Sound clip NLA Strips for Nexyon

[blender-staging.git] / source / blender / blenkernel / intern / nla.c

/*
 * $Id$
 *
 * ***** BEGIN GPL LICENSE BLOCK *****
 *
 * This program 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.
 *
 * This program 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 this program; if not, write to the Free Software Foundation,
 * Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.
 *
 * The Original Code is Copyright (C) 2009 Blender Foundation, Joshua Leung
 * All rights reserved.
 *
 * The Original Code is: all of this file.
 *
 * Contributor(s): Joshua Leung (full recode)
 *
 * ***** END GPL LICENSE BLOCK *****
 */

/** \file blender/blenkernel/intern/nla.c
 *  \ingroup bke
 */


#include <stdlib.h>
#include <stddef.h>
#include <stdio.h>
#include <string.h>
#include <math.h>
#include <float.h>

#include "MEM_guardedalloc.h"

#include "BLI_utildefines.h"
#include "BLI_ghash.h"

#include "DNA_anim_types.h"
#include "DNA_scene_types.h"
#include "DNA_sound_types.h"
#include "DNA_speaker_types.h"

#include "BKE_action.h"
#include "BKE_fcurve.h"
#include "BKE_nla.h"
#include "BKE_global.h"
#include "BKE_library.h"

#ifdef WITH_AUDASPACE
#  include "AUD_C-API.h"
#endif

#include "RNA_access.h"
#include "nla_private.h"



/* *************************************************** */
/* Data Management */

/* Freeing ------------------------------------------- */

/* Remove the given NLA strip from the NLA track it occupies, free the strip's data,
 * and the strip itself. 
 */
void free_nlastrip (ListBase *strips, NlaStrip *strip)
{
        NlaStrip *cs, *csn;
        
        /* sanity checks */
        if (strip == NULL)
                return;
                
        /* free child-strips */
        for (cs= strip->strips.first; cs; cs= csn) {
                csn= cs->next;
                free_nlastrip(&strip->strips, cs);
        }
                
        /* remove reference to action */
        if (strip->act)
                id_us_min(&strip->act->id);
                
        /* free remapping info */
        //if (strip->remap)
        //      BKE_animremap_free();
        
        /* free own F-Curves */
        free_fcurves(&strip->fcurves);
        
        /* free own F-Modifiers */
        free_fmodifiers(&strip->modifiers);
        
        /* free the strip itself */
        if (strips)
                BLI_freelinkN(strips, strip);
        else
                MEM_freeN(strip);
}

/* Remove the given NLA track from the set of NLA tracks, free the track's data,
 * and the track itself.
 */
void free_nlatrack (ListBase *tracks, NlaTrack *nlt)
{
        NlaStrip *strip, *stripn;
        
        /* sanity checks */
        if (nlt == NULL)
                return;
                
        /* free strips */
        for (strip= nlt->strips.first; strip; strip= stripn) {
                stripn= strip->next;
                free_nlastrip(&nlt->strips, strip);
        }
        
        /* free NLA track itself now */
        if (tracks)
                BLI_freelinkN(tracks, nlt);
        else
                MEM_freeN(nlt);
}

/* Free the elements of type NLA Tracks provided in the given list, but do not free
 * the list itself since that is not free-standing
 */
void free_nladata (ListBase *tracks)
{
        NlaTrack *nlt, *nltn;
        
        /* sanity checks */
        if ELEM(NULL, tracks, tracks->first)
                return;
                
        /* free tracks one by one */
        for (nlt= tracks->first; nlt; nlt= nltn) {
                nltn= nlt->next;
                free_nlatrack(tracks, nlt);
        }
        
        /* clear the list's pointers to be safe */
        tracks->first= tracks->last= NULL;
}

/* Copying ------------------------------------------- */

/* Copy NLA strip */
NlaStrip *copy_nlastrip (NlaStrip *strip)
{
        NlaStrip *strip_d;
        NlaStrip *cs, *cs_d;
        
        /* sanity check */
        if (strip == NULL)
                return NULL;
                
        /* make a copy */
        strip_d= MEM_dupallocN(strip);
        strip_d->next= strip_d->prev= NULL;
        
        /* increase user-count of action */
        if (strip_d->act)
                id_us_plus(&strip_d->act->id);
                
        /* copy F-Curves and modifiers */
        copy_fcurves(&strip_d->fcurves, &strip->fcurves);
        copy_fmodifiers(&strip_d->modifiers, &strip->modifiers);
        
        /* make a copy of all the child-strips, one at a time */
        strip_d->strips.first= strip_d->strips.last= NULL;
        
        for (cs= strip->strips.first; cs; cs= cs->next) {
                cs_d= copy_nlastrip(cs);
                BLI_addtail(&strip_d->strips, cs_d);
        }
        
        /* return the strip */
        return strip_d;
}

/* Copy NLA Track */
NlaTrack *copy_nlatrack (NlaTrack *nlt)
{
        NlaStrip *strip, *strip_d;
        NlaTrack *nlt_d;
        
        /* sanity check */
        if (nlt == NULL)
                return NULL;
                
        /* make a copy */
        nlt_d= MEM_dupallocN(nlt);
        nlt_d->next= nlt_d->prev= NULL;
        
        /* make a copy of all the strips, one at a time */
        nlt_d->strips.first= nlt_d->strips.last= NULL;
        
        for (strip= nlt->strips.first; strip; strip= strip->next) {
                strip_d= copy_nlastrip(strip);
                BLI_addtail(&nlt_d->strips, strip_d);
        }
        
        /* return the copy */
        return nlt_d;
}

/* Copy all NLA data */
void copy_nladata (ListBase *dst, ListBase *src)
{
        NlaTrack *nlt, *nlt_d;
        
        /* sanity checks */
        if ELEM(NULL, dst, src)
                return;
                
        /* clear out the destination list first for precautions... */
        dst->first= dst->last= NULL;
                
        /* copy each NLA-track, one at a time */
        for (nlt= src->first; nlt; nlt= nlt->next) {
                /* make a copy, and add the copy to the destination list */
                nlt_d= copy_nlatrack(nlt);
                BLI_addtail(dst, nlt_d);
        }
}

/* Adding ------------------------------------------- */

/* Add a NLA Track to the given AnimData 
 *      - prev: NLA-Track to add the new one after
 */
NlaTrack *add_nlatrack (AnimData *adt, NlaTrack *prev)
{
        NlaTrack *nlt;
        
        /* sanity checks */
        if (adt == NULL)
                return NULL;
                
        /* allocate new track */
        nlt= MEM_callocN(sizeof(NlaTrack), "NlaTrack");
        
        /* set settings requiring the track to not be part of the stack yet */
        nlt->flag = NLATRACK_SELECTED;
        nlt->index= BLI_countlist(&adt->nla_tracks);
        
