/*
 * ***** 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) Blender Foundation
 *
 * Contributor(s): Joshua Leung (2009 Recode)
 *
 * ***** END GPL LICENSE BLOCK *****
 */

/** \file blender/editors/space_graph/graph_draw.c
 *  \ingroup spgraph
 */


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

#include "BLI_blenlib.h"
#include "BLI_math.h"
#include "BLI_utildefines.h"

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

#include "BKE_context.h"
#include "BKE_curve.h"
#include "BKE_fcurve.h"

#include "BIF_glutil.h"

#include "GPU_draw.h"
#include "GPU_immediate.h"
#include "GPU_matrix.h"
#include "GPU_state.h"

#include "ED_anim_api.h"

#include "graph_intern.h"

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

/* *************************** */
/* Utility Drawing Defines */

/* determine the alpha value that should be used when
 * drawing components for some F-Curve (fcu)
 *	- selected F-Curves should be more visible than partially visible ones
 */
static float fcurve_display_alpha(FCurve *fcu)
{
	return (fcu->flag & FCURVE_SELECTED) ? 1.0f : U.fcu_inactive_alpha;
}

/* *************************** */
/* F-Curve Modifier Drawing */

/* Envelope -------------- */

/* TODO: draw a shaded poly showing the region of influence too!!! */
static void draw_fcurve_modifier_controls_envelope(FModifier *fcm, View2D *v2d)
{
	FMod_Envelope *env = (FMod_Envelope *)fcm->data;
	FCM_EnvelopeData *fed;
	const float fac = 0.05f * BLI_rctf_size_x(&v2d->cur);
	int i;

	const uint shdr_pos = GWN_vertformat_attr_add(immVertexFormat(), "pos", GWN_COMP_F32, 2, GWN_FETCH_FLOAT);

	GPU_line_width(1.0f);

	immBindBuiltinProgram(GPU_SHADER_2D_LINE_DASHED_UNIFORM_COLOR);

	float viewport_size[4];
	GPU_viewport_size_get_f(viewport_size);
	immUniform2f("viewport_size", viewport_size[2] / UI_DPI_FAC, viewport_size[3] / UI_DPI_FAC);

	immUniform1i("colors_len", 0);  /* Simple dashes. */
	immUniformColor3f(0.0f, 0.0f, 0.0f);
	immUniform1f("dash_width", 10.0f);
	immUniform1f("dash_factor", 0.5f);

	/* draw two black lines showing the standard reference levels */

	immBegin(GWN_PRIM_LINES, 4);
	immVertex2f(shdr_pos, v2d->cur.xmin, env->midval + env->min);
	immVertex2f(shdr_pos, v2d->cur.xmax, env->midval + env->min);

	immVertex2f(shdr_pos, v2d->cur.xmin, env->midval + env->max);
	immVertex2f(shdr_pos, v2d->cur.xmax, env->midval + env->max);
	immEnd();

	immUnbindProgram();

	if (env->totvert > 0) {
		/* set size of vertices (non-adjustable for now) */
		GPU_point_size(2.0f);

		immBindBuiltinProgram(GPU_SHADER_2D_UNIFORM_COLOR);

		/* for now, point color is fixed, and is white */
		immUniformColor3f(1.0f, 1.0f, 1.0f);

		immBeginAtMost(GWN_PRIM_POINTS, env->totvert * 2);

		for (i = 0, fed = env->data; i < env->totvert; i++, fed++) {
			/* only draw if visible
			 *	- min/max here are fixed, not relative
			 */
			if (IN_RANGE(fed->time, (v2d->cur.xmin - fac), (v2d->cur.xmax + fac))) {
				immVertex2f(shdr_pos, fed->time, fed->min);
				immVertex2f(shdr_pos, fed->time, fed->max);
			}
		}

		immEnd();

		immUnbindProgram();
	}
}

/* *************************** */
/* F-Curve Drawing */

/* Points ---------------- */

/* helper func - set color to draw F-Curve data with */
static void set_fcurve_vertex_color(FCurve *fcu, bool sel)
{
	float color[4];
	float diff;

	/* Set color of curve vertex based on state of curve (i.e. 'Edit' Mode) */
	if ((fcu->flag & FCURVE_PROTECTED) == 0) {
		/* Curve's points ARE BEING edited */
		UI_GetThemeColor3fv(sel ? TH_VERTEX_SELECT : TH_VERTEX, color);
	}
	else {
		/* Curve's points CANNOT BE edited */
		UI_GetThemeColor3fv(sel ? TH_TEXT_HI : TH_TEXT, color);
	}

	/* Fade the 'intensity' of the vertices based on the selection of the curves too
	 * - Only fade by 50% the amount the curves were faded by, so that the points
	 *   still stand out for easier selection
	 */
	diff = 1.0f - fcurve_display_alpha(fcu);
	color[3] = 1.0f - (diff * 0.5f);
	CLAMP(color[3], 0.2f, 1.0f);

	immUniformColor4fv(color);
}

static void draw_fcurve_selected_keyframe_vertices(FCurve *fcu, View2D *v2d, bool edit, bool sel, unsigned pos)
{
	const float fac = 0.05f * BLI_rctf_size_x(&v2d->cur);

	set_fcurve_vertex_color(fcu, sel);

	immBeginAtMost(GWN_PRIM_POINTS, fcu->totvert);

