Undo System

Overview

The level editor (WM_PHASE_BUILD) supports a single-step undo: at most one world state snapshot exists at any time, and can be restored once.

Implementation: src/decor.cpp, CDecor::Undo*() methods.

API

void CDecor::UndoOpen();
// Begins recording changes — prepares the snapshot slot.
// Called immediately before a destructive operation (place/delete tile, build etc.)

void CDecor::UndoCopy();
// Copies the current m_decor[100][100] state into m_pUndoDecor.
// Allocates heap memory if not yet allocated.

void CDecor::UndoClose();
// Finalises the snapshot — marks it as valid.

void CDecor::UndoBack();
// Restores the world state from the snapshot:
//   memcpy(m_decor, m_pUndoDecor, sizeof(m_decor))
// Invalidates the snapshot (undo cannot be used again).

BOOL CDecor::IsUndo();
// Returns TRUE if a valid snapshot exists.
// Used to enable/disable the Undo button in the editor.

Implementation Details

• Snapshot stored in m_pUndoDecor — heap-allocated copy of m_decor[100][100]
• Only Cellule data is copied (floor + object tiles), not characters or animations
• Undo is only available in the editor (m_bBuild = TRUE), not during gameplay
• After UndoBack(), the snapshot is invalidated — no redo is possible
• Total snapshot size: 100 * 100 * sizeof(Cellule) bytes

Typical Call Sequence

// Before a destructive operation in the editor:
pDecor->UndoOpen();
pDecor->UndoCopy();
// ... perform change ...
pDecor->UndoClose();

// On Ctrl+Z / Undo button:
if (pDecor->IsUndo()) {
    pDecor->UndoBack();
}