gtkradiant/radiant/undo.cpp

/*
   Copyright (C) 1999-2007 id Software, Inc. and contributors.
   For a list of contributors, see the accompanying CONTRIBUTORS file.

   This file is part of GtkRadiant.

   GtkRadiant is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; either version 2 of the License, or
   (at your option) any later version.

   GtkRadiant is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with GtkRadiant; if not, write to the Free Software
   Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 */


/*

   QERadiant Undo/Redo


   basic setup:

   <-g_undolist---------g_lastundo> <---map data---> <-g_lastredo---------g_redolist->


   undo/redo on the world_entity is special, only the epair changes are remembered
   and the world entity never gets deleted.

   FIXME: maybe reset the Undo system at map load
         maybe also reset the entityId at map load
 */

#include "stdafx.h"

typedef struct undo_s
{
	double time;                //time operation was performed
	int id;                     //every undo has an unique id
	int done;                   //true when undo is build
	const char *operation;          //name of the operation
	brush_t brushlist;          //deleted brushes
	entity_t entitylist;        //deleted entities
	struct undo_s *prev, *next; //next and prev undo in list
} undo_t;

undo_t *g_undolist;                     //first undo in the list
undo_t *g_lastundo;                     //last undo in the list
undo_t *g_redolist;                     //first redo in the list
undo_t *g_lastredo;                     //last undo in list
int g_undoMaxSize = 64;                 //maximum number of undos
int g_undoSize = 0;                     //number of undos in the list
int g_undoMaxMemorySize = 2 * 1024 * 1024;  //maximum undo memory (default 2 MB)
int g_undoMemorySize = 0;               //memory size of undo buffer
int g_undoId = 1;                       //current undo ID (zero is invalid id)
int g_redoId = 1;                       //current redo ID (zero is invalid id)

/*
   =============
   Undo_MemorySize
   =============
 */
int Undo_MemorySize( void ){
	return g_undoMemorySize;
}

/*
   =============
   Undo_ClearRedo
   =============
 */
void Undo_ClearRedo( void ){
	undo_t *redo, *nextredo;
	brush_t *pBrush, *pNextBrush;
	entity_t *pEntity, *pNextEntity;

	for ( redo = g_redolist; redo; redo = nextredo )
	{
		nextredo = redo->next;
		for ( pBrush = redo->brushlist.next ; pBrush != NULL && pBrush != &redo->brushlist ; pBrush = pNextBrush )
		{
			pNextBrush = pBrush->next;
			Brush_Free( pBrush );
		}
		for ( pEntity = redo->entitylist.next; pEntity != NULL && pEntity != &redo->entitylist; pEntity = pNextEntity )
		{
			pNextEntity = pEntity->next;
			Entity_Free( pEntity );
		}
		free( redo );
	}
	g_redolist = NULL;
	g_lastredo = NULL;
	g_redoId = 1;
}

/*
   =============
   Undo_Clear

   Clears the undo buffer.
   =============
 */
void Undo_Clear( void ){
	undo_t *undo, *nextundo;
	brush_t *pBrush, *pNextBrush;
	entity_t *pEntity, *pNextEntity;

	Undo_ClearRedo();
	for ( undo = g_undolist; undo; undo = nextundo )
	{
		nextundo = undo->next;
		for ( pBrush = undo->brushlist.next ; pBrush != NULL && pBrush != &undo->brushlist ; pBrush = pNextBrush )
		{
			pNextBrush = pBrush->next;
			g_undoMemorySize -= Brush_MemorySize( pBrush );
			Brush_Free( pBrush );
		}
		for ( pEntity = undo->entitylist.next; pEntity != NULL && pEntity != &undo->entitylist; pEntity = pNextEntity )
		{
			pNextEntity = pEntity->next;
			g_undoMemorySize -= Entity_MemorySize( pEntity );
			Entity_Free( pEntity );
		}
		g_undoMemorySize -= sizeof( undo_t );
		free( undo );
	}
	g_undolist = NULL;
	g_lastundo = NULL;
	g_undoSize = 0;
	g_undoMemorySize = 0;
	g_undoId = 1;
}

/*
   =============
   Undo_SetMaxSize
   =============
 */
void Undo_SetMaxSize( int size ){
	Undo_Clear();
	if ( size < 1 ) {
		g_undoMaxSize = 1;
	}
	else{g_undoMaxSize = size; }
}

