main: add polyfill for old Supernote Webview

`.at` is missing from the Supernote webview. Polyfill it.

This took me awhile to figure out because the types that need the
polyfill aren't just the Array object. I am not a JS expert.

Fixes #43

Author: philips

README.md

@@ -90,3 +90,11 @@ npm link supernote-typescript/
 
 - `npm i` or `yarn` to install dependencies.
 - `npm run dev` to start compilation in watch mode.
+
+**Android Debugging**
+
+- Ensure `npm run dev` is running above
+- Create a vault called "SupernoteTest"
+- Install the supernote plugin from the community store
+- Run `npm run push-android` to push main.js to the device
+- Run "Reload App without Saving" on Obsidian command palette 

package-lock.json

@@ -6,15 +6,16 @@
 	"scripts": {
 		"dev": "node esbuild.config.mjs",
 		"build": "tsc -noEmit -skipLibCheck && node esbuild.config.mjs production",
-		"version": "node version-bump.mjs && git add manifest.json versions.json"
+		"version": "node version-bump.mjs && git add manifest.json versions.json",
+		"push-android": "adb push main.js /sdcard/Documents/SupernoteTest/.obsidian/plugins/supernote"
 	},
 	"keywords": [],
 	"author": "",
 	"license": "MIT",
 	"devDependencies": {
 		"@types/color": "^3.0.6",
 		"@types/jest": "^29.5.12",
-		"@types/node": "^16.11.6",
+		"@types/node": "^20.0.0",
 		"@typescript-eslint/eslint-plugin": "5.29.0",
 		"@typescript-eslint/parser": "5.29.0",
 		"builtin-modules": "3.3.0",

package.json

@@ -1,3 +1,4 @@
+import { installAtPolyfill } from './polyfills';
 import { App, Modal, TFile, Plugin, Editor, MarkdownView, WorkspaceLeaf, FileView } from 'obsidian';
 import { SupernotePluginSettings, SupernoteSettingTab, DEFAULT_SETTINGS } from './settings';
 import { SupernoteX, fetchMirrorFrame } from 'supernote-typescript';
@@ -386,6 +387,9 @@ export default class SupernotePlugin extends Plugin {
 	settings: SupernotePluginSettings;
 
 	async onload() {
+        // Install polyfills before any other code runs
+        installAtPolyfill();
+
 		await this.loadSettings();
 		vw = new VaultWriter(this.app, this.settings);
 
@@ -607,4 +611,4 @@ class ErrorModal extends Modal {
 		const { contentEl } = this;
 		contentEl.empty();
 	}
-}
+}

src/main.ts

@@ -1,7 +1,9 @@
+import { installAtPolyfill } from 'polyfills';
+installAtPolyfill();
+
 import { SupernoteX, toImage } from 'supernote-typescript';
-import { Image } from 'image-js'
 
-export {};
+export { };
 
 export type SupernoteWorkerMessage = {
     type: 'convert';
@@ -42,4 +44,4 @@ self.onmessage = async (e: MessageEvent<SupernoteWorkerMessage>) => {
             error: error instanceof Error ? error.message : 'Unknown error occurred'
         });
     }
-};
+};

src/myworker.worker.ts

@@ -0,0 +1,32 @@
+// Polyfill for Array.prototype.at and TypedArray.prototype.at.
+// This is necessary for SuperNote devices with old WebView versions.
+export function installAtPolyfill() {
+    if (!Array.prototype.at) {
+        const at = function(n: number) {
+            // ToInteger() abstract op
+            n = Math.trunc(n) || 0;
+            // Allow negative indexing from the end
+            if (n < 0) n += this.length;
+            // OOB access is guaranteed to return undefined
+            if (n < 0 || n >= this.length) return undefined;
+            // Otherwise, this is just normal property access
+            return this[n];
+        };
+
+        // Apply to Array and all TypedArray prototypes
+        const typedArrays = [
+            Int8Array, Uint8Array, Uint8ClampedArray,
+            Int16Array, Uint16Array,
+            Int32Array, Uint32Array,
+            Float32Array, Float64Array,
+            BigInt64Array, BigUint64Array
+        ];
+
+        Array.prototype.at = at;
+        typedArrays.forEach(TypedArray => {
+            if (TypedArray) {
+                TypedArray.prototype.at = at;
+            }
+        });
+    }
+}