3.6.1 解答

Tue, 11 Aug 2026 11:30:00 +0800

译文 · 基于 Comprehensive Rust

原文链接: https://google.github.io/comprehensive-rust/modules/solution.html

3.6.1 解答

src
├── main.rs
├── widgets
│   ├── button.rs
│   ├── label.rs
│   └── window.rs
└── widgets.rs

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// Copyright 2023 Google LLC
// SPDX-License-Identifier: Apache-2.0
// ---- src/widgets.rs ----
pub use button::Button;
pub use label::Label;
pub use window::Window;

mod button;
mod label;
mod window;

pub trait Widget {
 /// `self` 的自然宽度。
 fn width(&self) -> usize;

 /// 将 widget 绘制到缓冲区。
 fn draw_into(&self, buffer: &mut dyn std::fmt::Write);

 /// 将 widget 绘制到标准输出。
 fn draw(&self) {
 let mut buffer = String::new();
 self.draw_into(&mut buffer);
 println!("{buffer}");
 }
}

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// Copyright 2023 Google LLC
// SPDX-License-Identifier: Apache-2.0
// ---- 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();
 }
}

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// Copyright 2023 Google LLC
// SPDX-License-Identifier: Apache-2.0
// ---- 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 // 稍微加点内边距
 }

 // 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();
 }
}

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// Copyright 2023 Google LLC
// SPDX-License-Identifier: Apache-2.0
// ---- 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
 // 为边框额外加 4 的内边距
 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: 学完错误处理后，可将 draw_into 改为返回
 // Result<(), std::fmt::Error>，然后在这里用 ? 运算符
 // 代替 .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();
 }
}

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// Copyright 2023 Google LLC
// SPDX-License-Identifier: Apache-2.0
// ---- src/main.rs ----
mod widgets;

use widgets::{Button, Label, Widget, Window};

fn main() {
 let mut window = Window::new("Rust GUI Demo 1.23");
 window.add_widget(Box::new(Label::new("This is a small text GUI demo.")));
 window.add_widget(Box::new(Button::new("Click me!")));
 window.draw();
}

3.6 练习：GUI 库的模块划分 on 编程那些事儿

3.6.1 解答

3.6.1 解答