/*
   =============
   Undo_GetMaxSize
   =============
 */
int Undo_GetMaxSize( void ){
	return g_undoMaxSize;
}

/*
   =============
   Undo_SetMaxMemorySize
   =============
 */
void Undo_SetMaxMemorySize( int size ){
	Undo_Clear();
	if ( size < 1024 ) {
		g_undoMaxMemorySize = 1024;
	}
	else{g_undoMaxMemorySize = size; }
}

/*
   =============
   Undo_GetMaxMemorySize
   =============
 */
int Undo_GetMaxMemorySize( void ){
	return g_undoMaxMemorySize;
}

/*
   =============
   Undo_FreeFirstUndo
   =============
 */
void Undo_FreeFirstUndo( void ){
	undo_t *undo;
	brush_t *pBrush, *pNextBrush;
	entity_t *pEntity, *pNextEntity;

	//remove the oldest undo from the undo buffer
	undo = g_undolist;
	g_undolist = g_undolist->next;
	g_undolist->prev = NULL;
	//
	for ( pBrush = undo->brushlist.next ; pBrush != NULL && pBrush != &undo->brushlist ; pBrush = pNextBrush )
	{
		pNextBrush = pBrush->next;
		g_undoMemorySize -= Brush_MemorySize( pBrush );
		Brush_Free( pBrush );
	}
	for ( pEntity = undo->entitylist.next; pEntity != NULL && pEntity != &undo->entitylist; pEntity = pNextEntity )
	{
		pNextEntity = pEntity->next;
		g_undoMemorySize -= Entity_MemorySize( pEntity );
		Entity_Free( pEntity );
	}
	g_undoMemorySize -= sizeof( undo_t );
	free( undo );
	g_undoSize--;
}

/*
   =============
   Undo_GeneralStart
   =============
 */
void Undo_GeneralStart( const char *operation ){
	undo_t *undo;
	brush_t *pBrush;
	entity_t *pEntity;


	if ( g_lastundo ) {
		if ( !g_lastundo->done ) {
			Sys_FPrintf( SYS_WRN, "WARNING last undo not finished.\n" );
		}
	}

	undo = (undo_t *) malloc( sizeof( undo_t ) );
	if ( !undo ) {
		return;
	}
	memset( undo, 0, sizeof( undo_t ) );
	undo->brushlist.next = &undo->brushlist;
	undo->brushlist.prev = &undo->brushlist;
	undo->entitylist.next = &undo->entitylist;
	undo->entitylist.prev = &undo->entitylist;
	if ( g_lastundo ) {
		g_lastundo->next = undo;
	}
	else{
		g_undolist = undo;
	}
	undo->prev = g_lastundo;
	undo->next = NULL;
	g_lastundo = undo;

	undo->time = Sys_DoubleTime();
	//
	if ( g_undoId > g_undoMaxSize * 2 ) {
		g_undoId = 1;
	}
	if ( g_undoId <= 0 ) {
		g_undoId = 1;
	}
	undo->id = g_undoId++;
	undo->done = false;
	undo->operation = operation;
	//reset the undo IDs of all brushes using the new ID
	for ( pBrush = active_brushes.next; pBrush != NULL && pBrush != &active_brushes; pBrush = pBrush->next )
	{
		if ( pBrush->undoId == undo->id ) {
			pBrush->undoId = 0;
		}
	}
	for ( pBrush = selected_brushes.next; pBrush != NULL && pBrush != &selected_brushes; pBrush = pBrush->next )
	{
		if ( pBrush->undoId == undo->id ) {
			pBrush->undoId = 0;
		}
	}
	//reset the undo IDs of all entities using thew new ID
	for ( pEntity = entities.next; pEntity != NULL && pEntity != &entities; pEntity = pEntity->next )
	{
		if ( pEntity->undoId == undo->id ) {
			pEntity->undoId = 0;
		}
	}
	g_undoMemorySize += sizeof( undo_t );
	g_undoSize++;
	//undo buffer is bound to a max
	if ( g_undoSize > g_undoMaxSize ) {
		Undo_FreeFirstUndo();
	}
}