        /* add track to stack, and make it the active one */
        if (prev)
                BLI_insertlinkafter(&adt->nla_tracks, prev, nlt);
        else
                BLI_addtail(&adt->nla_tracks, nlt);
        BKE_nlatrack_set_active(&adt->nla_tracks, nlt);
        
        /* must have unique name, but we need to seed this */
        strcpy(nlt->name, "NlaTrack");
        BLI_uniquename(&adt->nla_tracks, nlt, "NlaTrack", '.', offsetof(NlaTrack, name), sizeof(nlt->name));
        
        /* return the new track */
        return nlt;
}

/* Add a NLA Strip referencing the given Action */
NlaStrip *add_nlastrip (bAction *act)
{
        NlaStrip *strip;
        
        /* sanity checks */
        if (act == NULL)
                return NULL;
                
        /* allocate new strip */
        strip= MEM_callocN(sizeof(NlaStrip), "NlaStrip");
        
        /* generic settings 
         *      - selected flag to highlight this to the user
         *      - auto-blends to ensure that blend in/out values are automatically 
         *        determined by overlaps of strips
         *      - (XXX) synchronisation of strip-length in accordance with changes to action-length
         *        is not done though, since this should only really happens in editmode for strips now
         *        though this decision is still subject to further review...
         */
        strip->flag = NLASTRIP_FLAG_SELECT|NLASTRIP_FLAG_AUTO_BLENDS;
        
        /* assign the action reference */
        strip->act= act;
        id_us_plus(&act->id);
        
        /* determine initial range 
         *      - strip length cannot be 0... ever...
         */
        calc_action_range(strip->act, &strip->actstart, &strip->actend, 0);
        
        strip->start = strip->actstart;
        strip->end = (IS_EQF(strip->actstart, strip->actend)) ?  (strip->actstart + 1.0f): (strip->actend);
        
        /* strip should be referenced as-is */
        strip->scale= 1.0f;
        strip->repeat = 1.0f;
        
        /* return the new strip */
        return strip;
}

/* Add new NLA-strip to the top of the NLA stack - i.e. into the last track if space, or a new one otherwise */
NlaStrip *add_nlastrip_to_stack (AnimData *adt, bAction *act)
{
        NlaStrip *strip;
        NlaTrack *nlt;
        
        /* sanity checks */
        if ELEM(NULL, adt, act)
                return NULL;
        
        /* create a new NLA strip */
        strip= add_nlastrip(act);
        if (strip == NULL)
                return NULL;
        
        /* firstly try adding strip to last track, but if that fails, add to a new track */
        if (BKE_nlatrack_add_strip(adt->nla_tracks.last, strip) == 0) {
                /* trying to add to the last track failed (no track or no space), 
                 * so add a new track to the stack, and add to that...
                 */
                nlt= add_nlatrack(adt, NULL);
                BKE_nlatrack_add_strip(nlt, strip);
        }
        
        /* automatically name it too */
        BKE_nlastrip_validate_name(adt, strip);
        
        /* returns the strip added */
        return strip;
}

/* Add a NLA Strip referencing the given speaker's sound */
NlaStrip *add_nla_soundstrip (Scene *scene, Speaker *speaker)
{
        NlaStrip *strip = MEM_callocN(sizeof(NlaStrip), "NlaSoundStrip");
        
        /* if speaker has a sound, set the strip length to the length of the sound,
         * otherwise default to length of 10 frames
         */
#ifdef WITH_AUDASPACE
        if (speaker->sound) 
        {
                AUD_SoundInfo info = AUD_getInfo(speaker->sound->playback_handle);
                
                strip->end = ceil(info.length * FPS);
        }
        else 
#endif
        {
                strip->end = 10.0f;
        }
        
        /* general settings */
        strip->type = NLASTRIP_TYPE_SOUND;
        
        strip->flag = NLASTRIP_FLAG_SELECT;
        strip->extendmode = NLASTRIP_EXTEND_NOTHING; /* nothing to extend... */
        
        /* strip should be referenced as-is */
        strip->scale= 1.0f;
        strip->repeat = 1.0f;
        
        /* return this strip */
        return strip;
}

/* *************************************************** */
/* NLA Evaluation <-> Editing Stuff */

/* Strip Mapping ------------------------------------- */

/* non clipped mapping for strip-time <-> global time (for Action-Clips)
 *      invert = convert action-strip time to global time 
 */
static float nlastrip_get_frame_actionclip (NlaStrip *strip, float cframe, short mode)
{
        float actlength, scale;
        // float repeat; // UNUSED
        
        /* get number of repeats */
        if (IS_EQF(strip->repeat, 0.0f)) strip->repeat = 1.0f;
        // repeat = strip->repeat; // UNUSED
        
        /* scaling */
        if (IS_EQF(strip->scale, 0.0f)) strip->scale= 1.0f;
        scale = (float)fabs(strip->scale); /* scale must be positive - we've got a special flag for reversing */
        
        /* length of referenced action */
        actlength = strip->actend - strip->actstart;
        if (IS_EQF(actlength, 0.0f)) actlength = 1.0f;
        
        /* reversed = play strip backwards */
        if (strip->flag & NLASTRIP_FLAG_REVERSE) {
                // FIXME: this won't work right with Graph Editor?
                if (mode == NLATIME_CONVERT_MAP) {
                        return strip->end - scale*(cframe - strip->actstart);
                }
                else if (mode == NLATIME_CONVERT_UNMAP) {
                        return (strip->end + (strip->actstart * scale - cframe)) / scale;
                }
                else /* if (mode == NLATIME_CONVERT_EVAL) */{
                        if (IS_EQF(cframe, strip->end) && IS_EQF(strip->repeat, ((int)strip->repeat))) {
                                /* this case prevents the motion snapping back to the first frame at the end of the strip 
                                 * by catching the case where repeats is a whole number, which means that the end of the strip
                                 * could also be interpreted as the end of the start of a repeat
                                 */
                                return strip->actstart;
                        }
                        else {
                                /* - the 'fmod(..., actlength*scale)' is needed to get the repeats working
                                 * - the '/ scale' is needed to ensure that scaling influences the timing within the repeat
                                 */
                                return strip->actend - fmodf(cframe - strip->start, actlength*scale) / scale;
                        }
                }
        }
        else {
                if (mode == NLATIME_CONVERT_MAP) {
                        return strip->start + scale*(cframe - strip->actstart);
                }
                else if (mode == NLATIME_CONVERT_UNMAP) {
                        return strip->actstart + (cframe - strip->start) / scale;
                }
                else /* if (mode == NLATIME_CONVERT_EVAL) */{
                        if (IS_EQF(cframe, strip->end) && IS_EQF(strip->repeat, ((int)strip->repeat))) {
                                /* this case prevents the motion snapping back to the first frame at the end of the strip 
                                 * by catching the case where repeats is a whole number, which means that the end of the strip
                                 * could also be interpreted as the end of the start of a repeat
                                 */
                                return strip->actend;
                        }
                        else {
                                /* - the 'fmod(..., actlength*scale)' is needed to get the repeats working
                                 * - the '/ scale' is needed to ensure that scaling influences the timing within the repeat
                                 */
                                return strip->actstart + fmodf(cframe - strip->start, actlength*scale) / scale;
                        }
                }
        }
}

