查看完整源代码 或 在线查看编译后的示例

使用 2D 画布 API 绘制一个笑脸。这是对 MDN 教程 的一部分移植到 web-sys。

Cargo.toml 启用了查询 DOM 和使用 2D 画布所需的特性。

[package]
name = "canvas"
version = "0.1.0"
authors = ["The wasm-bindgen Developers"]
edition = "2018"
rust-version = "1.57"

[lib]
crate-type = ["cdylib"]

[dependencies]
js-sys = "0.3.69"
wasm-bindgen = "0.2.92"

[dependencies.web-sys]
version = "0.3.4"
features = [
  'CanvasRenderingContext2d',
  'Document',
  'Element',
  'HtmlCanvasElement',
  'Window',
]

获取 <canvas> 元素，创建 2D 渲染上下文，并绘制笑脸。

# #![allow(unused_variables)]
#fn main() {
use std::f64;
use wasm_bindgen::prelude::*;

#[wasm_bindgen(start)]
fn start() {
    let document = web_sys::window().unwrap().document().unwrap();
    let canvas = document.get_element_by_id("canvas").unwrap();
    let canvas: web_sys::HtmlCanvasElement = canvas
        .dyn_into::<web_sys::HtmlCanvasElement>()
        .map_err(|_| ())
        .unwrap();

    let context = canvas
        .get_context("2d")
        .unwrap()
        .unwrap()
        .dyn_into::<web_sys::CanvasRenderingContext2d>()
        .unwrap();

    context.begin_path();

    // Draw the outer circle.
    context
        .arc(75.0, 75.0, 50.0, 0.0, f64::consts::PI * 2.0)
        .unwrap();

    // Draw the mouth.
    context.move_to(110.0, 75.0);
    context.arc(75.0, 75.0, 35.0, 0.0, f64::consts::PI).unwrap();

    // Draw the left eye.
    context.move_to(65.0, 65.0);
    context
        .arc(60.0, 65.0, 5.0, 0.0, f64::consts::PI * 2.0)
        .unwrap();

    // Draw the right eye.
    context.move_to(95.0, 65.0);
    context
        .arc(90.0, 65.0, 5.0, 0.0, f64::consts::PI * 2.0)
        .unwrap();

    context.stroke();
}

#}