Implement Native C++ gRPC Reader in Qt

[melaniereis]

1 - Short description

Modify the existing Qt Dashboard (myqtapp) to support dual data ingestion modes: direct CAN Bus (via SocketCAN) and KUKSA Databroker (via gRPC). The application must determine which mode to use at runtime via command-line arguments. This involves linking against native Google gRPC libraries and implementing a threaded KuksaReader class.

2 - Tasks

• Update CMakeLists.txt to find and link gRPC::grpc++, Protobuf::protobuf, and absl libraries.

• Configure CMake to auto-generate C++ source code from val.proto and types.proto using protoc.

• Create KuksaReader class (inheriting QObject) to handle gRPC communication.

• Implement the gRPC Subscribe loop in a worker thread to prevent blocking the Qt UI.

• Implement QCommandLineParser in main.cpp to handle the --kuksa / -k flag.

• Wire up VehicleData slots to either CANReader or KuksaReader signals based on the runtime flag.

• Linking: Application starts on the target without "Symbol Lookup Error" (verifying absl and grpc linking).

• Default Mode: Running the app without arguments (./myqtapp) starts in CAN Mode (opens vcan0 socket).

• KUKSA Mode: Running the app with ./myqtapp --kuksa starts in KUKSA Mode and attempts to connect to localhost:55555.

• Data Flow: In KUKSA mode, incoming gRPC speed updates successfully trigger the speedometer animation in QML.

4 - Implementation Notes

• Architecture: We are using native libgrpc++ to ensure Apache 2.0 compliance and better compatibility with AGL layers compared to QtGrpc.
• Threading: The gRPC Read() loop is blocking, so the KuksaReader must be moved to a QThread to keep the GUI responsive.
• Verification: Latency testing logs are included to verify performance differences between direct CAN and KUKSA paths.