/* non clipped mapping for strip-time <-> global time (for Transitions)
 *      invert = convert action-strip time to global time 
 */
static float nlastrip_get_frame_transition (NlaStrip *strip, float cframe, short mode)
{
        float length;
        
        /* length of strip */
        length= strip->end - strip->start;
        
        /* reversed = play strip backwards */
        if (strip->flag & NLASTRIP_FLAG_REVERSE) {
                if (mode == NLATIME_CONVERT_MAP)
                        return strip->end - (length * cframe);
                else
                        return (strip->end - cframe) / length;
        }
        else {
                if (mode == NLATIME_CONVERT_MAP)
                        return (length * cframe) + strip->start;
                else
                        return (cframe - strip->start) / length;
        }
}

/* non clipped mapping for strip-time <-> global time
 *      mode = eNlaTime_ConvertModes[] -> NLATIME_CONVERT_*
 *
 * only secure for 'internal' (i.e. within AnimSys evaluation) operations,
 * but should not be directly relied on for stuff which interacts with editors
 */
float nlastrip_get_frame (NlaStrip *strip, float cframe, short mode)
{
        switch (strip->type) {
                case NLASTRIP_TYPE_META: /* meta - for now, does the same as transition (is really just an empty container) */
                case NLASTRIP_TYPE_TRANSITION: /* transition */
                        return nlastrip_get_frame_transition(strip, cframe, mode);
                
                case NLASTRIP_TYPE_CLIP: /* action-clip (default) */
                default:
                        return nlastrip_get_frame_actionclip(strip, cframe, mode);
        }       
}


/* Non clipped mapping for strip-time <-> global time
 *      mode = eNlaTime_ConvertModesp[] -> NLATIME_CONVERT_*
 *
 * Public API method - perform this mapping using the given AnimData block
 * and perform any necessary sanity checks on the value
 */
float BKE_nla_tweakedit_remap (AnimData *adt, float cframe, short mode)
{
        NlaStrip *strip;
        
        /* sanity checks 
         *      - obviously we've got to have some starting data
         *      - when not in tweakmode, the active Action does not have any scaling applied :)
         *      - when in tweakmode, if the no-mapping flag is set, do not map
         */
        if ((adt == NULL) || (adt->flag & ADT_NLA_EDIT_ON)==0 || (adt->flag & ADT_NLA_EDIT_NOMAP))
                return cframe;
                
        /* if the active-strip info has been stored already, access this, otherwise look this up
         * and store for (very probable) future usage
         */
        if (adt->actstrip == NULL) {
                NlaTrack *nlt= BKE_nlatrack_find_active(&adt->nla_tracks);
                adt->actstrip= BKE_nlastrip_find_active(nlt);
        }
        strip= adt->actstrip;
        
        /* sanity checks 
         *      - in rare cases, we may not be able to find this strip for some reason (internal error)
         *      - for now, if the user has defined a curve to control the time, this correction cannot be performed
         *        reliably...
         */
        if ((strip == NULL) || (strip->flag & NLASTRIP_FLAG_USR_TIME))
                return cframe;
                
        /* perform the correction now... */
        return nlastrip_get_frame(strip, cframe, mode);
}

/* *************************************************** */
/* NLA API */

/* List of Strips ------------------------------------ */
/* (these functions are used for NLA-Tracks and also for nested/meta-strips) */

/* Check if there is any space in the given list to add the given strip */
short BKE_nlastrips_has_space (ListBase *strips, float start, float end)
{
        NlaStrip *strip;
        
        /* sanity checks */
        if ((strips == NULL) || IS_EQF(start, end))
                return 0;
        if (start > end) {
                puts("BKE_nlastrips_has_space() error... start and end arguments swapped");
                SWAP(float, start, end);
        }
        
        /* loop over NLA strips checking for any overlaps with this area... */
        for (strip= strips->first; strip; strip= strip->next) {
                /* if start frame of strip is past the target end-frame, that means that
                 * we've gone past the window we need to check for, so things are fine
                 */
                if (strip->start >= end)
                        return 1;
                
                /* if the end of the strip is greater than either of the boundaries, the range
                 * must fall within the extents of the strip
                 */
                if ((strip->end > start) || (strip->end > end))
                        return 0;
        }
        
        /* if we are still here, we haven't encountered any overlapping strips */
        return 1;
}

/* Rearrange the strips in the track so that they are always in order 
 * (usually only needed after a strip has been moved) 
 */
void BKE_nlastrips_sort_strips (ListBase *strips)
{
        ListBase tmp = {NULL, NULL};
        NlaStrip *strip, *sstrip, *stripn;
        
        /* sanity checks */
        if ELEM(NULL, strips, strips->first)
                return;
        
        /* we simply perform insertion sort on this list, since it is assumed that per track,
         * there are only likely to be at most 5-10 strips
         */
        for (strip= strips->first; strip; strip= stripn) {
                short not_added = 1;
                
                stripn= strip->next;
                
                /* remove this strip from the list, and add it to the new list, searching from the end of 
                 * the list, assuming that the lists are in order 
                 */
                BLI_remlink(strips, strip);
                
                for (sstrip= tmp.last; sstrip; sstrip= sstrip->prev) {
                        /* check if add after */
                        if (sstrip->end <= strip->start) {
                                BLI_insertlinkafter(&tmp, sstrip, strip);
                                not_added= 0;
                                break;
                        }
                }
                
                /* add before first? */
                if (not_added)
                        BLI_addhead(&tmp, strip);
        }
        
        /* reassign the start and end points of the strips */
        strips->first= tmp.first;
        strips->last= tmp.last;
}

/* Add the given NLA-Strip to the given list of strips, assuming that it 
 * isn't currently a member of another list
 */
short BKE_nlastrips_add_strip (ListBase *strips, NlaStrip *strip)
{
        NlaStrip *ns;
        short not_added = 1;
        
        /* sanity checks */
        if ELEM(NULL, strips, strip)
                return 0;
                
        /* check if any space to add */
        if (BKE_nlastrips_has_space(strips, strip->start, strip->end)==0)
                return 0;
        
        /* find the right place to add the strip to the nominated track */
        for (ns= strips->first; ns; ns= ns->next) {
                /* if current strip occurs after the new strip, add it before */
                if (ns->start >= strip->end) {
                        BLI_insertlinkbefore(strips, ns, strip);
                        not_added= 0;
                        break;
                }
        }
        if (not_added) {
                /* just add to the end of the list of the strips then... */
                BLI_addtail(strips, strip);
        }
        
