/*
 * ***** 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.
 *
 * 
 * Contributor(s): Joshua Leung (major recode)
 *
 * ***** END GPL LICENSE BLOCK *****
 */

/** \file blender/editors/space_nla/nla_draw.c
 *  \ingroup spnla
 */


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

#include "DNA_anim_types.h"
#include "DNA_node_types.h"
#include "DNA_screen_types.h"
#include "DNA_space_types.h"
#include "DNA_windowmanager_types.h"

#include "BLI_blenlib.h"
#include "BLI_dlrbTree.h"
#include "BLI_utildefines.h"

#include "BKE_fcurve.h"
#include "BKE_nla.h"
#include "BKE_context.h"
#include "BKE_screen.h"

#include "ED_anim_api.h"
#include "ED_keyframes_draw.h"

#include "BIF_gl.h"
#include "BIF_glutil.h"

#include "WM_types.h"

#include "UI_interface.h"
#include "UI_interface_icons.h"
#include "UI_resources.h"
#include "UI_view2d.h"


#include "nla_intern.h" /* own include */


/* *********************************************** */
/* Strips */

/* Action-Line ---------------------- */

/* get colors for drawing Action-Line 
 * NOTE: color returned includes fine-tuned alpha!
 */
void nla_action_get_color(AnimData *adt, bAction *act, float color[4])
{
	if (adt && (adt->flag & ADT_NLA_EDIT_ON)) {
		/* greenish color (same as tweaking strip) */
		UI_GetThemeColor4fv(TH_NLA_TWEAK, color);
	}
	else {
		if (act) {
			/* reddish color - same as dopesheet summary */
			UI_GetThemeColor4fv(TH_ANIM_ACTIVE, color);
		}
		else {
			/* grayish-red color */
			UI_GetThemeColor4fv(TH_ANIM_INACTIVE, color);
		}
	}
	
	/* when an NLA track is tagged "solo", action doesn't contribute, so shouldn't be as prominent */
	if (adt && (adt->flag & ADT_NLA_SOLO_TRACK))
		color[3] *= 0.15f;
}

/* draw the keyframes in the specified Action */
static void nla_action_draw_keyframes(AnimData *adt, bAction *act, View2D *v2d, float y, float ymin, float ymax)
{
	DLRBT_Tree keys;
	ActKeyColumn *ak;
	float xscale, f1, f2;
	float color[4];
	
	/* get a list of the keyframes with NLA-scaling applied */
	BLI_dlrbTree_init(&keys);
	action_to_keylist(adt, act, &keys, NULL);
	BLI_dlrbTree_linkedlist_sync(&keys);
	
	if (ELEM(NULL, act, keys.first))
		return;
	
	/* draw a darkened region behind the strips 
	 *	- get and reset the background color, this time without the alpha to stand out better 
	 *	  (amplified alpha is used instead)
	 */
	nla_action_get_color(adt, act, color);
	color[3] *= 2.5f;
	
	glColor4fv(color);
	/*  - draw a rect from the first to the last frame (no extra overlaps for now)
	 *	  that is slightly stumpier than the track background (hardcoded 2-units here)
	 */
	f1 = ((ActKeyColumn *)keys.first)->cfra;
	f2 = ((ActKeyColumn *)keys.last)->cfra;
	
	glRectf(f1, ymin + 2, f2, ymax - 2);
	
	
	/* get View2D scaling factor */
	UI_view2d_scale_get(v2d, &xscale, NULL);
	
	/* for now, color is hardcoded to be black */
	glColor3f(0.0f, 0.0f, 0.0f);
	
	/* just draw each keyframe as a simple dot (regardless of the selection status) 
	 *	- size is 3.0f which is smaller than the editable keyframes, so that there is a distinction
	 */
	for (ak = keys.first; ak; ak = ak->next)
		draw_keyframe_shape(ak->cfra, y, xscale, 3.0f, 0, ak->key_type, KEYFRAME_SHAPE_FRAME, 1.0f);
	
