zigzag/index.html at main · ibebrett/zigzag · GitHub

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<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8" />
    <title>ZigZag</title>
  </head>
  <body>
    <p>The buttons are a, s and the arrow keys.</p>
    <canvas id="canvas" width="512" height="512"></canvas>
    <script>
      class FPSCounter {
        init() {
          this.last = 0;
        }

        tick() {
          const now = Date.now();
          const diff = now - this.last;
          this.last = now;
          return diff;
        }
      }

      const newInputState = () => ({
        a_pressed: false,
        b_pressed: false,
        up_pressed: false,
        down_pressed: false,
        left_pressed: false,
        right_pressed: false,
      });

      (async () => {
        const canvas = document.getElementById("canvas");
        const ctx = canvas.getContext("2d");
        ctx.imageSmoothingEnabled = false;
        ctx.scale(4, 4);

        const img = await new Promise((resolve) => {
          const img = new Image(); // Create new img element
          img.src = "assets/sprites.png"; // Set source path

          img.addEventListener(
            "load",
            () => {
              resolve(img);
            },
            false
          );
        });

        const wasmPromise = new Promise((resolve) => {
          const importObject = {
            module: {},
            env: {
              memory: new WebAssembly.Memory({ initial: 256 }),
              consoleLog: () => {},
              wasmSprite: (dx, dy, dw, dh, sx, sy, sw, sh) => {
                // Don't draw the image if its off screen.
                ctx.drawImage(img, sx, sy, sw, sh, dx, dy, dw, dh);
              },
            },
          };
          fetch("zig-out/lib/wasm.wasm")
            .then((response) => response.arrayBuffer())
            .then((bytes) => WebAssembly.instantiate(bytes, importObject))
            .then((results) => {
              resolve(results);
            });
        });

        const wasm = await wasmPromise;

        const exports = wasm.instance.exports;
        exports.setup();

        // Setup the keyboard
        const inputState = {
          a_pressed: false,
          b_pressed: false,
          up_pressed: false,
          down_pressed: false,
          left_pressed: false,
          right_pressed: false,

          a_down: false,
          b_down: false,
          up_down: false,
          down_down: false,
          left_down: false,
          right_down: false,
        };

        document.addEventListener("keydown", (e) => {
          if (e.key === "a") {
            inputState.a_pressed = true;
            inputState.a_down = true;
          }
          if (e.key === "s") {
            inputState.b_pressed = true;
            inputState.b_down = true;
          }
          if (e.key === "ArrowDown") {
            inputState.down_pressed = true;
            inputState.down_down = true;
          }
          if (e.key === "ArrowUp") {
            inputState.up_pressed = true;
            inputState.up_down = true;
          }
          if (e.key === "ArrowLeft") {
            inputState.left_pressed = true;
            inputState.left_down = true;
          }
          if (e.key === "ArrowRight") {
            inputState.right_pressed = true;
            inputState.right_down = true;
          }
        });

        document.addEventListener("keyup", (e) => {
          if (e.key === "a") {
            inputState.a_down = false;
          }
          if (e.key === "s") {
            inputState.b_down = false;
          }
          if (e.key === "ArrowDown") {
            inputState.down_down = false;
          }
          if (e.key === "ArrowUp") {
            inputState.up_down = false;
          }
          if (e.key === "ArrowLeft") {
            inputState.left_down = false;
          }
          if (e.key === "ArrowRight") {
            inputState.right_down = false;
          }
        });

        const setup = wasm.instance.exports.setup;
        setup();

        const fps = new FPSCounter();

        const mainLoop = () => {
          fps.tick();

          const before = Date.now();
          // clear the screen
          ctx.clearRect(0, 0, canvas.width, canvas.height);

          // Let's figure out how long it takes to run loop.
          exports.loop(
            inputState.right_down,
            inputState.right_pressed,
            inputState.up_down,
            inputState.up_pressed,
            inputState.down_down,
            inputState.down_pressed,
            inputState.left_down,
            inputState.left_pressed,
            inputState.a_down,
            inputState.a_pressed,
            inputState.b_down,
            inputState.b_pressed
          );

          inputState.a_pressed = false;
          inputState.b_pressed = false;
          inputState.up_pressed = false;
          inputState.down_pressed = false;
          inputState.left_pressed = false;
          inputState.right_pressed = false;

          const after = Date.now();

          // Attempt to loop at 30fps.
          // TODO: Come up with a better scheme for this.
          const wait = Math.max(0, 33.0 - (after - before));
          setTimeout(mainLoop, wait);
        };

        mainLoop();
      })();
    </script>
  </body>
</html>