        /* added... */
        return 1;
}


/* Meta-Strips ------------------------------------ */

/* Convert 'islands' (i.e. continuous string of) selected strips to be
 * contained within 'Meta-Strips' which act as strips which contain strips.
 *      temp: are the meta-strips to be created 'temporary' ones used for transforms?
 */
void BKE_nlastrips_make_metas (ListBase *strips, short temp)
{
        NlaStrip *mstrip = NULL;
        NlaStrip *strip, *stripn;
        
        /* sanity checks */
        if ELEM(NULL, strips, strips->first)
                return;
        
        /* group all continuous chains of selected strips into meta-strips */
        for (strip= strips->first; strip; strip= stripn) {
                stripn= strip->next;
                
                if (strip->flag & NLASTRIP_FLAG_SELECT) {
                        /* if there is an existing meta-strip, add this strip to it, otherwise, create a new one */
                        if (mstrip == NULL) {
                                /* add a new meta-strip, and add it before the current strip that it will replace... */
                                mstrip= MEM_callocN(sizeof(NlaStrip), "Meta-NlaStrip");
                                mstrip->type = NLASTRIP_TYPE_META;
                                BLI_insertlinkbefore(strips, strip, mstrip);
                                
                                /* set flags */
                                mstrip->flag = NLASTRIP_FLAG_SELECT;
                                
                                /* set temp flag if appropriate (i.e. for transform-type editing) */
                                if (temp)
                                        mstrip->flag |= NLASTRIP_FLAG_TEMP_META;
                                        
                                /* set default repeat/scale values to prevent warnings */
                                mstrip->repeat= mstrip->scale= 1.0f;
                                
                                /* make its start frame be set to the start frame of the current strip */
                                mstrip->start= strip->start;
                        }
                        
                        /* remove the selected strips from the track, and add to the meta */
                        BLI_remlink(strips, strip);
                        BLI_addtail(&mstrip->strips, strip);
                        
                        /* expand the meta's dimensions to include the newly added strip- i.e. its last frame */
                        mstrip->end= strip->end;
                }
                else {
                        /* current strip wasn't selected, so the end of 'island' of selected strips has been reached,
                         * so stop adding strips to the current meta
                         */
                        mstrip= NULL;
                }
        }
}

/* Split a meta-strip into a set of normal strips */
void BKE_nlastrips_clear_metastrip (ListBase *strips, NlaStrip *strip)
{
        NlaStrip *cs, *csn;
        
        /* sanity check */
        if ELEM(NULL, strips, strip)
                return;
        
        /* move each one of the meta-strip's children before the meta-strip
         * in the list of strips after unlinking them from the meta-strip
         */
        for (cs= strip->strips.first; cs; cs= csn) {
                csn= cs->next;
                BLI_remlink(&strip->strips, cs);
                BLI_insertlinkbefore(strips, strip, cs);
        }
        
        /* free the meta-strip now */
        free_nlastrip(strips, strip);
}

/* Remove meta-strips (i.e. flatten the list of strips) from the top-level of the list of strips
 *      sel: only consider selected meta-strips, otherwise all meta-strips are removed
 *      onlyTemp: only remove the 'temporary' meta-strips used for transforms
 */
void BKE_nlastrips_clear_metas (ListBase *strips, short onlySel, short onlyTemp)
{
        NlaStrip *strip, *stripn;
        
        /* sanity checks */
        if ELEM(NULL, strips, strips->first)
                return;
        
        /* remove meta-strips fitting the criteria of the arguments */
        for (strip= strips->first; strip; strip= stripn) {
                stripn= strip->next;
                
                /* check if strip is a meta-strip */
                if (strip->type == NLASTRIP_TYPE_META) {
                        /* if check if selection and 'temporary-only' considerations are met */
                        if ((onlySel==0) || (strip->flag & NLASTRIP_FLAG_SELECT)) {
                                if ((!onlyTemp) || (strip->flag & NLASTRIP_FLAG_TEMP_META)) {
                                        BKE_nlastrips_clear_metastrip(strips, strip);
                                }
                        }
                }
        }
}

/* Add the given NLA-Strip to the given Meta-Strip, assuming that the
 * strip isn't attached to anyy list of strips 
 */
short BKE_nlameta_add_strip (NlaStrip *mstrip, NlaStrip *strip)
{
        /* sanity checks */
        if ELEM(NULL, mstrip, strip)
                return 0;
                
        /* firstly, check if the meta-strip has space for this */
        if (BKE_nlastrips_has_space(&mstrip->strips, strip->start, strip->end) == 0)
                return 0;
                
        /* check if this would need to be added to the ends of the meta,
         * and subsequently, if the neighbouring strips allow us enough room
         */
        if (strip->start < mstrip->start) {
                /* check if strip to the left (if it exists) ends before the 
                 * start of the strip we're trying to add 
                 */
                if ((mstrip->prev == NULL) || (mstrip->prev->end <= strip->start)) {
                        /* add strip to start of meta's list, and expand dimensions */
                        BLI_addhead(&mstrip->strips, strip);
                        mstrip->start= strip->start;
                        
                        return 1;
                }
                else /* failed... no room before */
                        return 0;
        }
        else if (strip->end > mstrip->end) {
                /* check if strip to the right (if it exists) starts before the 
                 * end of the strip we're trying to add 
                 */
                if ((mstrip->next == NULL) || (mstrip->next->start >= strip->end)) {
                        /* add strip to end of meta's list, and expand dimensions */
                        BLI_addtail(&mstrip->strips, strip);
                        mstrip->end= strip->end;
                        
                        return 1;
                }
                else /* failed... no room after */
                        return 0;
        }
        else {
                /* just try to add to the meta-strip (no dimension changes needed) */
                return BKE_nlastrips_add_strip(&mstrip->strips, strip);
        }
}

/* Adjust the settings of NLA-Strips contained within a Meta-Strip (recursively), 
 * until the Meta-Strips children all fit within the Meta-Strip's new dimensions
 */
void BKE_nlameta_flush_transforms (NlaStrip *mstrip) 
{
        NlaStrip *strip;
        float oStart, oEnd, offset;
        float oLen, nLen;
        short scaleChanged= 0;
        
        /* sanity checks 
         *      - strip must exist
         *      - strip must be a meta-strip with some contents
         */
        if ELEM(NULL, mstrip, mstrip->strips.first)
                return;
        if (mstrip->type != NLASTRIP_TYPE_META)
                return;
                
        /* get the original start/end points, and calculate the start-frame offset
         *      - these are simply the start/end frames of the child strips, 
         *        since we assume they weren't transformed yet
         */
        oStart= ((NlaStrip *)mstrip->strips.first)->start;
        oEnd= ((NlaStrip *)mstrip->strips.last)->end;
        offset= mstrip->start - oStart;
        
        /* optimisation:
         * don't flush if nothing changed yet
         *      TODO: maybe we need a flag to say always flush?
         */
        if (IS_EQF(oStart, mstrip->start) && IS_EQF(oEnd, mstrip->end))
                return;
        
        /* check if scale changed */
        oLen = oEnd - oStart;
        nLen = mstrip->end - mstrip->start;
        if (IS_EQF(nLen, oLen) == 0)
                scaleChanged= 1;
        
