ubo-lvgl-gui-client

Python launcher and gRPC bridge for the LVGL (C) GUI renderer. It connects to the ubo-core gRPC server, translates ViewData/StatusBarData into calls on the C renderer (libubo_lvgl) via CFFI, forwards keypad input, and answers screenshot requests.

Run (from the repo root):

uv run ubo-core   # serves 127.0.0.1:50051
uv run --directory ubo_app/lvgl_gui python -m ubo_lvgl_gui_client --backend sdl

Modules: bridge.py (CFFI ↔ C structs), client.py (gRPC subscribe/reconnect), view_translator.py (betterproto → bridge), keyboard.py, screenshot.py, __main__.py.

Transports

The client can reach ubo-core over two wire transports, selected at launch:

• grpc (default) — native gRPC over HTTP/2 (UboRPCClient, grpclib), connecting directly to the core's gRPC port (--host/--port).
• web-grpc — gRPC-Web over HTTP/1.1 through an Envoy proxy (the same /grpc endpoint the web-UI uses, default Envoy port 50052). Intended for resource-constrained targets where an HTTP/2 gRPC stack is impractical.

Select via flags or environment variables:

# native gRPC (default)
python -m ubo_lvgl_gui_client --transport grpc --host ubo-r.local --port 50051

# gRPC-Web via Envoy
UBO_LVGL_GUI_TRANSPORT=web-grpc \
UBO_LVGL_GUI_WEB_GRPC_URL=http://ubo-r.local:50052/grpc \
  python -m ubo_lvgl_gui_client

Only the wire layer differs — request/response bodies are the identical protobuf messages, so the betterproto bindings are reused for both. grpc_web_frame.py holds the dependency-free framing codec and is the portability boundary for the eventual ESP32 (C) port: that module maps 1:1 to a C buffer-and-drain loop (swap betterproto for nanopb and httpx for esp_http_client).

See ubo_lvgl/README.md at the repo root for the full architecture, build, and run guide (the C renderer is the main component).