	/* free icons */
	BLI_dlrbTree_free(&keys);
}

/* Strips (Proper) ---------------------- */

/* get colors for drawing NLA-Strips */
static void nla_strip_get_color_inside(AnimData *adt, NlaStrip *strip, float color[3])
{
	if (strip->type == NLASTRIP_TYPE_TRANSITION) {
		/* Transition Clip */
		if (strip->flag & NLASTRIP_FLAG_SELECT) {
			/* selected - use a bright blue color */
			UI_GetThemeColor3fv(TH_NLA_TRANSITION_SEL, color);
		}
		else {
			/* normal, unselected strip - use (hardly noticeable) blue tinge */
			UI_GetThemeColor3fv(TH_NLA_TRANSITION, color);
		}
	}
	else if (strip->type == NLASTRIP_TYPE_META) {
		/* Meta Clip */
		// TODO: should temporary metas get different colors too?
		if (strip->flag & NLASTRIP_FLAG_SELECT) {
			/* selected - use a bold purple color */
			UI_GetThemeColor3fv(TH_NLA_META_SEL, color);
		}
		else {
			/* normal, unselected strip - use (hardly noticeable) dark purple tinge */
			UI_GetThemeColor3fv(TH_NLA_META, color);
		}
	}
	else if (strip->type == NLASTRIP_TYPE_SOUND) {
		/* Sound Clip */
		if (strip->flag & NLASTRIP_FLAG_SELECT) {
			/* selected - use a bright teal color */
			UI_GetThemeColor3fv(TH_NLA_SOUND_SEL, color);
		}
		else {
			/* normal, unselected strip - use (hardly noticeable) teal tinge */
			UI_GetThemeColor3fv(TH_NLA_SOUND, color);
		}
	}
	else {
		/* Action Clip (default/normal type of strip) */
		if ((strip->flag & NLASTRIP_FLAG_ACTIVE) && (adt && (adt->flag & ADT_NLA_EDIT_ON))) {
			/* active strip should be drawn green when it is acting as the tweaking strip.
			 * however, this case should be skipped for when not in EditMode...
			 */
			UI_GetThemeColor3fv(TH_NLA_TWEAK, color);
		}
		else if (strip->flag & NLASTRIP_FLAG_TWEAKUSER) {
			/* alert user that this strip is also used by the tweaking track (this is set when going into
			 * 'editmode' for that strip), since the edits made here may not be what the user anticipated
			 */
			UI_GetThemeColor3fv(TH_NLA_TWEAK_DUPLI, color);
		}
		else if (strip->flag & NLASTRIP_FLAG_SELECT) {
			/* selected strip - use theme color for selected */
			UI_GetThemeColor3fv(TH_STRIP_SELECT, color);
		}
		else {
			/* normal, unselected strip - use standard strip theme color */
			UI_GetThemeColor3fv(TH_STRIP, color);
		}
	}
}

/* helper call for drawing influence/time control curves for a given NLA-strip */
static void nla_draw_strip_curves(NlaStrip *strip, float yminc, float ymaxc)
{
	const float yheight = ymaxc - yminc;
	
	/* drawing color is simply a light-gray */
	// TODO: is this color suitable?
	// XXX nasty hacked color for now... which looks quite bad too...
	glColor3f(0.7f, 0.7f, 0.7f);
	
	/* draw with AA'd line */
	glEnable(GL_LINE_SMOOTH);
	glEnable(GL_BLEND);
	
	/* influence -------------------------- */
	if (strip->flag & NLASTRIP_FLAG_USR_INFLUENCE) {
		FCurve *fcu = list_find_fcurve(&strip->fcurves, "influence", 0);
		float cfra;
		