        /* for each child-strip, calculate new start/end points based on this new info */
        for (strip= mstrip->strips.first; strip; strip= strip->next) {
                if (scaleChanged) {
                        PointerRNA ptr;
                        float p1, p2, nStart, nEnd;
                        
                        /* compute positions of endpoints relative to old extents of strip */
                        p1= (strip->start - oStart) / oLen;
                        p2= (strip->end - oStart) / oLen;
                        
                        /* compute the new strip endpoints using the proportions */
                        nStart= (p1 * nLen) + mstrip->start;
                        nEnd= (p2 * nLen) + mstrip->start;
                        
                        /* firstly, apply the new positions manually, then apply using RNA 
                         *      - first time is to make sure no truncation errors from one endpoint not being 
                         *        set yet occur
                         *      - second time is to make sure scale is computed properly...
                         */
                        strip->start= nStart;
                        strip->end= nEnd;
                        
                        RNA_pointer_create(NULL, &RNA_NlaStrip, strip, &ptr);
                        RNA_float_set(&ptr, "frame_start", nStart);
                        RNA_float_set(&ptr, "frame_end", nEnd);
                }
                else {
                        /* just apply the changes in offset to both ends of the strip */
                        strip->start += offset;
                        strip->end += offset;
                }
                
                /* finally, make sure the strip's children (if it is a meta-itself), get updated */
                BKE_nlameta_flush_transforms(strip);
        }
}

/* NLA-Tracks ---------------------------------------- */

/* Find the active NLA-track for the given stack */
NlaTrack *BKE_nlatrack_find_active (ListBase *tracks)
{
        NlaTrack *nlt;
        
        /* sanity check */
        if ELEM(NULL, tracks, tracks->first)
                return NULL;
                
        /* try to find the first active track */
        for (nlt= tracks->first; nlt; nlt= nlt->next) {
                if (nlt->flag & NLATRACK_ACTIVE)
                        return nlt;
        }
        
        /* none found */
        return NULL;
}

/* Toggle the 'solo' setting for the given NLA-track, making sure that it is the only one
 * that has this status in its AnimData block.
 */
void BKE_nlatrack_solo_toggle (AnimData *adt, NlaTrack *nlt)
{
        NlaTrack *nt;
        
        /* sanity check */
        if ELEM(NULL, adt, adt->nla_tracks.first)
                return;
                
        /* firstly, make sure 'solo' flag for all tracks is disabled */
        for (nt= adt->nla_tracks.first; nt; nt= nt->next) {
                if (nt != nlt)
                        nt->flag &= ~NLATRACK_SOLO;
        }
                
        /* now, enable 'solo' for the given track if appropriate */
        if (nlt) {
                /* toggle solo status */
                nlt->flag ^= NLATRACK_SOLO;
                
                /* set or clear solo-status on AnimData */
                if (nlt->flag & NLATRACK_SOLO)
                        adt->flag |= ADT_NLA_SOLO_TRACK;
                else
                        adt->flag &= ~ADT_NLA_SOLO_TRACK;
        }
        else
                adt->flag &= ~ADT_NLA_SOLO_TRACK;
}

/* Make the given NLA-track the active one for the given stack. If no track is provided, 
 * this function can be used to simply deactivate all the NLA tracks in the given stack too.
 */
void BKE_nlatrack_set_active (ListBase *tracks, NlaTrack *nlt_a)
{
        NlaTrack *nlt;
        
        /* sanity check */
        if ELEM(NULL, tracks, tracks->first)
                return;
        
        /* deactive all the rest */
        for (nlt= tracks->first; nlt; nlt= nlt->next) 
                nlt->flag &= ~NLATRACK_ACTIVE;
                
        /* set the given one as the active one */
        if (nlt_a)
                nlt_a->flag |= NLATRACK_ACTIVE;
}

/* Check if there is any space in the given track to add a strip of the given length */
short BKE_nlatrack_has_space (NlaTrack *nlt, float start, float end)
{
        /* sanity checks 
         *      - track must exist
         *      - track must be editable
         *      - bounds cannot be equal (0-length is nasty) 
         */
        if ((nlt == NULL) || (nlt->flag & NLATRACK_PROTECTED) || IS_EQF(start, end))
                return 0;
        
        if (start > end) {
                puts("BKE_nlatrack_has_space() error... start and end arguments swapped");
                SWAP(float, start, end);
        }
        
        /* check if there's any space left in the track for a strip of the given length */
        return BKE_nlastrips_has_space(&nlt->strips, start, end);
}

/* Rearrange the strips in the track so that they are always in order 
 * (usually only needed after a strip has been moved) 
 */
void BKE_nlatrack_sort_strips (NlaTrack *nlt)
{
        /* sanity checks */
        if ELEM(NULL, nlt, nlt->strips.first)
                return;
        
        /* sort the strips with a more generic function */
        BKE_nlastrips_sort_strips(&nlt->strips);
}

/* Add the given NLA-Strip to the given NLA-Track, assuming that it 
 * isn't currently attached to another one 
 */
short BKE_nlatrack_add_strip (NlaTrack *nlt, NlaStrip *strip)
{
        /* sanity checks */
        if ELEM(NULL, nlt, strip)
                return 0;
                
        /* try to add the strip to the track using a more generic function */
        return BKE_nlastrips_add_strip(&nlt->strips, strip);
}

/* Get the extents of the given NLA-Track including gaps between strips,
 * returning whether this succeeded or not
 */
short BKE_nlatrack_get_bounds (NlaTrack *nlt, float bounds[2])
{
        NlaStrip *strip;
        
        /* initialise bounds */
        if (bounds)
                bounds[0] = bounds[1] = 0.0f;
        else
                return 0;
        
        /* sanity checks */
        if ELEM(NULL, nlt, nlt->strips.first)
                return 0;
                
        /* lower bound is first strip's start frame */
        strip = nlt->strips.first;
        bounds[0] = strip->start;
        
        /* upper bound is last strip's end frame */
        strip = nlt->strips.last;
        bounds[1] = strip->end;
        
        /* done */
        return 1;
}

/* NLA Strips -------------------------------------- */

/* Find the active NLA-strip within the given track */
NlaStrip *BKE_nlastrip_find_active (NlaTrack *nlt)
{
        NlaStrip *strip;
        
        /* sanity check */
        if ELEM(NULL, nlt, nlt->strips.first)
                return NULL;
                
        /* try to find the first active strip */
        for (strip= nlt->strips.first; strip; strip= strip->next) {
                if (strip->flag & NLASTRIP_FLAG_ACTIVE)
                        return strip;
        }
        
        /* none found */
        return NULL;
}

/* Make the given NLA-Strip the active one within the given block */
void BKE_nlastrip_set_active (AnimData *adt, NlaStrip *strip)
{
        NlaTrack *nlt;
        NlaStrip *nls;
        
