DEMO 'STOCKFISH' +SOURCE

Demo: Stockfish.G32 — summary

What this demo does

• Loads Stockfish (external chess engine) from a user-specified path and asks it for the best move for a given FEN string.
• Demonstrates interop between GFA‑Basic 32 and a native DLL (StockfishBridge.dll) that launches Stockfish, speaks UCI, and returns the best move as a string.

Files and components

• Stockfish.G32 — the GFA demo program (code you posted).
• StockfishBridge.dll — native helper DLL (C++) that starts stockfish.exe, sends UCI commands, and returns bestmove.
• stockfish_path.txt — sidecar file placed next to the EXE that holds the full path to stockfish.exe (created by the demo if missing).
• stockfish.exe — the engine binary (user-supplied).

Key features

• Runtime path setter: calls SetStockfishPath in the DLL so the engine location is configurable at runtime.
• FEN-based query: the demo forms a FEN string and calls GetBestMove(fen$) to receive Stockfish’s suggested move.
• User-friendly setup: if stockfish_path.txt is missing or invalid the demo prompts the user to enter the path and persists it.
• Basic validation: ValidFile uses GetAttr to ensure the supplied path exists, is not a directory, and has a .exe extension.
• Debug aids: DebugFeedback flag, Trace and Debug lines to help diagnose problems.

How to run (quick)

1. Place StockfishBridge.dll next to your GFA app and ensure the DLL export names match the Declares (SetStockfishPath, GetBestMove).
2. Put stockfish.exe anywhere you like. If you already have stockfish_path.txt with the correct full path, the demo will read it automatically.
3. Run the demo. If stockfish_path.txt is missing or wrong you’ll be prompted to paste the full path to stockfish.exe. . The demo writes stockfish_path.txt for future runs.
4. The demo loads the starting-position FEN and prints Stockfish’s recommendation in the debug window (example: e2e4).

Troubleshooting checklist

• "Path invalid" message: ensure the string you enter points to the actual stockfish.exe file and includes the .exe extension.
• DLL not found / load errors: verify StockfishBridge.dll is in the same folder as the GFA EXE or on the PATH, and its exports match the Declare lines.
• No move / engine timeout: the bundled DLL times out if the engine doesn’t respond; check that the engine runs when launched manually and that your antivirus isn’t blocking execution.
• Permission or write errors saving stockfish_path.txt: run from a writable folder (not Program Files) or change where the config file is saved.

Possible improvements you might discuss on the forum

• Replace InputBox with a standard file-open dialog (OPENFILENAME) for better UX.
• Add more robust error reporting from the DLL (return engine stderr or diagnostics).
• Allow users to choose engine options (threads, hash) by exposing more UCI options.
• Make GetBestMove accept optional parameters (movetime, depth) from GFA.
• Add a persistent GUI setting page instead of a simple text file.

One-line demo purpose to post A minimal GFA‑Basic demo that shows how to configure the path to stockfish.exe, call a DLL wrapper for Stockfish using UCI, and get the engine’s best move from a FEN position — with simple path validation and persistence via stockfish_path.txt.