解決方案

src ├── main.rs ├── widgets │   ├── button.rs │   ├── label.rs │   └── window.rs └── widgets.rs
// ---- src/widgets.rs ---- mod button; mod label; mod window; pub trait Widget { /// Natural width of `self`. fn width(&self) -> usize; /// Draw the widget into a buffer. fn draw_into(&self, buffer: &mut dyn std::fmt::Write); /// Draw the widget on standard output. fn draw(&self) { let mut buffer = String::new(); self.draw_into(&mut buffer); println!("{buffer}"); } } pub use button::Button; pub use label::Label; pub use window::Window;
// ---- src/widgets/label.rs ---- use super::Widget; pub struct Label { label: String, } impl Label { pub fn new(label: &str) -> Label { Label { label: label.to_owned() } } } impl Widget for Label { fn width(&self) -> usize { // ANCHOR_END: Label-width self.label.lines().map(|line| line.chars().count()).max().unwrap_or(0) } // ANCHOR: Label-draw_into fn draw_into(&self, buffer: &mut dyn std::fmt::Write) { // ANCHOR_END: Label-draw_into writeln!(buffer, "{}", &self.label).unwrap(); } }
// ---- src/widgets/button.rs ---- use super::{Label, Widget}; pub struct Button { label: Label, } impl Button { pub fn new(label: &str) -> Button { Button { label: Label::new(label) } } } impl Widget for Button { fn width(&self) -> usize { // ANCHOR_END: Button-width self.label.width() + 8 // add a bit of padding } // ANCHOR: Button-draw_into fn draw_into(&self, buffer: &mut dyn std::fmt::Write) { // ANCHOR_END: Button-draw_into let width = self.width(); let mut label = String::new(); self.label.draw_into(&mut label); writeln!(buffer, "+{:-<width$}+", "").unwrap(); for line in label.lines() { writeln!(buffer, "|{:^width$}|", &line).unwrap(); } writeln!(buffer, "+{:-<width$}+", "").unwrap(); } }
// ---- src/widgets/window.rs ---- use super::Widget; pub struct Window { title: String, widgets: Vec<Box<dyn Widget>>, } impl Window { pub fn new(title: &str) -> Window { Window { title: title.to_owned(), widgets: Vec::new() } } pub fn add_widget(&mut self, widget: Box<dyn Widget>) { self.widgets.push(widget); } fn inner_width(&self) -> usize { std::cmp::max( self.title.chars().count(), self.widgets.iter().map(|w| w.width()).max().unwrap_or(0), ) } } impl Widget for Window { fn width(&self) -> usize { // ANCHOR_END: Window-width // Add 4 paddings for borders self.inner_width() + 4 } // ANCHOR: Window-draw_into fn draw_into(&self, buffer: &mut dyn std::fmt::Write) { // ANCHOR_END: Window-draw_into let mut inner = String::new(); for widget in &self.widgets { widget.draw_into(&mut inner); } let inner_width = self.inner_width(); // TODO: after learning about error handling, you can change // draw_into to return Result<(), std::fmt::Error>. Then use // the ?-operator here instead of .unwrap(). writeln!(buffer, "+-{:-<inner_width$}-+", "").unwrap(); writeln!(buffer, "| {:^inner_width$} |", &self.title).unwrap(); writeln!(buffer, "+={:=<inner_width$}=+", "").unwrap(); for line in inner.lines() { writeln!(buffer, "| {:inner_width$} |", line).unwrap(); } writeln!(buffer, "+-{:-<inner_width$}-+", "").unwrap(); } }
// ---- src/main.rs ---- mod widgets; use widgets::Widget; fn main() { let mut window = widgets::Window::new("Rust GUI Demo 1.23"); window .add_widget(Box::new(widgets::Label::new("This is a small text GUI demo."))); window.add_widget(Box::new(widgets::Button::new("Click me!"))); window.draw(); }