        /* sanity checks */
        if (adt == NULL)
                return;
        
        /* loop over tracks, deactivating*/
        for (nlt= adt->nla_tracks.first; nlt; nlt= nlt->next) {
                for (nls= nlt->strips.first; nls; nls= nls->next)  {
                        if (nls != strip)
                                nls->flag &= ~NLASTRIP_FLAG_ACTIVE;
                        else
                                nls->flag |= NLASTRIP_FLAG_ACTIVE;
                }
        }
}


/* Does the given NLA-strip fall within the given bounds (times)? */
short BKE_nlastrip_within_bounds (NlaStrip *strip, float min, float max)
{
        const float stripLen= (strip) ? strip->end - strip->start : 0.0f;
        const float boundsLen= (float)fabs(max - min);
        
        /* sanity checks */
        if ((strip == NULL) || IS_EQF(stripLen, 0.0f) || IS_EQF(boundsLen, 0.0f))
                return 0;
        
        /* only ok if at least part of the strip is within the bounding window
         *      - first 2 cases cover when the strip length is less than the bounding area
         *      - second 2 cases cover when the strip length is greater than the bounding area
         */
        if ( (stripLen < boundsLen) && 
                 !(IN_RANGE(strip->start, min, max) ||
                   IN_RANGE(strip->end, min, max)) )
        {
                return 0;
        }
        if ( (stripLen > boundsLen) && 
                 !(IN_RANGE(min, strip->start, strip->end) ||
                   IN_RANGE(max, strip->start, strip->end)) )
        {
                return 0;
        }
        
        /* should be ok! */
        return 1;
}

/* Recalculate the start and end frames for the current strip, after changing
 * the extents of the action or the mapping (repeats or scale factor) info
 */
void BKE_nlastrip_recalculate_bounds (NlaStrip *strip)
{
        float actlen, mapping;
        
        /* sanity checks
         *      - must have a strip
         *      - can only be done for action clips
         */
        if ((strip == NULL) || (strip->type != NLASTRIP_TYPE_CLIP))
                return;
                
        /* calculate new length factors */
        actlen= strip->actend - strip->actstart;
        if (IS_EQF(actlen, 0.0f)) actlen= 1.0f;
        
        mapping= strip->scale * strip->repeat;
        
        /* adjust endpoint of strip in response to this */
        if (IS_EQF(mapping, 0.0f) == 0)
                strip->end = (actlen * mapping) + strip->start;
}

/* Is the given NLA-strip the first one to occur for the given AnimData block */
// TODO: make this an api method if necesary, but need to add prefix first
static short nlastrip_is_first (AnimData *adt, NlaStrip *strip)
{
        NlaTrack *nlt;
        NlaStrip *ns;
        
        /* sanity checks */
        if ELEM(NULL, adt, strip)
                return 0;
                
        /* check if strip has any strips before it */
        if (strip->prev)
                return 0;
                
        /* check other tracks to see if they have a strip that's earlier */
        // TODO: or should we check that the strip's track is also the first?
        for (nlt= adt->nla_tracks.first; nlt; nlt= nlt->next) {
                /* only check the first strip, assuming that they're all in order */
                ns= nlt->strips.first;
                if (ns) {
                        if (ns->start < strip->start)
                                return 0;
                }
        }       
        
        /* should be first now */
        return 1;
}

/* Animated Strips ------------------------------------------- */

/* Check if the given NLA-Track has any strips with own F-Curves */
short BKE_nlatrack_has_animated_strips (NlaTrack *nlt)
{
        NlaStrip *strip;
        
        /* sanity checks */
        if ELEM(NULL, nlt, nlt->strips.first)
                return 0;
                
        /* check each strip for F-Curves only (don't care about whether the flags are set) */
        for (strip= nlt->strips.first; strip; strip= strip->next) {
                if (strip->fcurves.first)
                        return 1;
        }
        
        /* none found */
        return 0;
}

/* Check if given NLA-Tracks have any strips with own F-Curves */
short BKE_nlatracks_have_animated_strips (ListBase *tracks)
{
        NlaTrack *nlt;
        
        /* sanity checks */
        if ELEM(NULL, tracks, tracks->first)
                return 0;
                
        /* check each track, stopping on the first hit */
        for (nlt= tracks->first; nlt; nlt= nlt->next) {
                if (BKE_nlatrack_has_animated_strips(nlt))
                        return 1;
        }
        
        /* none found */
        return 0;
}

/* Validate the NLA-Strips 'control' F-Curves based on the flags set*/
void BKE_nlastrip_validate_fcurves (NlaStrip *strip) 
{
        FCurve *fcu;
        
        /* sanity checks */
        if (strip == NULL)
                return;
        
        /* if controlling influence... */
        if (strip->flag & NLASTRIP_FLAG_USR_INFLUENCE) {
                /* try to get F-Curve */
                fcu= list_find_fcurve(&strip->fcurves, "influence", 0);
                
                /* add one if not found */
                if (fcu == NULL) {
                        /* make new F-Curve */
                        fcu= MEM_callocN(sizeof(FCurve), "NlaStrip FCurve");
                        BLI_addtail(&strip->fcurves, fcu);
                        
                        /* set default flags */
                        fcu->flag = (FCURVE_VISIBLE|FCURVE_SELECTED);
                        
                        /* store path - make copy, and store that */
                        fcu->rna_path= BLI_strdupn("influence", 9);
                        
                        // TODO: insert a few keyframes to ensure default behaviour?
                }
        }
        
        /* if controlling time... */
        if (strip->flag & NLASTRIP_FLAG_USR_TIME) {
                /* try to get F-Curve */
                fcu= list_find_fcurve(&strip->fcurves, "strip_time", 0);
                
                /* add one if not found */
                if (fcu == NULL) {
                        /* make new F-Curve */
                        fcu= MEM_callocN(sizeof(FCurve), "NlaStrip FCurve");
                        BLI_addtail(&strip->fcurves, fcu);
                        
                        /* set default flags */
                        fcu->flag = (FCURVE_VISIBLE|FCURVE_SELECTED);
                        
                        /* store path - make copy, and store that */
                        fcu->rna_path= BLI_strdupn("strip_time", 10);
                        
                        // TODO: insert a few keyframes to ensure default behaviour?
                }
        }
}

/* Sanity Validation ------------------------------------ */

static int nla_editbone_name_check(void *arg, const char *name)
{
        return BLI_ghash_haskey((GHash *)arg, (void *)name);
}

/* Find (and set) a unique name for a strip from the whole AnimData block 
 * Uses a similar method to the BLI method, but is implemented differently
 * as we need to ensure that the name is unique over several lists of tracks,
 * not just a single track.
 */
void BKE_nlastrip_validate_name (AnimData *adt, NlaStrip *strip)
{
        GHash *gh;
        NlaStrip *tstrip;
        NlaTrack *nlt;
        
        /* sanity checks */
        if ELEM(NULL, adt, strip)
                return;
                
