silly billy cursor

package.json

@@ -14,6 +14,8 @@
   "type": "module",
   "dependencies": {
     "@zip.js/zip.js": "^2.7.52",
+    "ani-cursor": "^0.0.5",
+    "riff-file": "^1.0.3",
     "sssg": "git+https://git.sad.ovh/sophie/sssg#e68ad369e9399d33f58678d2a3271cd631c2fe6a"
   }
 }

website/index.html

@@ -7,6 +7,7 @@ __TEMPLATE_HEAD__
 <script type="module" src="scripts/lastfm.js"></script>
 <script type="module" src="scripts/binkies.js"></script>
 <script type="module" src="scripts/commit.js"></script>
+<script type="module" src="scripts/cursor.js"></script>
 
 <link rel="stylesheet" href="assets/style.css">
 </head>

website/scripts/ani_parser.ts

@@ -0,0 +1,225 @@
+// Code by
+// https://www.npmjs.com/package/ani-cursor
+
+// When importing the NPM package it just doesn't work.
+// The babel version is so old it doesn't work on my browser.
+
+import { RIFFFile } from "riff-file";
+import { unpackArray, unpackString } from "byte-data";
+
+type Chunk = {
+  format: string;
+  chunkId: string;
+  chunkData: {
+    start: number;
+    end: number;
+  };
+  subChunks: Chunk[];
+};
+
+// https://www.informit.com/articles/article.aspx?p=1189080&seqNum=3
+type AniMetadata = {
+  cbSize: number; // Data structure size (in bytes)
+  nFrames: number; // Number of images (also known as frames) stored in the file
+  nSteps: number; // Number of frames to be displayed before the animation repeats
+  iWidth: number; // Width of frame (in pixels)
+  iHeight: number; // Height of frame (in pixels)
+  iBitCount: number; // Number of bits per pixel
+  nPlanes: number; // Number of color planes
+  iDispRate: number; // Default frame display rate (measured in 1/60th-of-a-second units)
+  bfAttributes: number; // ANI attribute bit flags
+};
+
+type ParsedAni = {
+  rate: number[] | null;
+  seq: number[] | null;
+  images: Uint8Array[];
+  metadata: AniMetadata;
+  artist: string | null;
+  title: string | null;
+};
+
+const DWORD = { bits: 32, be: false, signed: false, fp: false };
+
+export function parseAni(arr: Uint8Array): ParsedAni {
+  const riff = new RIFFFile();
+
+  riff.setSignature(arr);
+
+  const signature = riff.signature as Chunk;
+  if (signature.format !== "ACON") {
+    throw new Error(
+      `Expected format. Expected "ACON", got "${signature.format}"`
+    );
+  }
+
+  // Helper function to get a chunk by chunkId and transform it if it's non-null.
+  function mapChunk<T>(chunkId: string, mapper: (chunk: Chunk) => T): T | null {
+    const chunk = riff.findChunk(chunkId) as Chunk | null;
+    return chunk == null ? null : mapper(chunk);
+  }
+
+  function readImages(chunk: Chunk, frameCount: number): Uint8Array[] {
+    return chunk.subChunks.slice(0, frameCount).map((c) => {
+      if (c.chunkId !== "icon") {
+        throw new Error(`Unexpected chunk type in fram: ${c.chunkId}`);
+      }
+      return arr.slice(c.chunkData.start, c.chunkData.end);
+    });
+  }
+
+  const metadata = mapChunk("anih", (c) => {
+    const words = unpackArray(arr, DWORD, c.chunkData.start, c.chunkData.end);
+    return {
+      cbSize: words[0],
+      nFrames: words[1],
+      nSteps: words[2],
+      iWidth: words[3],
+      iHeight: words[4],
+      iBitCount: words[5],
+      nPlanes: words[6],
+      iDispRate: words[7],
+      bfAttributes: words[8],
+    };
+  });
+
+  if (metadata == null) {
+    throw new Error("Did not find anih");
+  }
+
+  const rate = mapChunk("rate", (c) => {
+    return unpackArray(arr, DWORD, c.chunkData.start, c.chunkData.end);
+  });
+  // chunkIds are always four chars, hence the trailing space.
+  const seq = mapChunk("seq ", (c) => {
+    return unpackArray(arr, DWORD, c.chunkData.start, c.chunkData.end);
+  });
+
+  const lists = riff.findChunk("LIST", true) as Chunk[] | null;
+  const imageChunk = lists?.find((c) => c.format === "fram");
+  if (imageChunk == null) {
+    throw new Error("Did not find fram LIST");
+  }
+
+  let images = readImages(imageChunk, metadata.nFrames);
+
+  let title: string | null = null;
+  let artist: string | null = null;
+
