Download Progress

Set Options.on_progress to a Callable to track a download as it arrives. The callback fires once per chunk — on_progress.call(bytes_received, total_bytes) — where bytes_received is the cumulative count so far and total_bytes is the Content-Length, or -1 when the server doesn't send one (e.g. a chunked response). Compute a percentage only when total_bytes is positive.

var opts := C3Http.Options.new()
opts.on_progress = func(bytes_received: int, total_bytes: int) -> void:
    if total_bytes > 0:
        print("%d%%" % (bytes_received * 100 / total_bytes))
    else:
        print("%d bytes" % bytes_received)  # length unknown

var res := await C3Http.request("https://example.com/large.bin", PackedStringArray(), HTTPClient.METHOD_GET, "", opts)

Works for both in-memory and download_file downloads. bytes_received counts raw bytes off the wire, so it may differ from the final res.body.size() when a gzip body is decompressed after the transfer completes. It has no effect in SSE mode (on_sse_event), where the events themselves are the incremental signal.