		/* plot the curve (over the strip's main region) */
		glBegin(GL_LINE_STRIP);
		/* sample at 1 frame intervals, and draw
		 *	- min y-val is yminc, max is y-maxc, so clamp in those regions
		 */
		for (cfra = strip->start; cfra <= strip->end; cfra += 1.0f) {
			float y = evaluate_fcurve(fcu, cfra);    // assume this to be in 0-1 range
			glVertex2f(cfra, ((y * yheight) + yminc));
		}
		glEnd(); // GL_LINE_STRIP
	}
	else {
		/* use blend in/out values only if both aren't zero */
		if ((IS_EQF(strip->blendin, 0.0f) && IS_EQF(strip->blendout, 0.0f)) == 0) {
			glBegin(GL_LINE_STRIP);
			/* start of strip - if no blendin, start straight at 1, otherwise from 0 to 1 over blendin frames */
			if (IS_EQF(strip->blendin, 0.0f) == 0) {
				glVertex2f(strip->start,                    yminc);
				glVertex2f(strip->start + strip->blendin,   ymaxc);
			}
			else
				glVertex2f(strip->start, ymaxc);
					
			/* end of strip */
			if (IS_EQF(strip->blendout, 0.0f) == 0) {
				glVertex2f(strip->end - strip->blendout,    ymaxc);
				glVertex2f(strip->end,                      yminc);
			}
			else
				glVertex2f(strip->end, ymaxc);
			glEnd(); // GL_LINE_STRIP
		}
	}
	
	/* time -------------------------- */
	// XXX do we want to draw this curve? in a different color too?
	
	/* turn off AA'd lines */
	glDisable(GL_LINE_SMOOTH);
	glDisable(GL_BLEND);
}

/* main call for drawing a single NLA-strip */
static void nla_draw_strip(SpaceNla *snla, AnimData *adt, NlaTrack *nlt, NlaStrip *strip, View2D *v2d, float yminc, float ymaxc)
{
	short nonSolo = ((adt && (adt->flag & ADT_NLA_SOLO_TRACK)) && (nlt->flag & NLATRACK_SOLO) == 0);
	float color[3];
	
	/* get color of strip */
	nla_strip_get_color_inside(adt, strip, color);
	
	/* draw extrapolation info first (as backdrop)
	 *	- but this should only be drawn if track has some contribution
	 */
	if ((strip->extendmode != NLASTRIP_EXTEND_NOTHING) && (nonSolo == 0)) {
		/* enable transparency... */
		glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
		glEnable(GL_BLEND);
		
		switch (strip->extendmode) {
			/* since this does both sides, only do the 'before' side, and leave the rest to the next case */
			case NLASTRIP_EXTEND_HOLD: 
				/* only need to draw here if there's no strip before since 
				 * it only applies in such a situation 
				 */
				if (strip->prev == NULL) {
					/* set the drawing color to the color of the strip, but with very faint alpha */
					glColor4f(color[0], color[1], color[2], 0.15f);
					
					/* draw the rect to the edge of the screen */
					glBegin(GL_QUADS);
					glVertex2f(v2d->cur.xmin, yminc);
					glVertex2f(v2d->cur.xmin, ymaxc);
					glVertex2f(strip->start, ymaxc);
					glVertex2f(strip->start, yminc);
					glEnd();
				}
				/* fall-through */

			/* this only draws after the strip */
			case NLASTRIP_EXTEND_HOLD_FORWARD: 
				/* only need to try and draw if the next strip doesn't occur immediately after */
				if ((strip->next == NULL) || (IS_EQF(strip->next->start, strip->end) == 0)) {
					/* set the drawing color to the color of the strip, but this time less faint */
					glColor4f(color[0], color[1], color[2], 0.3f);
					
					/* draw the rect to the next strip or the edge of the screen */
					glBegin(GL_QUADS);
					glVertex2f(strip->end, yminc);
					glVertex2f(strip->end, ymaxc);
						
					if (strip->next) {
						glVertex2f(strip->next->start, ymaxc);
						glVertex2f(strip->next->start, yminc);
					}
					else {
						glVertex2f(v2d->cur.xmax, ymaxc);
						glVertex2f(v2d->cur.xmax, yminc);
					}
					glEnd();
				}
				break;
		}
		
		glDisable(GL_BLEND);
	}
	
	
	/* draw 'inside' of strip itself */
	if (nonSolo == 0) {
		/* strip is in normal track */
		glColor3fv(color);
		uiSetRoundBox(UI_CNR_ALL); /* all corners rounded */
		
		uiDrawBoxShade(GL_POLYGON, strip->start, yminc, strip->end, ymaxc, 0.0, 0.5, 0.1);
	}
	else {
		/* strip is in disabled track - make less visible */
		glColor4f(color[0], color[1], color[2], 0.1f);
		
		glEnable(GL_BLEND);
		glRectf(strip->start, yminc, strip->end, ymaxc);
		glDisable(GL_BLEND);
	}
	