	BezTriple *bezt = fcu->bezt;
	for (int i = 0; i < fcu->totvert; i++, bezt++) {
		/* as an optimization step, only draw those in view
		 *	- we apply a correction factor to ensure that points don't pop in/out due to slight twitches of view size
		 */
		if (IN_RANGE(bezt->vec[1][0], (v2d->cur.xmin - fac), (v2d->cur.xmax + fac))) {
			if (edit) {
				/* 'Keyframe' vertex only, as handle lines and handles have already been drawn
				 *	- only draw those with correct selection state for the current drawing color
				 *	-
				 */
				if ((bezt->f2 & SELECT) == sel)
					immVertex2fv(pos, bezt->vec[1]);
			}
			else {
				/* no check for selection here, as curve is not editable... */
				/* XXX perhaps we don't want to even draw points?   maybe add an option for that later */
				immVertex2fv(pos, bezt->vec[1]);
			}
		}
	}

	immEnd();
}

/* helper func - draw keyframe vertices only for an F-Curve */
static void draw_fcurve_keyframe_vertices(FCurve *fcu, View2D *v2d, bool edit, unsigned pos)
{
	immBindBuiltinProgram(GPU_SHADER_2D_POINT_UNIFORM_SIZE_UNIFORM_COLOR_AA);

	immUniform1f("size", UI_GetThemeValuef(TH_VERTEX_SIZE) * U.pixelsize);

	draw_fcurve_selected_keyframe_vertices(fcu, v2d, edit, false, pos);
	draw_fcurve_selected_keyframe_vertices(fcu, v2d, edit, true, pos);

	immUnbindProgram();
}


/* helper func - draw handle vertices only for an F-Curve (if it is not protected) */
static void draw_fcurve_selected_handle_vertices(FCurve *fcu, View2D *v2d, bool sel, bool sel_handle_only, unsigned pos)
{
	(void) v2d; /* TODO: use this to draw only points in view */

	/* set handle color */
	float hcolor[3];
	UI_GetThemeColor3fv(sel ? TH_HANDLE_VERTEX_SELECT : TH_HANDLE_VERTEX, hcolor);
	immUniform4f("outlineColor", hcolor[0], hcolor[1], hcolor[2], 1.0f);
	immUniformColor3fvAlpha(hcolor, 0.01f); /* almost invisible - only keep for smoothness */

	immBeginAtMost(GWN_PRIM_POINTS, fcu->totvert * 2);

	BezTriple *bezt = fcu->bezt;
	BezTriple *prevbezt = NULL;
	for (int i = 0; i < fcu->totvert; i++, prevbezt = bezt, bezt++) {
		/* Draw the editmode handles for a bezier curve (others don't have handles)
		 * if their selection status matches the selection status we're drawing for
		 *	- first handle only if previous beztriple was bezier-mode
		 *	- second handle only if current beztriple is bezier-mode
		 *
		 * Also, need to take into account whether the keyframe was selected
		 * if a Graph Editor option to only show handles of selected keys is on.
		 */
		if (!sel_handle_only || BEZT_ISSEL_ANY(bezt)) {
			if ((!prevbezt && (bezt->ipo == BEZT_IPO_BEZ)) || (prevbezt && (prevbezt->ipo == BEZT_IPO_BEZ))) {
				if ((bezt->f1 & SELECT) == sel) /* && v2d->cur.xmin < bezt->vec[0][0] < v2d->cur.xmax)*/
					immVertex2fv(pos, bezt->vec[0]);
			}

			if (bezt->ipo == BEZT_IPO_BEZ) {
				if ((bezt->f3 & SELECT) == sel) /* && v2d->cur.xmin < bezt->vec[2][0] < v2d->cur.xmax)*/
					immVertex2fv(pos, bezt->vec[2]);
			}
		}
	}

	immEnd();
}

/* helper func - draw handle vertices only for an F-Curve (if it is not protected) */
static void draw_fcurve_handle_vertices(FCurve *fcu, View2D *v2d, bool sel_handle_only, unsigned pos)
{
	/* smooth outlines for more consistent appearance */
	immBindBuiltinProgram(GPU_SHADER_2D_POINT_UNIFORM_SIZE_UNIFORM_COLOR_OUTLINE_AA);

	/* set handle size */
	immUniform1f("size", (1.4f * UI_GetThemeValuef(TH_HANDLE_VERTEX_SIZE)) * U.pixelsize);
	immUniform1f("outlineWidth", 1.5f * U.pixelsize);

	draw_fcurve_selected_handle_vertices(fcu, v2d, false, sel_handle_only, pos);
	draw_fcurve_selected_handle_vertices(fcu, v2d, true, sel_handle_only, pos);

	immUnbindProgram();
}


static void draw_fcurve_vertices(ARegion *ar, FCurve *fcu, bool do_handles, bool sel_handle_only)
{
	View2D *v2d = &ar->v2d;