/*
   =============
   Undo_BrushInUndo
   =============
 */
int Undo_BrushInUndo( undo_t *undo, brush_t *brush ){
/*	brush_t *b;

    for (b = undo->brushlist.next; b != &undo->brushlist; b = b->next)
    {
    // Arnout: NOTE - can't do a pointer compare as the brushes get cloned into the undo brushlist, and not just referenced from it
    // For entities we have a unique ID, for brushes we have numberID - but brush full clone increases that anyway so it's useless right now.
        if (b == brush) return true;
    }*/
	// Arnout: function is pointless right now, see above explanation
	return false;
}

/*
   =============
   Undo_EntityInUndo
   =============
 */
int Undo_EntityInUndo( undo_t *undo, entity_t *ent ){
	entity_t *e;

	for ( e = undo->entitylist.next; e != &undo->entitylist; e = e->next )
	{
		// Arnout: NOTE - can't do a pointer compare as the entities get cloned into the undo entitylist, and not just referenced from it
		//if (e == ent) return true;
		if ( e->entityId == ent->entityId ) {
			return true;
		}
	}
	return false;
}

/*
   =============
   Undo_Start
   =============
 */
void Undo_Start( const char *operation ){
	// spog - disable undo if undo levels = 0
	if ( g_PrefsDlg.m_nUndoLevels == 0 ) {
#ifdef DBG_UNDO
		Sys_Printf( "Undo_Start: undo is disabled.\n" );
#endif
		return;
	}

	Undo_ClearRedo();
	Undo_GeneralStart( operation );
}

/*
   =============
   Undo_AddBrush
   =============
 */
void Undo_AddBrush( brush_t *pBrush ){
	// spog - disable undo if undo levels = 0
	if ( g_PrefsDlg.m_nUndoLevels == 0 ) {
#ifdef DBG_UNDO
		Sys_Printf( "Undo_AddBrush: undo is disabled.\n" );
#endif
		return;
	}

	if ( !g_lastundo ) {
		Sys_Printf( "Undo_AddBrushList: no last undo.\n" );
		return;
	}
	if ( g_lastundo->entitylist.next != &g_lastundo->entitylist ) {
		Sys_FPrintf( SYS_WRN, "WARNING adding brushes after entity.\n" );
	}
	//if the brush is already in the undo
	if ( Undo_BrushInUndo( g_lastundo, pBrush ) ) {
		return;
	}
	//clone the brush
	brush_t* pClone = Brush_FullClone( pBrush );
	//save the ID of the owner entity
	pClone->ownerId = pBrush->owner->entityId;
	//save the old undo ID for previous undos
	pClone->undoId = pBrush->undoId;
	Brush_AddToList( pClone, &g_lastundo->brushlist );
	//
	g_undoMemorySize += Brush_MemorySize( pClone );
}

/*
   =============
   Undo_AddBrushList
   TTimo: some brushes are just there for UI, and the information is somewhere else
   for patches it's in the patchMesh_t structure, so when we clone the brush we get that information (brush_t::pPatch)
   but: models are stored in pBrush->owner->md3Class, and owner epairs and origin parameters are important
   so, we detect models and push the entity in the undo session (as well as it's BBox brush)
    same for other items like weapons and ammo etc.
   =============
 */
void Undo_AddBrushList( brush_t *brushlist ){
	// spog - disable undo if undo levels = 0
	if ( g_PrefsDlg.m_nUndoLevels == 0 ) {
#ifdef DBG_UNDO
		Sys_Printf( "Undo_AddBrushList: undo is disabled.\n" );
#endif
		return;
	}

	brush_t *pBrush;

	if ( !g_lastundo ) {
		Sys_Printf( "Undo_AddBrushList: no last undo.\n" );
		return;
	}
	if ( g_lastundo->entitylist.next != &g_lastundo->entitylist ) {
		Sys_FPrintf( SYS_WRN, "WARNING adding brushes after entity.\n" );
	}
	//copy the brushes to the undo
	for ( pBrush = brushlist->next ; pBrush != NULL && pBrush != brushlist; pBrush = pBrush->next )
	{
		//if the brush is already in the undo
		//++timo FIXME: when does this happen?
		if ( Undo_BrushInUndo( g_lastundo, pBrush ) ) {
			continue;
		}
		// do we need to store this brush's entity in the undo?
		// if it's a fixed size entity, the brush that reprents it is not really relevant, it's used for selecting and moving around
		// what we want to store for undo is the owner entity, epairs and origin/angle stuff
		//++timo FIXME: if the entity is not fixed size I don't know, so I don't do it yet
		if ( pBrush->owner->eclass->fixedsize == 1 ) {
			Undo_AddEntity( pBrush->owner );
		}
		// clone the brush
		brush_t* pClone = Brush_FullClone( pBrush );
		// save the ID of the owner entity
		pClone->ownerId = pBrush->owner->entityId;
		// save the old undo ID from previous undos
		pClone->undoId = pBrush->undoId;
		Brush_AddToList( pClone, &g_lastundo->brushlist );
		// track memory size used by undo
		g_undoMemorySize += Brush_MemorySize( pClone );
	}
}

