Add widget hello world example

examples/hello_world_widgets.rs

@@ -0,0 +1,51 @@
+use std::convert::Infallible;
+
+use crossterm::event::Event;
+use crossterm::style::{ContentStyle, Stylize};
+use toss::widgets::Text;
+use toss::{Styled, Terminal, Widget};
+
+fn widget() -> impl Widget<Infallible> {
+    Text::new(
+        Styled::new("Hello world!", ContentStyle::default().green())
+            .then_plain("\n")
+            .then(
+                "Press any key to exit",
+                ContentStyle::default().on_dark_blue(),
+            ),
+    )
+}
+
+fn render_frame(term: &mut Terminal) {
+    loop {
+        // Must be called before rendering, otherwise the terminal has out-of-date
+        // size information and will present garbage.
+        term.autoresize().unwrap();
+
+        widget().draw(term.frame()).unwrap();
+        term.present().unwrap();
+
+        if term.measuring_required() {
+            term.measure_widths().unwrap();
+        } else {
+            break;
+        }
+    }
+}
+
+fn main() {
+    // Automatically enters alternate screen and enables raw mode
+    let mut term = Terminal::new().unwrap();
+    term.set_measuring(true);
+
+    loop {
+        // Render and display a frame. A full frame is displayed on the terminal
+        // once this function exits.
+        render_frame(&mut term);
+
+        // Exit if the user presses any buttons
+        if !matches!(crossterm::event::read().unwrap(), Event::Resize(_, _)) {
+            break;
+        }
+    }
+}