	/* only draw points if curve is visible
	 *  - draw unselected points before selected points as separate passes
	 *     to make sure in the case of overlapping points that the selected is always visible
	 *	- draw handles before keyframes, so that keyframes will overlap handles (keyframes are more important for users)
	 */

	uint pos = GWN_vertformat_attr_add(immVertexFormat(), "pos", GWN_COMP_F32, 2, GWN_FETCH_FLOAT);

	GPU_blend(true);
	GPU_enable_program_point_size();

	/* draw the two handles first (if they're shown, the curve doesn't have just a single keyframe, and the curve is being edited) */
	if (do_handles) {
		draw_fcurve_handle_vertices(fcu, v2d, sel_handle_only, pos);
	}

	/* draw keyframes over the handles */
	draw_fcurve_keyframe_vertices(fcu, v2d, !(fcu->flag & FCURVE_PROTECTED), pos);

	GPU_disable_program_point_size();
	GPU_blend(false);
}

/* Handles ---------------- */

static bool draw_fcurve_handles_check(SpaceIpo *sipo, FCurve *fcu)
{
	/* don't draw handle lines if handles are not to be shown */
	if (    (sipo->flag & SIPO_NOHANDLES) || /* handles shouldn't be shown anywhere */
	        (fcu->flag & FCURVE_PROTECTED) || /* keyframes aren't editable */
#if 0       /* handles can still be selected and handle types set, better draw - campbell */
	        (fcu->flag & FCURVE_INT_VALUES) || /* editing the handles here will cause weird/incorrect interpolation issues */
#endif
	        ((fcu->grp) && (fcu->grp->flag & AGRP_PROTECTED)) || /* group that curve belongs to is not editable */
	        (fcu->totvert <= 1) /* do not show handles if there is only 1 keyframe, otherwise they all clump together in an ugly ball */
	        )
	{
		return false;
	}
	else {
		return true;
	}
}

/* draw lines for F-Curve handles only (this is only done in EditMode)
 * note: draw_fcurve_handles_check must be checked before running this. */
static void draw_fcurve_handles(SpaceIpo *sipo, FCurve *fcu)
{
	int sel, b;

	Gwn_VertFormat *format = immVertexFormat();
	uint pos = GWN_vertformat_attr_add(format, "pos", GWN_COMP_F32, 2, GWN_FETCH_FLOAT);
	uint color = GWN_vertformat_attr_add(format, "color", GWN_COMP_U8, 4, GWN_FETCH_INT_TO_FLOAT_UNIT);
	immBindBuiltinProgram(GPU_SHADER_2D_FLAT_COLOR);

	immBeginAtMost(GWN_PRIM_LINES, 4 * 2 * fcu->totvert);

	/* slightly hacky, but we want to draw unselected points before selected ones
	 * so that selected points are clearly visible
	 */
	for (sel = 0; sel < 2; sel++) {
		BezTriple *bezt = fcu->bezt, *prevbezt = NULL;
		int basecol = (sel) ? TH_HANDLE_SEL_FREE : TH_HANDLE_FREE;
		const float *fp;
		unsigned char col[4];

		for (b = 0; b < fcu->totvert; b++, prevbezt = bezt, bezt++) {
			/* if only selected keyframes can get their handles shown,
			 * check that keyframe is selected
			 */
			if (sipo->flag & SIPO_SELVHANDLESONLY) {
				if (BEZT_ISSEL_ANY(bezt) == 0)
					continue;
			}

			/* draw handle with appropriate set of colors if selection is ok */
			if ((bezt->f2 & SELECT) == sel) {
				fp = bezt->vec[0];

				/* only draw first handle if previous segment had handles */
				if ((!prevbezt && (bezt->ipo == BEZT_IPO_BEZ)) || (prevbezt && (prevbezt->ipo == BEZT_IPO_BEZ))) {
					UI_GetThemeColor3ubv(basecol + bezt->h1, col);
					col[3] = fcurve_display_alpha(fcu) * 255;
					immAttrib4ubv(color, col);
					immVertex2fv(pos, fp);
					immAttrib4ubv(color, col);
					immVertex2fv(pos, fp + 3);
				}

				/* only draw second handle if this segment is bezier */
				if (bezt->ipo == BEZT_IPO_BEZ) {
					UI_GetThemeColor3ubv(basecol + bezt->h2, col);
					col[3] = fcurve_display_alpha(fcu) * 255;
					immAttrib4ubv(color, col);
					immVertex2fv(pos, fp + 3);
					immAttrib4ubv(color, col);
					immVertex2fv(pos, fp + 6);
				}
			}
			else {
				/* only draw first handle if previous segment was had handles, and selection is ok */
				if (((bezt->f1 & SELECT) == sel) &&
				    ((!prevbezt && (bezt->ipo == BEZT_IPO_BEZ)) || (prevbezt && (prevbezt->ipo == BEZT_IPO_BEZ))))
				{
					fp = bezt->vec[0];
					UI_GetThemeColor3ubv(basecol + bezt->h1, col);
					col[3] = fcurve_display_alpha(fcu) * 255;
					immAttrib4ubv(color, col);
					immVertex2fv(pos, fp);
					immAttrib4ubv(color, col);
					immVertex2fv(pos, fp + 3);
				}