/*
   =============
   Undo_EndBrush
   =============
 */
void Undo_EndBrush( brush_t *pBrush ){
	// spog - disable undo if undo levels = 0
	if ( g_PrefsDlg.m_nUndoLevels == 0 ) {
#ifdef DBG_UNDO
		Sys_Printf( "Undo_EndBrush: undo is disabled.\n" );
#endif
		return;
	}


	if ( !g_lastundo ) {
		//Sys_Printf("Undo_End: no last undo.\n");
		return;
	}
	if ( g_lastundo->done ) {
		//Sys_Printf("Undo_End: last undo already finished.\n");
		return;
	}
	pBrush->undoId = g_lastundo->id;
}

/*
   =============
   Undo_EndBrushList
   =============
 */
void Undo_EndBrushList( brush_t *brushlist ){
	// spog - disable undo if undo levels = 0
	if ( g_PrefsDlg.m_nUndoLevels == 0 ) {
#ifdef DBG_UNDO
		Sys_Printf( "Undo_EndBrushList: undo is disabled.\n" );
#endif
		return;
	}


	if ( !g_lastundo ) {
		//Sys_Printf("Undo_End: no last undo.\n");
		return;
	}
	if ( g_lastundo->done ) {
		//Sys_Printf("Undo_End: last undo already finished.\n");
		return;
	}
	for ( brush_t* pBrush = brushlist->next; pBrush != NULL && pBrush != brushlist; pBrush = pBrush->next )
	{
		pBrush->undoId = g_lastundo->id;
		// http://github.com/mfn/GtkRadiant/commit/ee1ef98536470d5680bd9bfecc5b5c9a62ffe9ab
		if ( pBrush->owner->eclass->fixedsize == 1 ) {
			pBrush->owner->undoId = pBrush->undoId;
		}
	}
}

/*
   =============
   Undo_AddEntity
   =============
 */
void Undo_AddEntity( entity_t *entity ){
	// spog - disable undo if undo levels = 0
	if ( g_PrefsDlg.m_nUndoLevels == 0 ) {
#ifdef DBG_UNDO
		Sys_Printf( "Undo_AddEntity: undo is disabled.\n" );
#endif
		return;
	}


	entity_t* pClone;

	if ( !g_lastundo ) {
		Sys_Printf( "Undo_AddEntity: no last undo.\n" );
		return;
	}
	//if the entity is already in the undo
	if ( Undo_EntityInUndo( g_lastundo, entity ) ) {
		return;
	}
	//clone the entity
	pClone = Entity_Clone( entity );
	//save the old undo ID for previous undos
	pClone->undoId = entity->undoId;
	//save the entity ID (we need a full clone)
	pClone->entityId = entity->entityId;
	//
	Entity_AddToList( pClone, &g_lastundo->entitylist );
	//
	g_undoMemorySize += Entity_MemorySize( pClone );
}

/*
   =============
   Undo_EndEntity
   =============
 */
void Undo_EndEntity( entity_t *entity ){
	// spog - disable undo if undo levels = 0
	if ( g_PrefsDlg.m_nUndoLevels == 0 ) {
#ifdef DBG_UNDO
		Sys_Printf( "Undo_EndEntity: undo is disabled.\n" );
#endif
		return;
	}


	if ( !g_lastundo ) {
#ifdef _DEBUG
		Sys_Printf( "Undo_End: no last undo.\n" );
#endif
		return;
	}
	if ( g_lastundo->done ) {
#ifdef _DEBUG
		Sys_Printf( "Undo_End: last undo already finished.\n" );
#endif
		return;
	}
	if ( entity == world_entity ) {
		//Sys_Printf("Undo_AddEntity: undo on world entity.\n");
		//NOTE: we never delete the world entity when undoing an operation
		//		we only transfer the epairs
		return;
	}
	entity->undoId = g_lastundo->id;
}