        /* give strip a default name if none already */
        if (strip->name[0]==0) {
                switch (strip->type) {
                        case NLASTRIP_TYPE_CLIP: /* act-clip */
                                sprintf(strip->name, "%s", (strip->act)?(strip->act->id.name+2):("<No Action>"));
                                break;
                        case NLASTRIP_TYPE_TRANSITION: /* transition */
                                sprintf(strip->name, "Transition");
                                break;
                        case NLASTRIP_TYPE_META: /* meta */
                                sprintf(strip->name, "Meta");
                                break;
                        default:
                                sprintf(strip->name, "NLA Strip");
                                break;
                }
        }
        
        /* build a hash-table of all the strips in the tracks 
         *      - this is easier than iterating over all the tracks+strips hierarchy everytime
         *        (and probably faster)
         */
        gh= BLI_ghash_new(BLI_ghashutil_strhash, BLI_ghashutil_strcmp, "nlastrip_validate_name gh");
        
        for (nlt= adt->nla_tracks.first; nlt; nlt= nlt->next) {
                for (tstrip= nlt->strips.first; tstrip; tstrip= tstrip->next) {
                        /* don't add the strip of interest */
                        if (tstrip == strip) 
                                continue;
                        
                        /* use the name of the strip as the key, and the strip as the value, since we're mostly interested in the keys */
                        BLI_ghash_insert(gh, tstrip->name, tstrip);
                }
        }
        
        /* if the hash-table has a match for this name, try other names... 
         *      - in an extreme case, it might not be able to find a name, but then everything else in Blender would fail too :)
         */
        BLI_uniquename_cb(nla_editbone_name_check, (void *)gh, "NlaStrip", '.', strip->name, sizeof(strip->name));

        /* free the hash... */
        BLI_ghash_free(gh, NULL, NULL);
}

/* ---- */

/* Get strips which overlap the given one at the start/end of its range 
 *      - strip: strip that we're finding overlaps for
 *      - track: nla-track that the overlapping strips should be found from
 *      - start, end: frames for the offending endpoints
 */
static void nlastrip_get_endpoint_overlaps (NlaStrip *strip, NlaTrack *track, float **start, float **end)
{
        NlaStrip *nls;
        
        /* find strips that overlap over the start/end of the given strip,
         * but which don't cover the entire length 
         */
        // TODO: this scheme could get quite slow for doing this on many strips...
        for (nls= track->strips.first; nls; nls= nls->next) {
                /* check if strip overlaps (extends over or exactly on) the entire range of the strip we're validating */
                if ((nls->start <= strip->start) && (nls->end >= strip->end)) {
                        *start= NULL;
                        *end= NULL;
                        return;
                }
                
                /* check if strip doesn't even occur anywhere near... */
                if (nls->end < strip->start)
                        continue; /* skip checking this strip... not worthy of mention */
                if (nls->start > strip->end)
                        return; /* the range we're after has already passed */
                        
                /* if this strip is not part of an island of continuous strips, it can be used
                 *      - this check needs to be done for each end of the strip we try and use...
                 */
                if ((nls->next == NULL) || IS_EQF(nls->next->start, nls->end)==0) {
                        if ((nls->end > strip->start) && (nls->end < strip->end))
                                *start= &nls->end;
                }
                if ((nls->prev == NULL) || IS_EQF(nls->prev->end, nls->start)==0) {
                        if ((nls->start < strip->end) && (nls->start > strip->start))
                                *end= &nls->start;
                }
        }
}

/* Determine auto-blending for the given strip */
static void BKE_nlastrip_validate_autoblends (NlaTrack *nlt, NlaStrip *nls)
{
        float *ps=NULL, *pe=NULL;
        float *ns=NULL, *ne=NULL;
        
        /* sanity checks */
        if ELEM(NULL, nls, nlt)
                return;
        if ((nlt->prev == NULL) && (nlt->next == NULL))
                return;
        if ((nls->flag & NLASTRIP_FLAG_AUTO_BLENDS)==0)
                return;
        
        /* get test ranges */
        if (nlt->prev)
                nlastrip_get_endpoint_overlaps(nls, nlt->prev, &ps, &pe);
        if (nlt->next)
                nlastrip_get_endpoint_overlaps(nls, nlt->next, &ns, &ne);
                
        /* set overlaps for this strip 
         *      - don't use the values obtained though if the end in question 
         *        is directly followed/preceeded by another strip, forming an 
         *        'island' of continuous strips
         */
        if ( (ps || ns) && ((nls->prev == NULL) || IS_EQF(nls->prev->end, nls->start)==0) )
        {
                /* start overlaps - pick the largest overlap */
                if ( ((ps && ns) && (*ps > *ns)) || (ps) )
                        nls->blendin= *ps - nls->start;
                else
                        nls->blendin= *ns - nls->start;
        }
        else /* no overlap allowed/needed */
                nls->blendin= 0.0f;
                
        if ( (pe || ne) && ((nls->next == NULL) || IS_EQF(nls->next->start, nls->end)==0) )
        {
                /* end overlaps - pick the largest overlap */
                if ( ((pe && ne) && (*pe > *ne)) || (pe) )
                        nls->blendout= nls->end - *pe;
                else
                        nls->blendout= nls->end - *ne;
        }
        else /* no overlap allowed/needed */
                nls->blendout= 0.0f;
}

/* Ensure that auto-blending and other settings are set correctly */
void BKE_nla_validate_state (AnimData *adt)
{
        NlaStrip *strip, *fstrip=NULL;
        NlaTrack *nlt;
        
        /* sanity checks */
        if ELEM(NULL, adt, adt->nla_tracks.first)
                return;
                
        /* adjust blending values for auto-blending, and also do an initial pass to find the earliest strip */
        for (nlt= adt->nla_tracks.first; nlt; nlt= nlt->next) {
                for (strip= nlt->strips.first; strip; strip= strip->next) {
                        /* auto-blending first */
                        BKE_nlastrip_validate_autoblends(nlt, strip);
                        
                        /* extend mode - find first strip */
                        if ((fstrip == NULL) || (strip->start < fstrip->start))
                                fstrip= strip;
                }
        }
        
        /* second pass over the strips to adjust the extend-mode to fix any problems */
        for (nlt= adt->nla_tracks.first; nlt; nlt= nlt->next) {
                for (strip= nlt->strips.first; strip; strip= strip->next) {
                        /* apart from 'nothing' option which user has to explicitly choose, we don't really know if 
                         * we should be overwriting the extend setting (but assume that's what the user wanted)
                         */
                        // TODO: 1 solution is to tie this in with auto-blending...
                        if (strip->extendmode != NLASTRIP_EXTEND_NOTHING) {
                                if (strip == fstrip)
                                        strip->extendmode= NLASTRIP_EXTEND_HOLD;
                                else
                                        strip->extendmode= NLASTRIP_EXTEND_HOLD_FORWARD;
                        }
                }
        }
}