				/* only draw second handle if this segment is bezier, and selection is ok */
				if (((bezt->f3 & SELECT) == sel) &&
				    (bezt->ipo == BEZT_IPO_BEZ))
				{
					fp = bezt->vec[1];
					UI_GetThemeColor3ubv(basecol + bezt->h2, col);
					col[3] = fcurve_display_alpha(fcu) * 255;
					immAttrib4ubv(color, col);
					immVertex2fv(pos, fp);
					immAttrib4ubv(color, col);
					immVertex2fv(pos, fp + 3);
				}
			}
		}
	}

	immEnd();
	immUnbindProgram();
}

/* Samples ---------------- */

/* helper func - draw sample-range marker for an F-Curve as a cross
 * NOTE: the caller MUST HAVE GL_LINE_SMOOTH & GL_BLEND ENABLED, otherwise, the controls don't
 * have a consistent appearance (due to off-pixel alignments)...
 */
static void draw_fcurve_sample_control(float x, float y, float xscale, float yscale, float hsize, unsigned int pos)
{
	/* adjust view transform before starting */
	gpuPushMatrix();
	gpuTranslate2f(x, y);
	gpuScale2f(1.0f / xscale * hsize, 1.0f / yscale * hsize);

	/* draw X shape */
	immBegin(GWN_PRIM_LINES, 4);
	immVertex2f(pos, -0.7f, -0.7f);
	immVertex2f(pos, +0.7f, +0.7f);

	immVertex2f(pos, -0.7f, +0.7f);
	immVertex2f(pos, +0.7f, -0.7f);
	immEnd();

	/* restore view transform */
	gpuPopMatrix();
}

/* helper func - draw keyframe vertices only for an F-Curve */
static void draw_fcurve_samples(SpaceIpo *sipo, ARegion *ar, FCurve *fcu)
{
	FPoint *first, *last;
	float hsize, xscale, yscale;

	/* get view settings */
	hsize = UI_GetThemeValuef(TH_VERTEX_SIZE);
	UI_view2d_scale_get(&ar->v2d, &xscale, &yscale);

	/* get verts */
	first = fcu->fpt;
	last = (first) ? (first + (fcu->totvert - 1)) : (NULL);

	/* draw */
	if (first && last) {
		/* anti-aliased lines for more consistent appearance */
		if ((sipo->flag & SIPO_BEAUTYDRAW_OFF) == 0) GPU_line_smooth(true);
		GPU_blend(true);

		uint pos = GWN_vertformat_attr_add(immVertexFormat(), "pos", GWN_COMP_F32, 2, GWN_FETCH_FLOAT);
		immBindBuiltinProgram(GPU_SHADER_2D_UNIFORM_COLOR);

		immUniformThemeColor((fcu->flag & FCURVE_SELECTED) ? TH_TEXT_HI : TH_TEXT);

		draw_fcurve_sample_control(first->vec[0], first->vec[1], xscale, yscale, hsize, pos);
		draw_fcurve_sample_control(last->vec[0], last->vec[1], xscale, yscale, hsize, pos);

		immUnbindProgram();

		GPU_blend(false);
		if ((sipo->flag & SIPO_BEAUTYDRAW_OFF) == 0) GPU_line_smooth(false);
	}
}

/* Curve ---------------- */

/* helper func - just draw the F-Curve by sampling the visible region (for drawing curves with modifiers) */
static void draw_fcurve_curve(bAnimContext *ac, ID *id, FCurve *fcu, View2D *v2d, View2DGrid *grid, unsigned int pos)
{
	SpaceIpo *sipo = (SpaceIpo *)ac->sl;
	ChannelDriver *driver;
	float samplefreq;
	float stime, etime;
	float unitFac, offset;
	float dx, dy;
	short mapping_flag = ANIM_get_normalization_flags(ac);
	int i, n;

	/* when opening a blend file on a different sized screen or while dragging the toolbar this can happen
	 * best just bail out in this case */
	UI_view2d_grid_size(grid, &dx, &dy);
	if (dx <= 0.0f)
		return;


	/* disable any drivers temporarily */
	driver = fcu->driver;
	fcu->driver = NULL;

	/* compute unit correction factor */
	unitFac = ANIM_unit_mapping_get_factor(ac->scene, id, fcu, mapping_flag, &offset);

