Adjust memory allocation to allocate based on max element wire size

As we add features to the wire format, this makes is simplier to adjust
the memory allocation of the wasm

For example, the PR can add 24 new bytes of memory to an element
operation that defines border properties

probably not a big deal, but its nice to keep it in mind

Author: rauhryan

term-native.ts

@@ -16,6 +16,15 @@ const BoundingBoxStruct = struct<BoundingBox>({
 
 const BOUNDING_BOX = offsets(BoundingBoxStruct);
 
+const WASM_PAGE_BYTES = 65536;
+const TEXT_TRANSFER_BUFFER_BYTES = 1024 * 1024;
+const CLAY_DEFAULT_MAX_ELEMENT_COUNT = 8192;
+
+// Conservative fixed wire-format budget per element. This covers the largest
+// non-text open/close element encoding we currently support; text, element id,
+// and snapshot payload bytes live in TEXT_TRANSFER_BUFFER_BYTES.
+const MAX_FIXED_ELEMENT_WIRE_BYTES = 116;
+
 export interface Native {
   memory: WebAssembly.Memory;
   statePtr: number;
@@ -92,10 +101,15 @@ export async function createTermNative(
   let heap = ct.__heap_base.value as number;
   let size = ct.clayterm_size(w, h);
 
-  // grow memory to fit heap + state + ops buffer (1MB headroom for ops)
-  let needed = heap + size + 1024 * 1024;
-  let pages = Math.ceil(needed / 65536);
-  let current = memory.buffer.byteLength / 65536;
+  // Grow memory once to fit heap + renderer state + fixed transfer buffer.
+  // The transfer budget is intentionally fixed: text/id/snapshot payload bytes
+  // get 1MB, and fixed op overhead gets one max-sized element per Clay element.
+  // Do not grow this dynamically per render; improve the wire format instead.
+  let transferBytes = TEXT_TRANSFER_BUFFER_BYTES +
+    CLAY_DEFAULT_MAX_ELEMENT_COUNT * MAX_FIXED_ELEMENT_WIRE_BYTES;
+  let needed = heap + size + transferBytes;
+  let pages = Math.ceil(needed / WASM_PAGE_BYTES);
+  let current = memory.buffer.byteLength / WASM_PAGE_BYTES;
   if (pages > current) {
     memory.grow(pages - current);
   }