+  const infoChunk = lists?.find((c) => c.format === "INFO");
+  if (infoChunk != null) {
+    infoChunk.subChunks.forEach((c) => {
+      switch (c.chunkId) {
+        case "INAM":
+          title = unpackString(arr, c.chunkData.start, c.chunkData.end);
+          break;
+        case "IART":
+          artist = unpackString(arr, c.chunkData.start, c.chunkData.end);
+          break;
+        case "LIST":
+          // Some cursors with an artist of "Created with Take ONE 3.5 (unregisterred version)" seem to have their frames here for some reason?
+          if (c.format === "fram") {
+            images = readImages(c, metadata.nFrames);
+          }
+          break;
+
+        default:
+        // Unexpected subchunk
+      }
+    });
+  }
+
+  return { images, rate, seq, metadata, artist, title };
+}
+
+type AniCursorImage = {
+  frames: {
+    url: string;
+    percents: number[];
+  }[];
+  duration: number;
+};
+
+const JIFFIES_PER_MS = 1000 / 60;
+
+// Generate CSS for an animated cursor.
+//
+// This function returns CSS containing a set of keyframes with embedded Data
+// URIs as well as a CSS rule to the given selector.
+export function convertAniBinaryToCSS(
+  selector: string,
+  aniBinary: Uint8Array
+): string {
+  const ani = readAni(aniBinary);
+
+  const animationName = `ani-cursor-${uniqueId()}`;
+
+  const keyframes = ani.frames.map(({ url, percents }) => {
+    const percent = percents.map((num) => `${num}%`).join(", ");
+    return `${percent} { cursor: url(${url}), auto; }`;
+  });
+
+  // CSS properties with a animation type of "discrete", like `cursor`, actually
+  // switch half-way _between_ each keyframe percentage. Luckily this half-way
+  // measurement is applied _after_ the easing function is applied. So, we can
+  // force the frames to appear at exactly the % that we specify by using
+  // `timing-function` of `step-end`.
+  //
+  // https://drafts.csswg.org/web-animations-1/#discrete
+  const timingFunction = "step-end";
+
+  // Winamp (re)starts the animation cycle when your mouse enters an element. By
+  // default this approach would cause the animation to run continuously, even
+  // when the cursor is not visible. To match Winamp's behavior we add a
+  // `:hover` pseudo selector so that the animation only runs when the cursor is
+  // visible.
+  const pseudoSelector = ":hover";
+
+  // prettier-ignore
+  return `
+    @keyframes ${animationName} {
+        ${keyframes.join("\n")}
+    }
+    ${selector}${pseudoSelector} {
+        animation: ${animationName} ${ani.duration}ms ${timingFunction} infinite;
+    }
+   `;
+}
+
+function readAni(contents: Uint8Array): AniCursorImage {
+  const ani = parseAni(contents);
+  const rate = ani.rate ?? ani.images.map(() => ani.metadata.iDispRate);
+  const duration = sum(rate);
+
+  const frames = ani.images.map((image) => ({
+    url: curUrlFromByteArray(image),
+    percents: [] as number[],
+  }));
+
+  let elapsed = 0;
+  rate.forEach((r, i) => {
+    const frameIdx = ani.seq ? ani.seq[i] : i;
+    frames[frameIdx].percents.push((elapsed / duration) * 100);
+    elapsed += r;
+  });
+
+  return { duration: duration * JIFFIES_PER_MS, frames };
+}
+
+/* Utility Functions */
+
+let i = 0;
+const uniqueId = () => i++;
+
+function base64FromDataArray(dataArray: Uint8Array): string {
+  return globalThis.window ? window.btoa(String.fromCharCode(...dataArray)) : Buffer.from(dataArray).toString("base64");
+}
+
+function curUrlFromByteArray(arr: Uint8Array) {
+  const base64 = base64FromDataArray(arr);
+  return `data:image/x-win-bitmap;base64,${base64}`;
+}
+
+function sum(values: number[]): number {
+  return values.reduce((total, value) => total + value, 0);
+}

website/scripts/cursor.ts

@@ -0,0 +1,8 @@
+import { convertAniBinaryToCSS } from "./ani_parser";
+(async () => {
+  const req = await fetch("/assets/cursor.ani");
+  const buf = new Uint8Array(await req.arrayBuffer());
+  const style = document.createElement("style");
+  style.innerHTML = convertAniBinaryToCSS("body", buf);
+  document.body.appendChild(style);
+})();