	/* Note about sampling frequency:
	 *  Ideally, this is chosen such that we have 1-2 pixels = 1 segment
	 *	which means that our curves can be as smooth as possible. However,
	 *  this does mean that curves may not be fully accurate (i.e. if they have
	 *  sudden spikes which happen at the sampling point, we may have problems).
	 *  Also, this may introduce lower performance on less densely detailed curves,
	 *	though it is impossible to predict this from the modifiers!
	 *
	 *	If the automatically determined sampling frequency is likely to cause an infinite
	 *	loop (i.e. too close to 0), then clamp it to a determined "safe" value. The value
	 *  chosen here is just the coarsest value which still looks reasonable...
	 */
	/* grid->dx represents the number of 'frames' between gridlines, but we divide by U.v2d_min_gridsize to get pixels-steps */
	/* TODO: perhaps we should have 1.0 frames as upper limit so that curves don't get too distorted? */
	samplefreq = dx / (U.v2d_min_gridsize * U.pixelsize);

	if (sipo->flag & SIPO_BEAUTYDRAW_OFF) {
		/* Low Precision = coarse lower-bound clamping
		 *
		 * Although the "Beauty Draw" flag was originally for AA'd
		 * line drawing, the sampling rate here has a much greater
		 * impact on performance (e.g. for T40372)!
		 *
		 * This one still amounts to 10 sample-frames for each 1-frame interval
		 * which should be quite a decent approximation in many situations.
		 */
		if (samplefreq < 0.1f)
			samplefreq = 0.1f;
	}
	else {
		/* "Higher Precision" but slower - especially on larger windows (e.g. T40372) */
		if (samplefreq < 0.00001f)
			samplefreq = 0.00001f;
	}


	/* the start/end times are simply the horizontal extents of the 'cur' rect */
	stime = v2d->cur.xmin;
	etime = v2d->cur.xmax + samplefreq; /* + samplefreq here so that last item gets included... */


	/* at each sampling interval, add a new vertex
	 *	- apply the unit correction factor to the calculated values so that
	 *	  the displayed values appear correctly in the viewport
	 */

	n = (etime - stime) / samplefreq + 0.5f;

	if (n > 0) {
		immBegin(GWN_PRIM_LINE_STRIP, (n + 1));

		for (i = 0; i <= n; i++) {
			float ctime = stime + i * samplefreq;
			immVertex2f(pos, ctime, (evaluate_fcurve(fcu, ctime) + offset) * unitFac);
		}

		immEnd();
	}

	/* restore driver */
	fcu->driver = driver;
}

/* helper func - draw a samples-based F-Curve */
static void draw_fcurve_curve_samples(bAnimContext *ac, ID *id, FCurve *fcu, View2D *v2d, const uint shdr_pos)
{
	FPoint *prevfpt = fcu->fpt;
	FPoint *fpt = prevfpt + 1;
	float fac, v[2];
	int b = fcu->totvert;
	float unit_scale, offset;
	short mapping_flag = ANIM_get_normalization_flags(ac);
	int count = fcu->totvert;

	if (prevfpt->vec[0] > v2d->cur.xmin) {
		count++;
	}

	if ((prevfpt + b - 1)->vec[0] < v2d->cur.xmax) {
		count++;
	}

	/* apply unit mapping */
	gpuPushMatrix();
	unit_scale = ANIM_unit_mapping_get_factor(ac->scene, id, fcu, mapping_flag, &offset);
	gpuScale2f(1.0f, unit_scale);
	gpuTranslate2f(0.0f, offset);

	immBegin(GWN_PRIM_LINE_STRIP, count);

	/* extrapolate to left? - left-side of view comes before first keyframe? */
	if (prevfpt->vec[0] > v2d->cur.xmin) {
		v[0] = v2d->cur.xmin;

		/* y-value depends on the interpolation */
		if ((fcu->extend == FCURVE_EXTRAPOLATE_CONSTANT) || (fcu->flag & FCURVE_INT_VALUES) || (fcu->totvert == 1)) {
			/* just extend across the first keyframe's value */
			v[1] = prevfpt->vec[1];
		}
		else {
			/* extrapolate linear doesn't use the handle, use the next points center instead */
			fac = (prevfpt->vec[0] - fpt->vec[0]) / (prevfpt->vec[0] - v[0]);
			if (fac) fac = 1.0f / fac;
			v[1] = prevfpt->vec[1] - fac * (prevfpt->vec[1] - fpt->vec[1]);
		}

		immVertex2fv(shdr_pos, v);
	}

	/* loop over samples, drawing segments */
	/* draw curve between first and last keyframe (if there are enough to do so) */
	while (b--) {
		/* Linear interpolation: just add one point (which should add a new line segment) */
		immVertex2fv(shdr_pos, prevfpt->vec);

		/* get next pointers */
		if (b > 0) {
			prevfpt++;
		}
	}

	/* extrapolate to right? (see code for left-extrapolation above too) */
	if (prevfpt->vec[0] < v2d->cur.xmax) {
		v[0] = v2d->cur.xmax;

