = "cmake"
 version = "0.1.45"
@@ -24,10 +56,73 @@ dependencies = [
 ]
 
 [[package]]
-name = "fltk"
-version = "1.1.11"
+name = "crossbeam-channel"
+version = "0.5.1"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "471fefc1fc3e019d314d542637f5bf48bd72a678f5e9052167b9ac7bea7b0a38"
+checksum = "06ed27e177f16d65f0f0c22a213e17c696ace5dd64b14258b52f9417ccb52db4"
+dependencies = [
+ "cfg-if",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-deque"
+version = "0.8.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6455c0ca19f0d2fbf751b908d5c55c1f5cbc65e03c4225427254b46890bdde1e"
+dependencies = [
+ "cfg-if",
+ "crossbeam-epoch",
+ "crossbeam-utils",
+]
+
+[[package]]
+name = "crossbeam-epoch"
+version = "0.9.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "4ec02e091aa634e2c3ada4a392989e7c3116673ef0ac5b72232439094d73b7fd"
+dependencies = [
+ "cfg-if",
+ "crossbeam-utils",
+ "lazy_static",
+ "memoffset",
+ "scopeguard",
+]
+
+[[package]]
+name = "crossbeam-utils"
+version = "0.8.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d82cfc11ce7f2c3faef78d8a684447b40d503d9681acebed6cb728d45940c4db"
+dependencies = [
+ "cfg-if",
+ "lazy_static",
+]
+
+[[package]]
+name = "either"
+version = "1.6.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "e78d4f1cc4ae33bbfc157ed5d5a5ef3bc29227303d595861deb238fcec4e9457"
+
+[[package]]
+name = "env_logger"
+version = "0.9.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "0b2cf0344971ee6c64c31be0d530793fba457d322dfec2810c453d0ef228f9c3"
+dependencies = [
+ "atty",
+ "humantime",
+ "log",
+ "regex",
+ "termcolor",
+]
+
+[[package]]
+name = "fltk"
+version = "1.1.12"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "6bf356f493316a45a5b90b8d5db97c0fd9850b87ab19cc7f88b53ca5d01fd710"
 dependencies = [
  "bitflags",
  "fltk-derive",
@@ -39,9 +134,9 @@ dependencies = [
 
 [[package]]
 name = "fltk-derive"
-version = "1.1.11"
+version = "1.1.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "712f09c29760a17e14a2f0d08a36b78bab82d5fbb3b2c3e17f3420f239351364"
+checksum = "57ddbb2cb93484b56da41b80c1466bca2620b68b61847d5e7f999bda0782ab78"
 dependencies = [
  "quote",
  "syn",
@@ -49,14 +144,29 @@ dependencies = [
 
 [[package]]
 name = "fltk-sys"
-version = "1.1.11"
+version = "1.1.12"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "5cc5eabad4839df806d102049c44586233743cf6607e2d2829155bb9fe45775e"
+checksum = "ebe424d107ab6ef0a4b756295c259bb8cec6e610548d55481457309884d526d4"
 dependencies = [
  "cmake",
  "libc",
 ]
 
+[[package]]
+name = "hermit-abi"
+version = "0.1.19"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "62b467343b94ba476dcb2500d242dadbb39557df889310ac77c5d99100aaac33"
+dependencies = [
+ "libc",
+]
+
+[[package]]
+name = "humantime"
+version = "2.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "9a3a5bfb195931eeb336b2a7b4d761daec841b97f947d34394601737a7bba5e4"
+
 [[package]]
 name = "lazy_static"
 version = "1.4.0"
@@ -69,6 +179,15 @@ version = "0.2.100"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "a1fa8cddc8fbbee11227ef194b5317ed014b8acbf15139bd716a18ad3fe99ec5"
 