/*
   =============
   Undo_End
   =============
 */
void Undo_End( void ){
	// spog - disable undo if undo levels = 0
	if ( g_PrefsDlg.m_nUndoLevels == 0 ) {
#ifdef DBG_UNDO
		Sys_Printf( "Undo_End: undo is disabled.\n" );
#endif
		return;
	}


	if ( !g_lastundo ) {
		//Sys_Printf("Undo_End: no last undo.\n");
		return;
	}
	if ( g_lastundo->done ) {
		//Sys_Printf("Undo_End: last undo already finished.\n");
		return;
	}
	g_lastundo->done = true;

	//undo memory size is bound to a max
	while ( g_undoMemorySize > g_undoMaxMemorySize )
	{
		//always keep one undo
		if ( g_undolist == g_lastundo ) {
			break;
		}
		Undo_FreeFirstUndo();
	}
	//
	//Sys_Printf("undo size = %d, undo memory = %d\n", g_undoSize, g_undoMemorySize);
}

/*
   =============
   Undo_Undo
   =============
 */
void Undo_Undo( qboolean bSilent ){
	// spog - disable undo if undo levels = 0
	if ( g_PrefsDlg.m_nUndoLevels == 0 ) {
		Sys_Printf( "Undo_Undo: undo is disabled.\n" );
		return;
	}

	undo_t *undo, *redo;
	brush_t *pBrush, *pNextBrush;
	entity_t *pEntity, *pNextEntity, *pUndoEntity;

	if ( !g_lastundo ) {
		Sys_Printf( "Nothing left to undo.\n" );
		return;
	}
	if ( !g_lastundo->done ) {
		Sys_FPrintf( SYS_WRN, "WARNING: last undo not yet finished!\n" );
	}
	// get the last undo
	undo = g_lastundo;
	if ( g_lastundo->prev ) {
		g_lastundo->prev->next = NULL;
	}
	else{g_undolist = NULL; }
	g_lastundo = g_lastundo->prev;

	//allocate a new redo
	redo = (undo_t *) malloc( sizeof( undo_t ) );
	if ( !redo ) {
		return;
	}
	memset( redo, 0, sizeof( undo_t ) );
	redo->brushlist.next = &redo->brushlist;
	redo->brushlist.prev = &redo->brushlist;
	redo->entitylist.next = &redo->entitylist;
	redo->entitylist.prev = &redo->entitylist;
	if ( g_lastredo ) {
		g_lastredo->next = redo;
	}
	else{g_redolist = redo; }
	redo->prev = g_lastredo;
	redo->next = NULL;
	g_lastredo = redo;
	redo->time = Sys_DoubleTime();
	redo->id = g_redoId++;
	redo->done = true;
	redo->operation = undo->operation;

	//reset the redo IDs of all brushes using the new ID
	for ( pBrush = active_brushes.next; pBrush != NULL && pBrush != &active_brushes; pBrush = pBrush->next )
	{
		if ( pBrush->redoId == redo->id ) {
			pBrush->redoId = 0;
		}
	}
	for ( pBrush = selected_brushes.next; pBrush != NULL && pBrush != &selected_brushes; pBrush = pBrush->next )
	{
		if ( pBrush->redoId == redo->id ) {
			pBrush->redoId = 0;
		}
	}
	//reset the redo IDs of all entities using thew new ID
	for ( pEntity = entities.next; pEntity != NULL && pEntity != &entities; pEntity = pEntity->next )
	{
		if ( pEntity->redoId == redo->id ) {
			pEntity->redoId = 0;
		}
	}