		/* y-value depends on the interpolation */
		if ((fcu->extend == FCURVE_EXTRAPOLATE_CONSTANT) || (fcu->flag & FCURVE_INT_VALUES) || (fcu->totvert == 1)) {
			/* based on last keyframe's value */
			v[1] = prevfpt->vec[1];
		}
		else {
			/* extrapolate linear doesn't use the handle, use the previous points center instead */
			fpt = prevfpt - 1;
			fac = (prevfpt->vec[0] - fpt->vec[0]) / (prevfpt->vec[0] - v[0]);
			if (fac) fac = 1.0f / fac;
			v[1] = prevfpt->vec[1] - fac * (prevfpt->vec[1] - fpt->vec[1]);
		}

		immVertex2fv(shdr_pos, v);
	}

	immEnd();

	gpuPopMatrix();
}

/* helper func - check if the F-Curve only contains easily drawable segments
 * (i.e. no easing equation interpolations)
 */
static bool fcurve_can_use_simple_bezt_drawing(FCurve *fcu)
{
	BezTriple *bezt;
	int i;

	for (i = 0, bezt = fcu->bezt; i < fcu->totvert; i++, bezt++) {
		if (ELEM(bezt->ipo, BEZT_IPO_CONST, BEZT_IPO_LIN, BEZT_IPO_BEZ) == false) {
			return false;
		}
	}

	return true;
}

/* helper func - draw one repeat of an F-Curve (using Bezier curve approximations) */
static void draw_fcurve_curve_bezts(bAnimContext *ac, ID *id, FCurve *fcu, View2D *v2d, unsigned int pos)
{
	BezTriple *prevbezt = fcu->bezt;
	BezTriple *bezt = prevbezt + 1;
	float v1[2], v2[2], v3[2], v4[2];
	float *fp, data[120];
	float fac = 0.0f;
	int b = fcu->totvert - 1;
	int resol;
	float unit_scale, offset;
	short mapping_flag = ANIM_get_normalization_flags(ac);

	/* apply unit mapping */
	gpuPushMatrix();
	unit_scale = ANIM_unit_mapping_get_factor(ac->scene, id, fcu, mapping_flag, &offset);
	gpuScale2f(1.0f, unit_scale);
	gpuTranslate2f(0.0f, offset);

	/* For now, this assumes the worst case scenario, where all the keyframes have
	 * bezier interpolation, and are drawn at full res.
	 * This is tricky to optimize, but maybe can be improved at some point... */
	immBeginAtMost(GWN_PRIM_LINE_STRIP, (b * 32 + 3));

	/* extrapolate to left? */
	if (prevbezt->vec[1][0] > v2d->cur.xmin) {
		/* left-side of view comes before first keyframe, so need to extend as not cyclic */
		v1[0] = v2d->cur.xmin;

		/* y-value depends on the interpolation */
		if ((fcu->extend == FCURVE_EXTRAPOLATE_CONSTANT) || (prevbezt->ipo == BEZT_IPO_CONST) || (fcu->totvert == 1)) {
			/* just extend across the first keyframe's value */
			v1[1] = prevbezt->vec[1][1];
		}
		else if (prevbezt->ipo == BEZT_IPO_LIN) {
			/* extrapolate linear dosnt use the handle, use the next points center instead */
			fac = (prevbezt->vec[1][0] - bezt->vec[1][0]) / (prevbezt->vec[1][0] - v1[0]);
			if (fac) fac = 1.0f / fac;
			v1[1] = prevbezt->vec[1][1] - fac * (prevbezt->vec[1][1] - bezt->vec[1][1]);
		}
		else {
			/* based on angle of handle 1 (relative to keyframe) */
			fac = (prevbezt->vec[0][0] - prevbezt->vec[1][0]) / (prevbezt->vec[1][0] - v1[0]);
			if (fac) fac = 1.0f / fac;
			v1[1] = prevbezt->vec[1][1] - fac * (prevbezt->vec[0][1] - prevbezt->vec[1][1]);
		}

		immVertex2fv(pos, v1);
	}

	/* if only one keyframe, add it now */
	if (fcu->totvert == 1) {
		v1[0] = prevbezt->vec[1][0];
		v1[1] = prevbezt->vec[1][1];
		immVertex2fv(pos, v1);
	}

	/* draw curve between first and last keyframe (if there are enough to do so) */
	/* TODO: optimize this to not have to calc stuff out of view too? */
	while (b--) {
		if (prevbezt->ipo == BEZT_IPO_CONST) {
			/* Constant-Interpolation: draw segment between previous keyframe and next, but holding same value */
			v1[0] = prevbezt->vec[1][0];
			v1[1] = prevbezt->vec[1][1];
			immVertex2fv(pos, v1);

			v1[0] = bezt->vec[1][0];
			v1[1] = prevbezt->vec[1][1];
			immVertex2fv(pos, v1);
		}
		else if (prevbezt->ipo == BEZT_IPO_LIN) {
			/* Linear interpolation: just add one point (which should add a new line segment) */
			v1[0] = prevbezt->vec[1][0];
			v1[1] = prevbezt->vec[1][1];
			immVertex2fv(pos, v1);
		}
		else if (prevbezt->ipo == BEZT_IPO_BEZ) {
			/* Bezier-Interpolation: draw curve as series of segments between keyframes
			 *	- resol determines number of points to sample in between keyframes
			 */