+[[package]]
+name = "log"
+version = "0.4.14"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "51b9bbe6c47d51fc3e1a9b945965946b4c44142ab8792c50835a980d362c2710"
+dependencies = [
+ "cfg-if",
+]
+
 [[package]]
 name = "malloc_buf"
 version = "0.0.6"
@@ -78,6 +197,31 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "memchr"
+version = "2.4.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "308cc39be01b73d0d18f82a0e7b2a3df85245f84af96fdddc5d202d27e47b86a"
+
+[[package]]
+name = "memoffset"
+version = "0.6.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "59accc507f1338036a0477ef61afdae33cde60840f4dfe481319ce3ad116ddf9"
+dependencies = [
+ "autocfg",
+]
+
+[[package]]
+name = "num_cpus"
+version = "1.13.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "05499f3756671c15885fee9034446956fff3f243d6077b91e5767df161f766b3"
+dependencies = [
+ "hermit-abi",
+ "libc",
+]
+
 [[package]]
 name = "objc"
 version = "0.2.7"
@@ -114,13 +258,64 @@ dependencies = [
  "libc",
 ]
 
+[[package]]
+name = "rayon"
+version = "1.5.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "c06aca804d41dbc8ba42dfd964f0d01334eceb64314b9ecf7c5fad5188a06d90"
+dependencies = [
+ "autocfg",
+ "crossbeam-deque",
+ "either",
+ "rayon-core",
+]
+
+[[package]]
+name = "rayon-core"
+version = "1.9.1"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d78120e2c850279833f1dd3582f730c4ab53ed95aeaaaa862a2a5c71b1656d8e"
+dependencies = [
+ "crossbeam-channel",
+ "crossbeam-deque",
+ "crossbeam-utils",
+ "lazy_static",
+ "num_cpus",
+]
+
+[[package]]
+name = "regex"
+version = "1.5.4"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d07a8629359eb56f1e2fb1652bb04212c072a87ba68546a04065d525673ac461"
+dependencies = [
+ "aho-corasick",
+ "memchr",
+ "regex-syntax",
+]
+
+[[package]]
+name = "regex-syntax"
+version = "0.6.25"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "f497285884f3fcff424ffc933e56d7cbca511def0c9831a7f9b5f6153e3cc89b"
+
 [[package]]
 name = "roftl"
 version = "0.1.0"
 dependencies = [
+ "env_logger",
  "fltk",
+ "log",
+ "rayon",
 ]
 
+[[package]]
+name = "scopeguard"
+version = "1.1.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "d29ab0c6d3fc0ee92fe66e2d99f700eab17a8d57d1c1d3b748380fb20baa78cd"
+
 [[package]]
 name = "syn"
 version = "1.0.75"
@@ -132,8 +327,48 @@ dependencies = [
  "unicode-xid",
 ]
 
+[[package]]
+name = "termcolor"
+version = "1.1.2"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "2dfed899f0eb03f32ee8c6a0aabdb8a7949659e3466561fc0adf54e26d88c5f4"
+dependencies = [
+ "winapi-util",
+]
+
 [[package]]
 name = "unicode-xid"
 version = "0.2.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
 checksum = "8ccb82d61f80a663efe1f787a51b16b5a51e3314d6ac365b08639f52387b33f3"
+
+[[package]]
+name = "winapi"
+version = "0.3.9"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "5c839a674fcd7a98952e593242ea400abe93992746761e38641405d28b00f419"
+dependencies = [
+ "winapi-i686-pc-windows-gnu",
+ "winapi-x86_64-pc-windows-gnu",
+]
+
+[[package]]
+name = "winapi-i686-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ac3b87c63620426dd9b991e5ce0329eff545bccbbb34f3be09ff6fb6ab51b7b6"
+
+[[package]]
+name = "winapi-util"
+version = "0.1.5"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "70ec6ce85bb158151cae5e5c87f95a8e97d2c0c4b001223f33a334e3ce5de178"
+dependencies = [
+ "winapi",
+]
+
+[[package]]
+name = "winapi-x86_64-pc-windows-gnu"
+version = "0.4.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "712e227841d057c1ee1cd2fb22fa7e5a5461ae8e48fa2ca79ec42cfc1931183f"
diff --git a/Cargo.toml b/Cargo.toml
index 0399283..8353c9d 100644
--- a/Cargo.toml
+++ b/Cargo.toml
@@ -6,4 +6,7 @@ edition = "2018"
 # See more keys and their definitions at https://doc.rust-lang.org/cargo/reference/manifest.html
 