	
	/* draw strip's control 'curves'
	 *	- only if user hasn't hidden them...
	 */
	if ((snla->flag & SNLA_NOSTRIPCURVES) == 0)
		nla_draw_strip_curves(strip, yminc, ymaxc);
	
	
	/* draw strip outline 
	 *	- color used here is to indicate active vs non-active
	 */
	if (strip->flag & NLASTRIP_FLAG_ACTIVE) {
		/* strip should appear 'sunken', so draw a light border around it */
		glColor3f(0.9f, 1.0f, 0.9f); // FIXME: hardcoded temp-hack colors
	}
	else {
		/* strip should appear to stand out, so draw a dark border around it */
		glColor3f(0.0f, 0.0f, 0.0f);
	}
	
	/* - line style: dotted for muted */
	if (strip->flag & NLASTRIP_FLAG_MUTED)
		setlinestyle(4);
		
	/* draw outline */
	uiDrawBoxShade(GL_LINE_LOOP, strip->start, yminc, strip->end, ymaxc, 0.0, 0.0, 0.1);
	
	/* if action-clip strip, draw lines delimiting repeats too (in the same color as outline) */
	if ((strip->type == NLASTRIP_TYPE_CLIP) && IS_EQF(strip->repeat, 1.0f) == 0) {
		float repeatLen = (strip->actend - strip->actstart) * strip->scale;
		int i;
		
		/* only draw lines for whole-numbered repeats, starting from the first full-repeat
		 * up to the last full repeat (but not if it lies on the end of the strip)
		 */
		for (i = 1; i < strip->repeat; i++) {
			float repeatPos = strip->start + (repeatLen * i);
			
			/* don't draw if line would end up on or after the end of the strip */
			if (repeatPos < strip->end)
				fdrawline(repeatPos, yminc + 4, repeatPos, ymaxc - 4);
		}
	}
	/* or if meta-strip, draw lines delimiting extents of sub-strips (in same color as outline, if more than 1 exists) */
	else if ((strip->type == NLASTRIP_TYPE_META) && (strip->strips.first != strip->strips.last)) {
		NlaStrip *cs;
		float y = (ymaxc - yminc) / 2.0f + yminc;
		
		/* only draw first-level of child-strips, but don't draw any lines on the endpoints */
		for (cs = strip->strips.first; cs; cs = cs->next) {
			/* draw start-line if not same as end of previous (and only if not the first strip) 
			 *	- on upper half of strip
			 */
			if ((cs->prev) && IS_EQF(cs->prev->end, cs->start) == 0)
				fdrawline(cs->start, y, cs->start, ymaxc);
				
			/* draw end-line if not the last strip
			 *	- on lower half of strip
			 */
			if (cs->next) 
				fdrawline(cs->end, yminc, cs->end, y);
		}
	}
	
	/* reset linestyle */
	setlinestyle(0);
} 

/* add the relevant text to the cache of text-strings to draw in pixelspace */
static void nla_draw_strip_text(AnimData *adt, NlaTrack *nlt, NlaStrip *strip, int index, View2D *v2d, float yminc, float ymaxc)
{
	short notSolo = ((adt && (adt->flag & ADT_NLA_SOLO_TRACK)) && (nlt->flag & NLATRACK_SOLO) == 0);
	char str[256];
	size_t str_len;
	char col[4];
	float xofs;
	rctf rect;
	
