0 介绍
视频地址：www.bilibili.com/video/BV1eg411g7c...
相关源码：github.com/anonymousGiga/Rust-and-...
1 说明
在上一节的实现中，我们是在Rust中实现了填充的内容，然后让wasm bindgen转换为一个有效的js字符串，这样就产生了不必要的副本。因为js代码已经知道宇宙的宽度和高度，因此可以直接读取构成cell的web assembly内存。另外我们将切换到Canvas API，而不是直接使用unicode文本。
本节直接上一节的内容之上进行修改。
2 实现
在wasm-game-of-life/www/index.html中的body标签内容修改为如下：
| <body> | |
| <!--canvas标签是表示图像或图表--> | |
| <canvas id="game-of-life-canvas"></canvas> | |
| <script src='./bootstrap.js'></script> | |
| </body> |
接下来，我们在wasm-game-of-life/src/lib.rs中添加如下代码：
| fn main() { | |
| /// Public methods, exported to JavaScript. | |
| impl Universe { | |
| // ... | |
| pub fn width(&self) -> u32 { | |
| self.width | |
| } | |
| pub fn height(&self) -> u32 { | |
| self.height | |
| } | |
| pub fn cells(&self) -> *const Cell { | |
| self.cells.as_ptr() | |
| } | |
| } | |
| } |
修改wasm-game-of-life/www/index.js中的代码如下：
| //import { Universe } from "wasm-game-of-life"; | |
| import { Universe, Cell } from "wasm-game-of-life"; | |
| import { memory } from "wasm-game-of-life/wasm_game_of_life_bg"; | |
| const CELL_SIZE = 5; // px | |
| const GRID_COLOR = "#CCCCCC"; | |
| const DEAD_COLOR = "#FFFFFF"; | |
| const ALIVE_COLOR = "#000000"; | |
| const universe = Universe.new(); | |
| const width = universe.width(); | |
| const height = universe.height(); | |
| const canvas = document.getElementById("game-of-life-canvas"); | |
| canvas.height = (CELL_SIZE + 1) * height + 1; | |
| canvas.width = (CELL_SIZE + 1) * width + 1; | |
| const ctx = canvas.getContext('2d'); | |
| function renderLoop() { | |
| universe.tick(); | |
| drawGrid(); | |
| drawCells(); | |
| window.requestAnimationFrame(renderLoop); | |
| } | |
| function drawGrid() { | |
| ctx.beginPath(); | |
| ctx.strokeStyle = GRID_COLOR; | |
| // Vertical lines. | |
| for (let i = 0; i <= width; i++) { | |
| ctx.moveTo(i * (CELL_SIZE + 1) + 1, 0); | |
| ctx.lineTo(i * (CELL_SIZE + 1) + 1, (CELL_SIZE + 1) * height + 1); | |
| } | |
| // Horizontal lines. | |
| for (let j = 0; j <= height; j++) { | |
| ctx.moveTo(0, j * (CELL_SIZE + 1) + 1); | |
| ctx.lineTo((CELL_SIZE + 1) * width + 1, j * (CELL_SIZE + 1) + 1); | |
| } | |
| ctx.stroke(); | |
| } | |
| function getIndex(row, column) { | |
| return row * width + column; | |
| } | |
| function drawCells() { | |
| const cellsPtr = universe.cells(); | |
| const cells = new Uint8Array(memory.buffer, cellsPtr, width * height); | |
| ctx.beginPath(); | |
| for (let row = 0; row < height; row++) { | |
| for (let col = 0; col < width; col++) { | |
| const idx = getIndex(row, col); | |
| ctx.fillStyle = cells[idx] === Cell.Dead | |
| ? DEAD_COLOR | |
| : ALIVE_COLOR; | |
| ctx.fillRect( | |
| col * (CELL_SIZE + 1) + 1, | |
| row * (CELL_SIZE + 1) + 1, | |
| CELL_SIZE, | |
| CELL_SIZE | |
| ); | |
| } | |
| } | |
| ctx.stroke(); | |
| } | |
| window.requestAnimationFrame(renderLoop); |
3 编译运行
在wasm-game-of-life目录下执行：
wasm-pack build
编译rust代码。
在wasm-game-of-life/www目录下执行：
npm run start
在浏览器中输入：
127.0.0.1:8080