			/* resol depends on distance between points (not just horizontal) OR is a fixed high res */
			/* TODO: view scale should factor into this someday too... */
			if (fcu->driver) {
				resol = 32;
			}
			else {
				resol = (int)(5.0f * len_v2v2(bezt->vec[1], prevbezt->vec[1]));
			}

			if (resol < 2) {
				/* only draw one */
				v1[0] = prevbezt->vec[1][0];
				v1[1] = prevbezt->vec[1][1];
				immVertex2fv(pos, v1);
			}
			else {
				/* clamp resolution to max of 32 */
				/* NOTE: higher values will crash */
				if (resol > 32) resol = 32;

				v1[0] = prevbezt->vec[1][0];
				v1[1] = prevbezt->vec[1][1];
				v2[0] = prevbezt->vec[2][0];
				v2[1] = prevbezt->vec[2][1];

				v3[0] = bezt->vec[0][0];
				v3[1] = bezt->vec[0][1];
				v4[0] = bezt->vec[1][0];
				v4[1] = bezt->vec[1][1];

				correct_bezpart(v1, v2, v3, v4);

				BKE_curve_forward_diff_bezier(v1[0], v2[0], v3[0], v4[0], data, resol, sizeof(float) * 3);
				BKE_curve_forward_diff_bezier(v1[1], v2[1], v3[1], v4[1], data + 1, resol, sizeof(float) * 3);

				for (fp = data; resol; resol--, fp += 3) {
					immVertex2fv(pos, fp);
				}
			}
		}

		/* get next pointers */
		prevbezt = bezt;
		bezt++;

		/* last point? */
		if (b == 0) {
			v1[0] = prevbezt->vec[1][0];
			v1[1] = prevbezt->vec[1][1];
			immVertex2fv(pos, v1);
		}
	}

	/* extrapolate to right? (see code for left-extrapolation above too) */
	if (prevbezt->vec[1][0] < v2d->cur.xmax) {
		v1[0] = v2d->cur.xmax;

		/* y-value depends on the interpolation */
		if ((fcu->extend == FCURVE_EXTRAPOLATE_CONSTANT) || (fcu->flag & FCURVE_INT_VALUES) || (prevbezt->ipo == BEZT_IPO_CONST) || (fcu->totvert == 1)) {
			/* based on last keyframe's value */
			v1[1] = prevbezt->vec[1][1];
		}
		else if (prevbezt->ipo == BEZT_IPO_LIN) {
			/* extrapolate linear dosnt use the handle, use the previous points center instead */
			bezt = prevbezt - 1;
			fac = (prevbezt->vec[1][0] - bezt->vec[1][0]) / (prevbezt->vec[1][0] - v1[0]);
			if (fac) fac = 1.0f / fac;
			v1[1] = prevbezt->vec[1][1] - fac * (prevbezt->vec[1][1] - bezt->vec[1][1]);
		}
		else {
			/* based on angle of handle 1 (relative to keyframe) */
			fac = (prevbezt->vec[2][0] - prevbezt->vec[1][0]) / (prevbezt->vec[1][0] - v1[0]);
			if (fac) fac = 1.0f / fac;
			v1[1] = prevbezt->vec[1][1] - fac * (prevbezt->vec[2][1] - prevbezt->vec[1][1]);
		}

		immVertex2fv(pos, v1);
	}

	immEnd();

	gpuPopMatrix();
}

/* Debugging -------------------------------- */

/* Draw indicators which show the value calculated from the driver,
 * and how this is mapped to the value that comes out of it. This
 * is handy for helping users better understand how to interpret
 * the graphs, and also facilitates debugging.
 */
static void graph_draw_driver_debug(bAnimContext *ac, ID *id, FCurve *fcu)
{
	ChannelDriver *driver = fcu->driver;
	View2D *v2d = &ac->ar->v2d;
	short mapping_flag = ANIM_get_normalization_flags(ac);
	float offset;
	float unitfac = ANIM_unit_mapping_get_factor(ac->scene, id, fcu, mapping_flag, &offset);

	/* for now, only show when debugging driver... */
	//if ((driver->flag & DRIVER_FLAG_SHOWDEBUG) == 0)
	//	return;

	const uint shdr_pos = GWN_vertformat_attr_add(immVertexFormat(), "pos", GWN_COMP_F32, 2, GWN_FETCH_FLOAT);
	immBindBuiltinProgram(GPU_SHADER_2D_LINE_DASHED_UNIFORM_COLOR);

	float viewport_size[4];
	GPU_viewport_size_get_f(viewport_size);
	immUniform2f("viewport_size", viewport_size[2] / UI_DPI_FAC, viewport_size[3] / UI_DPI_FAC);

	immUniform1i("colors_len", 0);  /* Simple dashes. */

	/* No curve to modify/visualize the result?
	 * => We still want to show the 1-1 default...
	 */
	if ((fcu->totvert == 0) && BLI_listbase_is_empty(&fcu->modifiers)) {
		float t;