	/* just print the name and the range */
	if (strip->flag & NLASTRIP_FLAG_TEMP_META) {
		str_len = BLI_snprintf(str, sizeof(str), "%d) Temp-Meta", index);
	}
	else {
		str_len = BLI_strncpy_rlen(str, strip->name, sizeof(str));
	}
	
	/* set text color - if colors (see above) are light, draw black text, otherwise draw white */
	if (strip->flag & (NLASTRIP_FLAG_ACTIVE | NLASTRIP_FLAG_SELECT | NLASTRIP_FLAG_TWEAKUSER)) {
		col[0] = col[1] = col[2] = 0;
	}
	else {
		col[0] = col[1] = col[2] = 255;
	}
	
	/* text opacity depends on whether if there's a solo'd track, this isn't it */
	if (notSolo == 0)
		col[3] = 255;
	else
		col[3] = 128;
	
	/* determine the amount of padding required - cannot be constant otherwise looks weird in some cases */
	if ((strip->end - strip->start) <= 5.0f)
		xofs = 0.5f;
	else
		xofs = 1.0f;
	
	/* set bounding-box for text 
	 *	- padding of 2 'units' on either side
	 */
	// TODO: make this centered?
	rect.xmin = strip->start + xofs;
	rect.ymin = yminc;
	rect.xmax = strip->end - xofs;
	rect.ymax = ymaxc;
	
	/* add this string to the cache of texts to draw */
	UI_view2d_text_cache_add_rectf(v2d, &rect, str, str_len, col);
}

/* add frame extents to cache of text-strings to draw in pixelspace
 * for now, only used when transforming strips
 */
static void nla_draw_strip_frames_text(NlaTrack *UNUSED(nlt), NlaStrip *strip, View2D *v2d, float UNUSED(yminc), float ymaxc)
{
	const float ytol = 1.0f; /* small offset to vertical positioning of text, for legibility */
	const char col[4] = {220, 220, 220, 255}; /* light gray */
	char numstr[32];
	size_t numstr_len;
	
	
	/* Always draw times above the strip, whereas sequencer drew below + above.
	 * However, we should be fine having everything on top, since these tend to be 
	 * quite spaced out. 
	 *	- 1 dp is compromise between lack of precision (ints only, as per sequencer)
	 *	  while also preserving some accuracy, since we do use floats
	 */
	/* start frame */
	numstr_len = BLI_snprintf(numstr, sizeof(numstr), "%.1f", strip->start);
	UI_view2d_text_cache_add(v2d, strip->start - 1.0f, ymaxc + ytol, numstr, numstr_len, col);
	
	/* end frame */
	numstr_len = BLI_snprintf(numstr, sizeof(numstr), "%.1f", strip->end);
	UI_view2d_text_cache_add(v2d, strip->end, ymaxc + ytol, numstr, numstr_len, col);
}

/* ---------------------- */

void draw_nla_main_data(bAnimContext *ac, SpaceNla *snla, ARegion *ar)
{
	ListBase anim_data = {NULL, NULL};
	bAnimListElem *ale;
	int filter;
	
	View2D *v2d = &ar->v2d;
	float y = 0.0f;
	size_t items;
	int height;
	
	/* build list of channels to draw */
	filter = (ANIMFILTER_DATA_VISIBLE | ANIMFILTER_LIST_VISIBLE | ANIMFILTER_LIST_CHANNELS);
	items = ANIM_animdata_filter(ac, &anim_data, filter, ac->data, ac->datatype);
	
	/* Update max-extent of channels here (taking into account scrollers):
	 *  - this is done to allow the channel list to be scrollable, but must be done here
	 *    to avoid regenerating the list again and/or also because channels list is drawn first
	 *	- offset of NLACHANNEL_HEIGHT*2 is added to the height of the channels, as first is for 
	 *	  start of list offset, and the second is as a correction for the scrollers.
	 */
	height = ((items * NLACHANNEL_STEP(snla)) + (NLACHANNEL_HEIGHT(snla) * 2));
	/* don't use totrect set, as the width stays the same 
	 * (NOTE: this is ok here, the configuration is pretty straightforward) 
	 */
	v2d->tot.ymin = (float)(-height);
	
