feat(example): debounce, top right corner performance info and update on resize

examples/example.rs

@@ -1,6 +1,10 @@
+use std::time::{Duration, Instant};
+
 use crossterm::event::{Event, KeyCode, MouseEventKind};
 use ratatui::backend::{Backend, CrosstermBackend};
+use ratatui::layout::Rect;
 use ratatui::style::{Color, Modifier, Style};
+use ratatui::text::Span;
 use ratatui::widgets::{Block, Scrollbar, ScrollbarOrientation};
 use ratatui::{Frame, Terminal};
 use tui_tree_widget::{Tree, TreeItem, TreeState};
@@ -133,32 +137,72 @@ fn main() -> std::io::Result<()> {
 }
 
 fn run_app<B: Backend>(terminal: &mut Terminal<B>, mut app: App) -> std::io::Result<()> {
+    const DEBOUNCE: Duration = Duration::from_millis(20); // 50 FPS
+
+    let before = Instant::now();
     terminal.draw(|frame| app.draw(frame))?;
+    let mut last_render_took = before.elapsed();
+
+    let mut debounce: Option<Instant> = None;
+
     loop {
-        let update = match crossterm::event::read()? {
-            Event::Key(key) => match key.code {
-                KeyCode::Char('q') => return Ok(()),
-                KeyCode::Char('\n' | ' ') => app.state.toggle_selected(),
-                KeyCode::Left => app.state.key_left(),
-                KeyCode::Right => app.state.key_right(),
-                KeyCode::Down => app.state.key_down(),
-                KeyCode::Up => app.state.key_up(),
-                KeyCode::Esc => app.state.select(Vec::new()),
-                KeyCode::Home => app.state.select_first(),
-                KeyCode::End => app.state.select_last(),
-                KeyCode::PageDown => app.state.scroll_down(3),
-                KeyCode::PageUp => app.state.scroll_up(3),
+        let timeout = debounce.map_or(DEBOUNCE, |start| DEBOUNCE.saturating_sub(start.elapsed()));
+        if crossterm::event::poll(timeout)? {
+            let update = match crossterm::event::read()? {
+                Event::Key(key) => match key.code {
+                    KeyCode::Char('q') => return Ok(()),
+                    KeyCode::Char('\n' | ' ') => app.state.toggle_selected(),
+                    KeyCode::Left => app.state.key_left(),
+                    KeyCode::Right => app.state.key_right(),
+                    KeyCode::Down => app.state.key_down(),
+                    KeyCode::Up => app.state.key_up(),
+                    KeyCode::Esc => app.state.select(Vec::new()),
+                    KeyCode::Home => app.state.select_first(),
+                    KeyCode::End => app.state.select_last(),
+                    KeyCode::PageDown => app.state.scroll_down(3),
+                    KeyCode::PageUp => app.state.scroll_up(3),
+                    _ => false,
+                },
+                Event::Mouse(mouse) => match mouse.kind {
+                    MouseEventKind::ScrollDown => app.state.scroll_down(1),
+                    MouseEventKind::ScrollUp => app.state.scroll_up(1),
+                    _ => false,
+                },
+                Event::Resize(_, _) => true,
                 _ => false,
-            },
-            Event::Mouse(mouse) => match mouse.kind {
-                MouseEventKind::ScrollDown => app.state.scroll_down(1),
-                MouseEventKind::ScrollUp => app.state.scroll_up(1),
-                _ => false,
-            },
-            _ => false,
-        };
-        if update {
-            terminal.draw(|frame| app.draw(frame))?;
+            };
+            if update {
+                debounce.get_or_insert_with(Instant::now);
+            }
+        }
+        if debounce.is_some_and(|debounce| debounce.elapsed() > DEBOUNCE) {
+            let before = Instant::now();
+            terminal.draw(|frame| {
+                app.draw(frame);
+
+                // Performance info in top right corner
+                {
+                    let text = format!(
+                        " {} {last_render_took:?} {:.1} FPS",
+                        frame.count(),
+                        1.0 / last_render_took.as_secs_f64()
+                    );
+                    #[allow(clippy::cast_possible_truncation)]
+                    let area = Rect {
+                        y: 0,
+                        height: 1,
+                        x: frame.size().width.saturating_sub(text.len() as u16),
+                        width: text.len() as u16,
+                    };
+                    frame.render_widget(
+                        Span::styled(text, Style::new().fg(Color::Black).bg(Color::Gray)),
+                        area,
+                    );
+                }
+            })?;
+            last_render_took = before.elapsed();
+
+            debounce = None;
         }
     }
 }