Function requestFrame

packages/node/src/backend/nodeBackend.ts:745–839

(drawlist: Uint8Array)

    },

    requestFrame(drawlist: Uint8Array): Promise<void> {
      if (disposed) return Promise.reject(new Error("NodeBackend: disposed"));
      if (fatal !== null) return Promise.reject(fatal);
      if (stopRequested) return Promise.reject(new Error("NodeBackend: stopped"));
      if (!started) {
        return backend.start().then(() => backend.requestFrame(drawlist));
      }
      if (worker === null) return Promise.reject(new Error("NodeBackend: worker not available"));

      const frameSeq = nextFrameSeq++;
      const framePromise = reserveFramePromise(frameTracking, frameSeq);

      if (sabFrameTransport !== null && drawlist.byteLength <= sabFrameTransport.slotBytes) {
        const slotIndex = acquireSabSlot(sabFrameTransport);
        if (slotIndex >= 0) {
          const slotToken = frameSeqToSlotToken(frameSeq);
          registerFrameAudit(
            frameTracking,
            frameAudit,
            frameSeq,
            "requestFrame",
            FRAME_TRANSPORT_SAB_V1,
            drawlist,
            slotIndex,
            slotToken,
          );
          const slotOffset = slotIndex * sabFrameTransport.slotBytes;
          sabFrameTransport.dataBytes.set(drawlist, slotOffset);
          Atomics.store(sabFrameTransport.tokens, slotIndex, slotToken);
          Atomics.store(sabFrameTransport.states, slotIndex, FRAME_SAB_SLOT_STATE_READY);
          publishSabFrame(sabFrameTransport, frameSeq, slotIndex, slotToken, drawlist.byteLength);
          if (frameAudit.enabled) {
            frameAudit.emit("frame.sab.publish", {
              frameSeq,
              slotIndex,
              slotToken,
              byteLen: drawlist.byteLength,
            });
          }
          // SAB consumers wake on futex notify instead of per-frame
          // MessagePort frameKick round-trips.
          Atomics.notify(sabFrameTransport.controlHeader, FRAME_SAB_CONTROL_PUBLISHED_SEQ_WORD, 1);
          return framePromise;
        }
        if (frameAudit.enabled) {
          frameAudit.emit("frame.sab.fallback_transfer", {
            frameSeq,
            byteLen: drawlist.byteLength,
            reason: "no-slot-available",
          });
        }
      }

      // Transfer fallback participates in the same ACK model:
      // - accepted ACK (hidden marker) can unblock app scheduling early
      // - completion promise settles on worker completion/coalescing status
      const buf = new ArrayBuffer(drawlist.byteLength);
      copyInto(buf, drawlist);