	/* loop through channels, and set up drawing depending on their type  */
	y = (float)(-NLACHANNEL_HEIGHT(snla));
	
	for (ale = anim_data.first; ale; ale = ale->next) {
		const float yminc = (float)(y - NLACHANNEL_HEIGHT_HALF(snla));
		const float ymaxc = (float)(y + NLACHANNEL_HEIGHT_HALF(snla));
		
		/* check if visible */
		if (IN_RANGE(yminc, v2d->cur.ymin, v2d->cur.ymax) ||
		    IN_RANGE(ymaxc, v2d->cur.ymin, v2d->cur.ymax) )
		{
			/* data to draw depends on the type of channel */
			switch (ale->type) {
				case ANIMTYPE_NLATRACK:
				{
					AnimData *adt = ale->adt;
					NlaTrack *nlt = (NlaTrack *)ale->data;
					NlaStrip *strip;
					int index;
					
					/* draw each strip in the track (if visible) */
					for (strip = nlt->strips.first, index = 1; strip; strip = strip->next, index++) {
						if (BKE_nlastrip_within_bounds(strip, v2d->cur.xmin, v2d->cur.xmax)) {
							/* draw the visualization of the strip */
							nla_draw_strip(snla, adt, nlt, strip, v2d, yminc, ymaxc);
							
							/* add the text for this strip to the cache */
							nla_draw_strip_text(adt, nlt, strip, index, v2d, yminc, ymaxc);
							
							/* if transforming strips (only real reason for temp-metas currently), 
							 * add to the cache the frame numbers of the strip's extents
							 */
							if (strip->flag & NLASTRIP_FLAG_TEMP_META)
								nla_draw_strip_frames_text(nlt, strip, v2d, yminc, ymaxc);
						}
					}
					break;
				}
				case ANIMTYPE_NLAACTION:
				{
					AnimData *adt = ale->adt;
					float color[4];
					
					/* just draw a semi-shaded rect spanning the width of the viewable area if there's data,
					 * and a second darker rect within which we draw keyframe indicator dots if there's data
					 */
					glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
					glEnable(GL_BLEND);
						
					/* get colors for drawing */
					nla_action_get_color(adt, ale->data, color);
					glColor4fv(color);
					
					/* draw slightly shifted up for greater separation from standard channels,
					 * but also slightly shorter for some more contrast when viewing the strips
					 */
					glRectf(v2d->cur.xmin, yminc + NLACHANNEL_SKIP, v2d->cur.xmax, ymaxc - NLACHANNEL_SKIP);
					
					/* draw keyframes in the action */
					nla_action_draw_keyframes(adt, ale->data, v2d, y, yminc + NLACHANNEL_SKIP, ymaxc - NLACHANNEL_SKIP);
					
					/* draw 'embossed' lines above and below the strip for effect */
					/* white base-lines */
					glLineWidth(2.0f);
					glColor4f(1.0f, 1.0f, 1.0f, 0.3);
					fdrawline(v2d->cur.xmin, yminc + NLACHANNEL_SKIP, v2d->cur.xmax, yminc + NLACHANNEL_SKIP);
					fdrawline(v2d->cur.xmin, ymaxc - NLACHANNEL_SKIP, v2d->cur.xmax, ymaxc - NLACHANNEL_SKIP);
					
					/* black top-lines */
					glLineWidth(1.0f);
					glColor3f(0.0f, 0.0f, 0.0f);
					fdrawline(v2d->cur.xmin, yminc + NLACHANNEL_SKIP, v2d->cur.xmax, yminc + NLACHANNEL_SKIP);
					fdrawline(v2d->cur.xmin, ymaxc - NLACHANNEL_SKIP, v2d->cur.xmax, ymaxc - NLACHANNEL_SKIP);
					
					glDisable(GL_BLEND);
					break;
				}
			}
		}
		
		/* adjust y-position for next one */
		y -= NLACHANNEL_STEP(snla);
	}
	
	/* free tempolary channels */
	ANIM_animdata_freelist(&anim_data);
}

/* *********************************************** */
/* Channel List */

void draw_nla_channel_list(bContext *C, bAnimContext *ac, ARegion *ar)
{
	ListBase anim_data = {NULL, NULL};
	bAnimListElem *ale;
	int filter;
	
