InputMapper tracks a mouse-down over a placed piece and promotes it to
drag mode once the cursor travels past an 8px threshold. Legal drop
cells (those where the piece's start→end vector still fits a legal
placement) are highlighted in green. Releasing on a legal cell emits a
RelocateRequested signal; Main feeds it to MovePieceCommand, which is
already undoable via the existing history stack.
Escape or releasing on an invalid cell cancels. The harness gains a
relocate() helper so UI tests can script drag-and-drop moves without
synthesizing motion events.
GameSim snapshots the state before each undoable command
(PlacePiece / RemovePiece / MovePiece) into a bounded LinkedList stack
(max 32). Undo() pops the last checkpoint and emits StateRestoredEvent,
reusing the presentation rebuild path already wired for QuickLoad.
Ctrl+Z in Main triggers the engine method; the harness exposes undo()
for tests. QuickLoad clears the stack (fresh timeline). Seven unit tests
cover empty stack, place/remove/move undo, reverse-order multiple undos,
rejected commands not checkpointing, and post-simulation rewind.
BoardState.CaptureSave/RestoreFromSave deep-copy every mutable field
(grid, pieces, demands, transformers, buffers, stock, campaign progress)
into a WorldSave slot. GameSim.QuickSave/QuickLoad expose slotted saves
and emit StateSavedEvent / StateRestoredEvent — the latter carries a
fresh BoardSnapshot so the presentation can rebuild board, pieces,
trajectories, objectives, stock, camera, and control bar in one pass.
F5/F9 trigger it in Main; harness gains quick_save/quick_load commands so
UI tests can checkpoint a scenario and resume without replaying from
scratch. Seven xUnit tests cover the roundtrip (including independence
from post-save mutations, campaign state, and multi-slot isolation).
Launching Godot with --automation=<dir> activates an AutomationHarness
node that polls <dir>/inbox/ for JSON command files, executes them via
a thin facade over existing public surfaces (GameSim, InputMapper,
EventAnimator, ControlBar, PieceStockPanel), and writes results plus
screenshots back to disk. The black-box simulation boundary is not
crossed — every command routes through the same signals/methods a real
player would trigger.
A stdlib-only Python helper (tools/automation/harness.py) wraps the
protocol for test scripts and interactive REPLs. Smoke test passes
end-to-end: load mission, place a piece, step 10 turns, capture 14
1280x720 PNGs, handle rejections, quit cleanly. Existing 102 engine
unit tests still green.