 [dependencies]
-fltk = "^1.1"
\ No newline at end of file
+fltk = "1.1"
+log = "0.4"
+env_logger = "0.9.0"
+rayon = "1.5.1"
\ No newline at end of file
diff --git a/src/main.rs b/src/main.rs
index e7a11a9..22dcc36 100644
--- a/src/main.rs
+++ b/src/main.rs
@@ -1,3 +1,95 @@
-fn main() {
-    println!("Hello, world!");
+use log::{debug, info, trace, warn};
+use std::error::Error;
+
+mod roftl;
+mod ui;
+
+use roftl::{Action, Entry, Source};
+
+struct TestSource {
+    name: String,
+    entries: Vec<Entry>,
+}
+
+impl TestSource {
+    fn new(s: &str) -> Box<TestSource> {
+        let mut ts = Box::new(TestSource {
+            name: "Testsource".into(),
+            entries: vec![],
+        });
+
+        (1..1000).for_each(|i| {
+            ts.add_entry(
+                format! {"Test {} {}", i, s},
+                format! {"Test {} description", i},
+            );
+        });
+
+        ts
+    }
+
+    fn add_entry(&mut self, name: String, description: String) {
+        let id = self.entries.len();
+        self.entries.push(Entry {
+            name,
+            description,
+            source: self,
+            id: id as u32,
+        });
+    }
+}
+
+impl Source for TestSource {
+    fn name(&self) -> &str {
+        &self.name
+    }
+
+    fn entries(&self) -> Vec<Entry> {
+        self.entries.clone()
+    }
+
+    fn action(&self, entry: &Entry, action: Action) {
+        println!("Doing action {:?} for entry {}", action, entry.name)
+    }
+}
+
+fn main() -> Result<(), Box<dyn Error>> {
+    env_logger::init();
+
+    let mut roftl = roftl::Roftl::new();
+
+    roftl
+        .add_source(TestSource::new("ts1"))
+        .add_source(TestSource::new("ts2"));
+
+    roftl.source();
+
+    let mut app = ui::draw()?;
+
+    roftl
+        .narrow("")
+        .iter()
+        .for_each(|e| app.add_candidate((*e).clone()));
+
+    while app.wait() {
+        match app.events.recv() {
+            Some(ui::Event::CandidateSelect(entry)) => {
+                trace! {"Selected: {}", entry.name}
+                roftl.action(&entry, Action::Primary)
+            }
+
+            Some(ui::Event::InputUpdate) => {
+                trace! {"Input: {}", &app.get_input()}
+                app.clear_candidates();
+                roftl
+                    .narrow(&app.get_input())
+                    .iter()
+                    .for_each(|e| app.add_candidate((*e).clone()));
+            }
+
+            _ => {}
+        }
+    }
+
+    Ok(())
 }
diff --git a/src/roftl.rs b/src/roftl.rs
new file mode 100644
index 0000000..4a8b0d5
--- /dev/null
+++ b/src/roftl.rs
@@ -0,0 +1,63 @@
+use rayon::iter::{IntoParallelRefIterator, ParallelIterator};
+
+#[derive(Clone)]
+pub struct Entry {
+    pub name: String,
+    pub description: String,
+    pub source: *const dyn Source,
+    pub id: u32
+}
+
+unsafe impl Sync for Entry {}
+unsafe impl Send for Entry {}
+
+
+#[derive(Debug)]
+pub enum Action {
+    Primary,
+}
+
+pub trait Source: Send + Sync {
+    fn name(&self) -> &str;
+    fn entries(&self) -> Vec<Entry>;
+    fn action(&self, entry: &Entry, action: Action);
+}
+
+pub struct Roftl {
+    sources: Vec<Box<dyn Source>>,
+    entries: Vec<Entry>,
+}
+
+impl Roftl {
+    pub fn new() -> Roftl {
+        Roftl {
+            sources: vec![],
+            entries: vec![],
+        }
+    }
+
