1 files changed, 57 insertions, 0 deletions
diff --git a/packages/excalidraw/subset/harfbuzz/harfbuzz-loader.ts b/packages/excalidraw/subset/harfbuzz/harfbuzz-loader.ts
new file mode 100644
index 0000000..9a48d19
--- /dev/null
+++ b/packages/excalidraw/subset/harfbuzz/harfbuzz-loader.ts
@@ -0,0 +1,57 @@
+/**
+ * DON'T depend on anything from the outside like `promiseTry`, as this module is part of a separate lazy-loaded chunk.
+ *
+ * Including anything from the main chunk would include the whole chunk by default.
+ * Even it it would be tree-shaken during build, it won't be tree-shaken in dev.
+ *
+ * In the future consider separating common utils into a separate shared chunk.
+ */
+
+import binary from "./harfbuzz-wasm";
+import bindings from "./harfbuzz-bindings";
+
+/**
+ * Lazy loads wasm and respective bindings for font subsetting based on the harfbuzzjs.
+ */
+let loadedWasm: ReturnType<typeof load> | null = null;
+
+// TODO: consider adding support for fetching the wasm from an URL (external CDN, data URL, etc.)
+const load = (): Promise<{
+  subset: (
+    fontBuffer: ArrayBuffer,
+    codePoints: ReadonlySet<number>,
+  ) => Uint8Array;
+}> => {
+  return new Promise(async (resolve, reject) => {
+    try {
+      const module = await WebAssembly.instantiate(binary);
+      const harfbuzzJsWasm = module.instance.exports;
+      // @ts-expect-error since `.buffer` is custom prop
+      const heapu8 = new Uint8Array(harfbuzzJsWasm.memory.buffer);
+
+      const hbSubset = {
+        subset: (fontBuffer: ArrayBuffer, codePoints: ReadonlySet<number>) => {
+          return bindings.subset(
+            harfbuzzJsWasm,
+            heapu8,
+            fontBuffer,
+            codePoints,
+          );
+        },
+      };
+
+      resolve(hbSubset);
+    } catch (e) {
+      reject(e);
+    }
+  });
+};
+
+// lazy load the default export
+export default (): ReturnType<typeof load> => {
+  if (!loadedWasm) {
+    loadedWasm = load();
+  }
+
+  return loadedWasm;
+};