/* Core Tools ------------------------------------------- */

/* For the given AnimData block, add the active action to the NLA
 * stack (i.e. 'push-down' action). The UI should only allow this 
 * for normal editing only (i.e. not in editmode for some strip's action),
 * so no checks for this are performed.
 */
// TODO: maybe we should have checks for this too...
void BKE_nla_action_pushdown (AnimData *adt)
{
        NlaStrip *strip;
        
        /* sanity checks */
        // TODO: need to report the error for this
        if ELEM(NULL, adt, adt->action) 
                return;
                
        /* if the action is empty, we also shouldn't try to add to stack, 
         * as that will cause us grief down the track
         */
        // TODO: what about modifiers?
        if (action_has_motion(adt->action) == 0) {
                printf("BKE_nla_action_pushdown(): action has no data \n");
                return;
        }
        
        /* add a new NLA strip to the track, which references the active action */
        strip= add_nlastrip_to_stack(adt, adt->action);
        
        /* do other necessary work on strip */  
        if (strip) {
                /* clear reference to action now that we've pushed it onto the stack */
                id_us_min(&adt->action->id);
                adt->action= NULL;
                
                /* if the strip is the first one in the track it lives in, check if there
                 * are strips in any other tracks that may be before this, and set the extend
                 * mode accordingly
                 */
                if (nlastrip_is_first(adt, strip) == 0) {
                        /* not first, so extend mode can only be NLASTRIP_EXTEND_HOLD_FORWARD not NLASTRIP_EXTEND_HOLD,
                         * so that it doesn't override strips in previous tracks
                         */
                        // FIXME: this needs to be more automated, since user can rearrange strips
                        strip->extendmode= NLASTRIP_EXTEND_HOLD_FORWARD;
                }
                
                /* make strip the active one... */
                BKE_nlastrip_set_active(adt, strip);
        }
}


/* Find the active strip + track combo, and set them up as the tweaking track,
 * and return if successful or not.
 */
short BKE_nla_tweakmode_enter (AnimData *adt)
{
        NlaTrack *nlt, *activeTrack=NULL;
        NlaStrip *strip, *activeStrip=NULL;
        
        /* verify that data is valid */
        if ELEM(NULL, adt, adt->nla_tracks.first)
                return 0;
                
        /* if block is already in tweakmode, just leave, but we should report 
         * that this block is in tweakmode (as our returncode)
         */
        if (adt->flag & ADT_NLA_EDIT_ON)
                return 1;
                
        /* go over the tracks, finding the active one, and its active strip
         *      - if we cannot find both, then there's nothing to do
         */
        for (nlt= adt->nla_tracks.first; nlt; nlt= nlt->next) {
                /* check if active */
                if (nlt->flag & NLATRACK_ACTIVE) {
                        /* store reference to this active track */
                        activeTrack= nlt;
                        
                        /* now try to find active strip */
                        activeStrip= BKE_nlastrip_find_active(nlt);
                        break;
                }       
        }
        if ELEM3(NULL, activeTrack, activeStrip, activeStrip->act) {
                if (G.f & G_DEBUG) {
                        printf("NLA tweakmode enter - neither active requirement found \n");
                        printf("\tactiveTrack = %p, activeStrip = %p \n", (void *)activeTrack, (void *)activeStrip);
                }
                return 0;
        }
                
        /* go over all the tracks up to the active one, tagging each strip that uses the same 
         * action as the active strip, but leaving everything else alone
         */
        for (nlt= activeTrack->prev; nlt; nlt= nlt->prev) {
                for (strip= nlt->strips.first; strip; strip= strip->next) {
                        if (strip->act == activeStrip->act)
                                strip->flag |= NLASTRIP_FLAG_TWEAKUSER;
                        else
                                strip->flag &= ~NLASTRIP_FLAG_TWEAKUSER;
                }
        }
        
        
        /* go over all the tracks after AND INCLUDING the active one, tagging them as being disabled 
         *      - the active track needs to also be tagged, otherwise, it'll overlap with the tweaks going on
         */
        for (nlt= activeTrack; nlt; nlt= nlt->next)
                nlt->flag |= NLATRACK_DISABLED;
        
        /* handle AnimData level changes:
         *      - 'real' active action to temp storage (no need to change user-counts)
         *      - action of active strip set to be the 'active action', and have its usercount incremented
         *      - editing-flag for this AnimData block should also get turned on (for more efficient restoring)
         *      - take note of the active strip for mapping-correction of keyframes in the action being edited
         */
        adt->tmpact= adt->action;
        adt->action= activeStrip->act;
        adt->actstrip= activeStrip;
        id_us_plus(&activeStrip->act->id);
        adt->flag |= ADT_NLA_EDIT_ON;
        
        /* done! */
        return 1;
}

/* Exit tweakmode for this AnimData block */
void BKE_nla_tweakmode_exit (AnimData *adt)
{
        NlaStrip *strip;
        NlaTrack *nlt;
        
        /* verify that data is valid */
        if ELEM(NULL, adt, adt->nla_tracks.first)
                return;
                
        /* hopefully the flag is correct - skip if not on */
        if ((adt->flag & ADT_NLA_EDIT_ON) == 0)
                return;
                
        // TODO: need to sync the user-strip with the new state of the action!
                
        /* for all Tracks, clear the 'disabled' flag
         * for all Strips, clear the 'tweak-user' flag
         */
        for (nlt= adt->nla_tracks.first; nlt; nlt= nlt->next) {
                nlt->flag &= ~NLATRACK_DISABLED;
                
                for (strip= nlt->strips.first; strip; strip= strip->next) 
                        strip->flag &= ~NLASTRIP_FLAG_TWEAKUSER;
        }
        
        /* handle AnimData level changes:
         *      - 'temporary' active action needs its usercount decreased, since we're removing this reference
         *      - 'real' active action is restored from storage
         *      - storage pointer gets cleared (to avoid having bad notes hanging around)
         *      - editing-flag for this AnimData block should also get turned off
         *      - clear pointer to active strip
         */
        if (adt->action) adt->action->id.us--;
        adt->action= adt->tmpact;
        adt->tmpact= NULL;
        adt->actstrip= NULL;
        adt->flag &= ~ADT_NLA_EDIT_ON;
}

/* Baking Tools ------------------------------------------- */

static void BKE_nla_bake (Scene *scene, ID *UNUSED(id), AnimData *adt, int UNUSED(flag))
{

        /* verify that data is valid 
         *      1) Scene and AnimData must be provided 
         *      2) there must be tracks to merge...
         */
        if ELEM3(NULL, scene, adt, adt->nla_tracks.first)
                return;
        
        /* if animdata currently has an action, 'push down' this onto the stack first */
        if (adt->action)
                BKE_nla_action_pushdown(adt);
        
        /* get range of motion to bake, and the channels involved... */
        
        /* temporarily mute the action, and start keying to it */
        
        /* start keying... */
        
        /* unmute the action */
}

/* *************************************************** */