+    pub fn add_source(&mut self, source: Box<dyn Source>) -> &mut Roftl {
+        self.sources.push(source);
+        self
+    }
+
+    pub fn source(&mut self) {
+        self.entries = self
+            .sources
+            .par_iter()
+            .flat_map_iter(|s| s.entries())
+            .collect();
+    }
+
+    pub fn narrow(&self, input: &str) -> Vec<&Entry> {
+        self.entries.par_iter()
+            .filter(|e| e.name.starts_with(input))
+            .collect()
+    }
+
+    pub fn action(&self, entry: &Entry, action: Action) {
+        unsafe {
+            Source::action(&*entry.source, entry, action);
+        }
+    }
+}
diff --git a/src/ui.rs b/src/ui.rs
new file mode 100644
index 0000000..047ad9a
--- /dev/null
+++ b/src/ui.rs
@@ -0,0 +1,110 @@
+use std::ops::Deref;
+
+use fltk::enums::{CallbackTrigger, Font, FrameType};
+use fltk::group::{PackType, ScrollType};
+use fltk::output;
+use fltk::prelude::*;
+use fltk::{app, window, input, group};
+
+use super::roftl::Entry;
+
+#[derive(Clone)]
+pub enum Event {
+    InputUpdate,
+    CandidateSelect(Entry)
+}
+
+pub struct RoftlApp {
+    pub app: app::App,
+    pub events: app::Receiver::<Event>,
+
+    send: app::Sender<Event>,
+    input: input::Input,
+    candidates: group::Pack,
+    scroll: group::Scroll
+}
+
+impl RoftlApp {
+    pub fn add_candidate(&mut self, entry: Entry) {
+        let mut output = output::Output::default();
+        output.set_value(&entry.name);
+        output.set_frame(FrameType::FlatBox);
+        output.set_size(380,30);
+
+        let s = self.send.clone();
+        output.handle(move |_widget, ev: fltk::enums::Event| {
+            match ev {
+                fltk::enums::Event::Focus => {
+                    s.send(Event::CandidateSelect(entry.clone()));
+                    true
+                },
+
+                _ => false
+            }
+        });
+
+        self.candidates.add(&output);
+        self.scroll.redraw();
+    }
+
+    pub fn clear_candidates(&mut self) {
+        for i in 0..self.candidates.children() {
+            self.candidates.child(i).and_then(|c| {Some(WidgetBase::delete(c))});
+        }
+
+        self.scroll.redraw();
+    }
+
+    pub fn get_input(&self) -> String {
+        self.input.value().clone()
+    }
+}
+
+impl Deref for RoftlApp {
+    type Target = app::App;
+
+    fn deref(&self) -> &Self::Target {
+        &self.app
+    }
+}
+
+pub fn draw() -> Result<RoftlApp, FltkError> {
+
+    app::set_font(Font::Screen);
+
+    let app = app::App::default();
+
+    let mut window = window::Window::default()
+        .with_size(400, 300)
+        .center_screen();
+    window.set_border(false);
+
+    let pack = group::Pack::default()
+        .with_type(PackType::Vertical)
+        .with_size(400,40);
+
+    let mut input = input::Input::default()
+        .with_size(0,40);
+    input.set_trigger(CallbackTrigger::Changed);
+
+    let scroll = group::Scroll::default()
+        .with_size(400, 300-40)
+        .with_type(ScrollType::AlwaysOn);
+
+    let candidates = group::Pack::default()
+        .with_size(380, 300-40)
+        .center_of(&scroll);
+
+    candidates.end();
+    scroll.end();
+    pack.end();
+    window.end();
+
+    window.show();
+
+    let (s, r) = app::channel::<Event>();
+    input.emit(s.clone(), Event::InputUpdate);
+
+    Ok(RoftlApp{app, events: r, send: s, input, candidates, scroll})
+}
+