	// deselect current sutff
	Select_Deselect();
	// move "created" brushes to the redo
	for ( pBrush = active_brushes.next; pBrush != NULL && pBrush != &active_brushes; pBrush = pNextBrush )
	{
		pNextBrush = pBrush->next;
		if ( pBrush->undoId == undo->id ) {
			//Brush_Free(pBrush);
			//move the brush to the redo
			Brush_RemoveFromList( pBrush );
			Brush_AddToList( pBrush, &redo->brushlist );
			//make sure the ID of the owner is stored
			pBrush->ownerId = pBrush->owner->entityId;
			//unlink the brush from the owner entity
			Entity_UnlinkBrush( pBrush );
		}
	}
	// move "created" entities to the redo
	for ( pEntity = entities.next; pEntity != NULL && pEntity != &entities; pEntity = pNextEntity )
	{
		pNextEntity = pEntity->next;
		if ( pEntity->undoId == undo->id ) {
			// check if this entity is in the undo
			for ( pUndoEntity = undo->entitylist.next; pUndoEntity != NULL && pUndoEntity != &undo->entitylist; pUndoEntity = pUndoEntity->next )
			{
				// move brushes to the undo entity
				if ( pUndoEntity->entityId == pEntity->entityId ) {
					pUndoEntity->brushes.next = pEntity->brushes.next;
					pUndoEntity->brushes.prev = pEntity->brushes.prev;
					pEntity->brushes.next = &pEntity->brushes;
					pEntity->brushes.prev = &pEntity->brushes;
				}
			}
			//
			//Entity_Free(pEntity);
			//move the entity to the redo
			Entity_RemoveFromList( pEntity );
			Entity_AddToList( pEntity, &redo->entitylist );
		}
	}
	// add the undo entities back into the entity list
	for ( pEntity = undo->entitylist.next; pEntity != NULL && pEntity != &undo->entitylist; pEntity = undo->entitylist.next )
	{
		g_undoMemorySize -= Entity_MemorySize( pEntity );
		//if this is the world entity
		if ( pEntity->entityId == world_entity->entityId ) {
			epair_t* tmp = world_entity->epairs;
			world_entity->epairs = pEntity->epairs;
			pEntity->epairs = tmp;
			Entity_Free( pEntity );
		}
		else
		{
			Entity_RemoveFromList( pEntity );
			Entity_AddToList( pEntity, &entities );
			pEntity->redoId = redo->id;
		}
	}
	// add the undo brushes back into the selected brushes
	for ( pBrush = undo->brushlist.next; pBrush != NULL && pBrush != &undo->brushlist; pBrush = undo->brushlist.next )
	{
		//Sys_Printf("Owner ID: %i\n",pBrush->ownerId);
		g_undoMemorySize -= Brush_MemorySize( pBrush );
		Brush_RemoveFromList( pBrush );
		Brush_AddToList( pBrush, &active_brushes );
		for ( pEntity = entities.next; pEntity != NULL && pEntity != &entities; pEntity = pEntity->next ) // fixes broken undo on entities
		{
			//Sys_Printf("Entity ID: %i\n",pEntity->entityId);
			if ( pEntity->entityId == pBrush->ownerId ) {
				Entity_LinkBrush( pEntity, pBrush );
				break;
			}
		}
		//if the brush is not linked then it should be linked into the world entity
		//++timo FIXME: maybe not, maybe we've lost this entity's owner!
		if ( pEntity == NULL || pEntity == &entities ) {
			Entity_LinkBrush( world_entity, pBrush );
		}
		//build the brush
		//Brush_Build(pBrush);
		Select_Brush( pBrush );
		pBrush->redoId = redo->id;
	}
	if ( !bSilent ) {
		Sys_Printf( "%s undone.\n", undo->operation );
	}
	// free the undo
	g_undoMemorySize -= sizeof( undo_t );
	free( undo );
	g_undoSize--;
	g_undoId--;
	if ( g_undoId <= 0 ) {
		g_undoId = 2 * g_undoMaxSize;
	}
	//
	g_bScreenUpdates = true;
	UpdateSurfaceDialog();
	Sys_UpdateWindows( W_ALL );
}

/*
   =============
   Undo_Redo
   =============
 */
void Undo_Redo( void ){
	// spog - disable undo if undo levels = 0
	if ( g_PrefsDlg.m_nUndoLevels == 0 ) {
		Sys_Printf( "Undo_Redo: undo is disabled.\n" );
		return;
	}

	undo_t *redo;
	brush_t *pBrush, *pNextBrush;
	entity_t *pEntity, *pNextEntity, *pRedoEntity;