	SpaceNla *snla = (SpaceNla *)ac->sl;
	View2D *v2d = &ar->v2d;
	float y = 0.0f;
	size_t items;
	int height;
	
	/* build list of channels to draw */
	filter = (ANIMFILTER_DATA_VISIBLE | ANIMFILTER_LIST_VISIBLE | ANIMFILTER_LIST_CHANNELS);
	items = ANIM_animdata_filter(ac, &anim_data, filter, ac->data, ac->datatype);
	
	/* Update max-extent of channels here (taking into account scrollers):
	 *  - this is done to allow the channel list to be scrollable, but must be done here
	 *    to avoid regenerating the list again and/or also because channels list is drawn first
	 *	- offset of NLACHANNEL_HEIGHT*2 is added to the height of the channels, as first is for 
	 *	  start of list offset, and the second is as a correction for the scrollers.
	 */
	height = ((items * NLACHANNEL_STEP(snla)) + (NLACHANNEL_HEIGHT(snla) * 2));
	/* don't use totrect set, as the width stays the same 
	 * (NOTE: this is ok here, the configuration is pretty straightforward) 
	 */
	v2d->tot.ymin = (float)(-height);
	/* need to do a view-sync here, so that the keys area doesn't jump around (it must copy this) */
	UI_view2d_sync(NULL, ac->sa, v2d, V2D_LOCK_COPY);
	
	/* draw channels */
	{   /* first pass: just the standard GL-drawing for backdrop + text */
		y = (float)(-NLACHANNEL_HEIGHT(snla));
		
		for (ale = anim_data.first; ale; ale = ale->next) {
			float yminc = (float)(y -  NLACHANNEL_HEIGHT_HALF(snla));
			float ymaxc = (float)(y +  NLACHANNEL_HEIGHT_HALF(snla));
			
			/* check if visible */
			if (IN_RANGE(yminc, v2d->cur.ymin, v2d->cur.ymax) ||
			    IN_RANGE(ymaxc, v2d->cur.ymin, v2d->cur.ymax) )
			{
				/* draw all channels using standard channel-drawing API */
				ANIM_channel_draw(ac, ale, yminc, ymaxc);
			}
			
			/* adjust y-position for next one */
			y -= NLACHANNEL_STEP(snla);
		}
	}
	{   /* second pass: UI widgets */
		uiBlock *block = uiBeginBlock(C, ar, __func__, UI_EMBOSS);
		size_t channel_index = 0;
		
		y = (float)(-NLACHANNEL_HEIGHT(snla));
		
		/* set blending again, as may not be set in previous step */
		glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
		glEnable(GL_BLEND);
		
		/* loop through channels, and set up drawing depending on their type  */
		for (ale = anim_data.first; ale; ale = ale->next) {
			const float yminc = (float)(y - NLACHANNEL_HEIGHT_HALF(snla));
			const float ymaxc = (float)(y + NLACHANNEL_HEIGHT_HALF(snla));
			
			/* check if visible */
			if (IN_RANGE(yminc, v2d->cur.ymin, v2d->cur.ymax) ||
			    IN_RANGE(ymaxc, v2d->cur.ymin, v2d->cur.ymax) )
			{
				/* draw all channels using standard channel-drawing API */
				ANIM_channel_draw_widgets(C, ac, ale, block, yminc, ymaxc, channel_index);
			}
			
			/* adjust y-position for next one */
			y -= NLACHANNEL_STEP(snla);
			channel_index++;
		}
		
		uiEndBlock(C, block);
		uiDrawBlock(C, block);
		
		glDisable(GL_BLEND);
	}
	
	/* free temporary channels */
	ANIM_animdata_freelist(&anim_data);
}

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