chore(examples): refactor some examples (#578)

* chore(examples): Simplify timeout calculation with `Duration::saturating_sub`

Signed-off-by: rhysd <lin90162@yahoo.co.jp>

* fix(examples): Do not ignore errors from `poll_input` call

Signed-off-by: rhysd <lin90162@yahoo.co.jp>

---------

Signed-off-by: rhysd <lin90162@yahoo.co.jp>

examples/barchart.rs

@@ -119,9 +119,7 @@ fn run_app<B: Backend>(
     loop {
         terminal.draw(|f| ui(f, &app))?;
 
-        let timeout = tick_rate
-            .checked_sub(last_tick.elapsed())
-            .unwrap_or_else(|| Duration::from_secs(0));
+        let timeout = tick_rate.saturating_sub(last_tick.elapsed());
         if crossterm::event::poll(timeout)? {
             if let Event::Key(key) = event::read()? {
                 if let KeyCode::Char('q') = key.code {

examples/chart.rs

@@ -125,9 +125,7 @@ fn run_app<B: Backend>(
     loop {
         terminal.draw(|f| ui(f, &app))?;
 
-        let timeout = tick_rate
-            .checked_sub(last_tick.elapsed())
-            .unwrap_or_else(|| Duration::from_secs(0));
+        let timeout = tick_rate.saturating_sub(last_tick.elapsed());
         if crossterm::event::poll(timeout)? {
             if let Event::Key(key) = event::read()? {
                 if let KeyCode::Char('q') = key.code {

examples/demo/crossterm.rs

@@ -50,9 +50,7 @@ fn run_app<B: Backend>(
     loop {
         terminal.draw(|f| ui::draw(f, &mut app))?;
 
-        let timeout = tick_rate
-            .checked_sub(last_tick.elapsed())
-            .unwrap_or_else(|| Duration::from_secs(0));
+        let timeout = tick_rate.saturating_sub(last_tick.elapsed());
         if crossterm::event::poll(timeout)? {
             if let Event::Key(key) = event::read()? {
                 if key.kind == KeyEventKind::Press {

examples/demo/termwiz.rs

@@ -1,6 +1,5 @@
 use std::{
     error::Error,
-    io,
     time::{Duration, Instant},
 };
 
@@ -32,19 +31,17 @@ fn run_app(
     terminal: &mut Terminal<TermwizBackend>,
     mut app: App,
     tick_rate: Duration,
-) -> io::Result<()> {
+) -> Result<(), Box<dyn Error>> {
     let mut last_tick = Instant::now();
     loop {
         terminal.draw(|f| ui::draw(f, &mut app))?;
 
-        let timeout = tick_rate
-            .checked_sub(last_tick.elapsed())
-            .unwrap_or_else(|| Duration::from_secs(0));
-        if let Ok(Some(input)) = terminal
+        let timeout = tick_rate.saturating_sub(last_tick.elapsed());
+        if let Some(input) = terminal
             .backend_mut()
             .buffered_terminal_mut()
             .terminal()
-            .poll_input(Some(timeout))
+            .poll_input(Some(timeout))?
         {
             match input {
                 InputEvent::Key(key_code) => match key_code.key {

examples/inline.rs

@@ -98,9 +98,7 @@ fn input_handling(tx: mpsc::Sender<Event>) {
         let mut last_tick = Instant::now();
         loop {
             // poll for tick rate duration, if no events, sent tick event.
-            let timeout = tick_rate
-                .checked_sub(last_tick.elapsed())
-                .unwrap_or_else(|| Duration::from_secs(0));
+            let timeout = tick_rate.saturating_sub(last_tick.elapsed());
             if crossterm::event::poll(timeout).unwrap() {
                 match crossterm::event::read().unwrap() {
                     crossterm::event::Event::Key(key) => tx.send(Event::Input(key)).unwrap(),

examples/list.rs

@@ -175,9 +175,7 @@ fn run_app<B: Backend>(
     loop {
         terminal.draw(|f| ui(f, &mut app))?;
 
-        let timeout = tick_rate
-            .checked_sub(last_tick.elapsed())
-            .unwrap_or_else(|| Duration::from_secs(0));
+        let timeout = tick_rate.saturating_sub(last_tick.elapsed());
         if crossterm::event::poll(timeout)? {
             if let Event::Key(key) = event::read()? {
                 if key.kind == KeyEventKind::Press {

examples/paragraph.rs

@@ -64,9 +64,7 @@ fn run_app<B: Backend>(
     loop {
         terminal.draw(|f| ui(f, &app))?;
 
-        let timeout = tick_rate
-            .checked_sub(last_tick.elapsed())
-            .unwrap_or_else(|| Duration::from_secs(0));
+        let timeout = tick_rate.saturating_sub(last_tick.elapsed());
         if crossterm::event::poll(timeout)? {
             if let Event::Key(key) = event::read()? {
                 if let KeyCode::Char('q') = key.code {

examples/scrollbar.rs

@@ -57,9 +57,7 @@ fn run_app<B: Backend>(
     loop {
         terminal.draw(|f| ui(f, &mut app))?;
 
-        let timeout = tick_rate
-            .checked_sub(last_tick.elapsed())
-            .unwrap_or_else(|| Duration::from_secs(0));
+        let timeout = tick_rate.saturating_sub(last_tick.elapsed());
         if crossterm::event::poll(timeout)? {
             if let Event::Key(key) = event::read()? {
                 match key.code {

examples/sparkline.rs

@@ -109,9 +109,7 @@ fn run_app<B: Backend>(
     loop {
         terminal.draw(|f| ui(f, &app))?;
 
-        let timeout = tick_rate
-            .checked_sub(last_tick.elapsed())
-            .unwrap_or_else(|| Duration::from_secs(0));
+        let timeout = tick_rate.saturating_sub(last_tick.elapsed());
         if crossterm::event::poll(timeout)? {
             if let Event::Key(key) = event::read()? {
                 if let KeyCode::Char('q') = key.code {