	if ( !g_lastredo ) {
		Sys_Printf( "Nothing left to redo.\n" );
		return;
	}
	if ( g_lastundo ) {
		if ( !g_lastundo->done ) {
			Sys_FPrintf( SYS_WRN, "WARNING: last undo not finished.\n" );
		}
	}
	// get the last redo
	redo = g_lastredo;
	if ( g_lastredo->prev ) {
		g_lastredo->prev->next = NULL;
	}
	else{g_redolist = NULL; }
	g_lastredo = g_lastredo->prev;
	//
	Undo_GeneralStart( redo->operation );
	// remove current selection
	Select_Deselect();
	// move "created" brushes back to the last undo
	for ( pBrush = active_brushes.next; pBrush != NULL && pBrush != &active_brushes; pBrush = pNextBrush )
	{
		pNextBrush = pBrush->next;
		if ( pBrush->redoId == redo->id ) {
			//move the brush to the undo
			Brush_RemoveFromList( pBrush );
			Brush_AddToList( pBrush, &g_lastundo->brushlist );
			g_undoMemorySize += Brush_MemorySize( pBrush );
			pBrush->ownerId = pBrush->owner->entityId;
			Entity_UnlinkBrush( pBrush );
		}
	}
	// move "created" entities back to the last undo
	for ( pEntity = entities.next; pEntity != NULL && pEntity != &entities; pEntity = pNextEntity )
	{
		pNextEntity = pEntity->next;
		if ( pEntity->redoId == redo->id ) {
			// check if this entity is in the redo
			for ( pRedoEntity = redo->entitylist.next; pRedoEntity != NULL && pRedoEntity != &redo->entitylist; pRedoEntity = pRedoEntity->next )
			{
				// move brushes to the redo entity
				if ( pRedoEntity->entityId == pEntity->entityId ) {
					pRedoEntity->brushes.next = pEntity->brushes.next;
					pRedoEntity->brushes.prev = pEntity->brushes.prev;
					pEntity->brushes.next = &pEntity->brushes;
					pEntity->brushes.prev = &pEntity->brushes;
				}
			}
			//
			//Entity_Free(pEntity);
			//move the entity to the redo
			Entity_RemoveFromList( pEntity );
			Entity_AddToList( pEntity, &g_lastundo->entitylist );
			g_undoMemorySize += Entity_MemorySize( pEntity );
		}
	}
	// add the undo entities back into the entity list
	for ( pEntity = redo->entitylist.next; pEntity != NULL && pEntity != &redo->entitylist; pEntity = redo->entitylist.next )
	{
		//if this is the world entity
		if ( pEntity->entityId == world_entity->entityId ) {
			epair_t* tmp = world_entity->epairs;
			world_entity->epairs = pEntity->epairs;
			pEntity->epairs = tmp;
			Entity_Free( pEntity );
		}
		else
		{
			Entity_RemoveFromList( pEntity );
			Entity_AddToList( pEntity, &entities );
		}
	}
	// add the redo brushes back into the selected brushes
	for ( pBrush = redo->brushlist.next; pBrush != NULL && pBrush != &redo->brushlist; pBrush = redo->brushlist.next )
	{
		Brush_RemoveFromList( pBrush );
		Brush_AddToList( pBrush, &active_brushes );
		for ( pEntity = entities.next; pEntity != NULL && pEntity != &entities; pEntity = pEntity->next ) // fixes broken undo on entities
		{
			if ( pEntity->entityId == pBrush->ownerId ) {
				Entity_LinkBrush( pEntity, pBrush );
				break;
			}
		}
		//if the brush is not linked then it should be linked into the world entity
		if ( pEntity == NULL || pEntity == &entities ) {
			Entity_LinkBrush( world_entity, pBrush );
		}
		//build the brush
		//Brush_Build(pBrush);
		Select_Brush( pBrush );
	}
	//
	Undo_End();
	//
	Sys_Printf( "%s redone.\n", redo->operation );
	//
	g_redoId--;
	// free the undo
	free( redo );
	//
	g_bScreenUpdates = true;
	UpdateSurfaceDialog();
	Sys_UpdateWindows( W_ALL );
}

/*
   =============
   Undo_RedoAvailable
   =============
 */
int Undo_RedoAvailable( void ){
	if ( g_lastredo ) {
		return true;
	}
	return false;
}

int Undo_GetUndoId( void ){
	if ( g_lastundo ) {
		return g_lastundo->id;
	}
	return 0;
}

/*
   =============
   Undo_UndoAvailable
   =============
 */
int Undo_UndoAvailable( void ){
	if ( g_lastundo ) {
		if ( g_lastundo->done ) {
			return true;
		}
	}
	return false;
}