		/* draw with thin dotted lines in style of what curve would have been */
		immUniformColor3fv(fcu->color);

		immUniform1f("dash_width", 40.0f);
		immUniform1f("dash_factor", 0.5f);
		GPU_line_width(2.0f);

		/* draw 1-1 line, stretching just past the screen limits
		 * NOTE: we need to scale the y-values to be valid for the units
		 */
		immBegin(GWN_PRIM_LINES, 2);

		t = v2d->cur.xmin;
		immVertex2f(shdr_pos, t, (t + offset) * unitfac);

		t = v2d->cur.xmax;
		immVertex2f(shdr_pos, t, (t + offset) * unitfac);

		immEnd();
	}

	/* draw driver only if actually functional */
	if ((driver->flag & DRIVER_FLAG_INVALID) == 0) {
		/* grab "coordinates" for driver outputs */
		float x = driver->curval;
		float y = fcu->curval * unitfac;

		/* only draw indicators if the point is in range*/
		if (x >= v2d->cur.xmin) {
			float co[2];

			/* draw dotted lines leading towards this point from both axes ....... */
			immUniformColor3f(0.9f, 0.9f, 0.9f);
			immUniform1f("dash_width", 10.0f);
			immUniform1f("dash_factor", 0.5f);

			immBegin(GWN_PRIM_LINES, (y >= v2d->cur.ymin) ? 4 : 2);

			/* x-axis lookup */
			co[0] = x;

			if (y >= v2d->cur.ymin) {
				co[1] = v2d->cur.ymin - 1.0f;
				immVertex2fv(shdr_pos, co);

				co[1] = y;
				immVertex2fv(shdr_pos, co);
			}

			/* y-axis lookup */
			co[1] = y;

			co[0] = v2d->cur.xmin - 1.0f;
			immVertex2fv(shdr_pos, co);

			co[0] = x;
			immVertex2fv(shdr_pos, co);

			immEnd();

			immUnbindProgram();

			/* GWN_PRIM_POINTS do not survive dashed line geometry shader... */
			immBindBuiltinProgram(GPU_SHADER_2D_UNIFORM_COLOR);

			/* x marks the spot .................................................... */
			/* -> outer frame */
			immUniformColor3f(0.9f, 0.9f, 0.9f);
			GPU_point_size(7.0);

			immBegin(GWN_PRIM_POINTS, 1);
			immVertex2f(shdr_pos, x, y);
			immEnd();

			/* inner frame */
			immUniformColor3f(0.9f, 0.0f, 0.0f);
			GPU_point_size(3.0);

			immBegin(GWN_PRIM_POINTS, 1);
			immVertex2f(shdr_pos, x, y);
			immEnd();
		}
	}

	immUnbindProgram();
}

/* Public Curve-Drawing API  ---------------- */

/* Draw the 'ghost' F-Curves (i.e. snapshots of the curve)
 * NOTE: unit mapping has already been applied to the values, so do not try and apply again
 */
void graph_draw_ghost_curves(bAnimContext *ac, SpaceIpo *sipo, ARegion *ar)
{
	FCurve *fcu;

	/* draw with thick dotted lines */
	GPU_line_width(3.0f);

	/* anti-aliased lines for less jagged appearance */
	if ((sipo->flag & SIPO_BEAUTYDRAW_OFF) == 0) {
		GPU_line_smooth(true);
	}
	GPU_blend(true);

	const uint shdr_pos = GWN_vertformat_attr_add(immVertexFormat(), "pos", GWN_COMP_F32, 2, GWN_FETCH_FLOAT);

	immBindBuiltinProgram(GPU_SHADER_2D_LINE_DASHED_UNIFORM_COLOR);

	float viewport_size[4];
	GPU_viewport_size_get_f(viewport_size);
	immUniform2f("viewport_size", viewport_size[2] / UI_DPI_FAC, viewport_size[3] / UI_DPI_FAC);

	immUniform1i("colors_len", 0);  /* Simple dashes. */
	immUniform1f("dash_width", 20.0f);
	immUniform1f("dash_factor", 0.5f);

	/* the ghost curves are simply sampled F-Curves stored in sipo->ghostCurves */
	for (fcu = sipo->ghostCurves.first; fcu; fcu = fcu->next) {
		/* set whatever color the curve has set
		 *  - this is set by the function which creates these
		 *	- draw with a fixed opacity of 2
		 */
		immUniformColor3fvAlpha(fcu->color, 0.5f);

		/* simply draw the stored samples */
		draw_fcurve_curve_samples(ac, NULL, fcu, &ar->v2d, shdr_pos);
	}

	immUnbindProgram();

	if ((sipo->flag & SIPO_BEAUTYDRAW_OFF) == 0) {
		GPU_line_smooth(false);
	}
	GPU_blend(false);
}

/* This is called twice from space_graph.c -> graph_main_region_draw()
 * Unselected then selected F-Curves are drawn so that they do not occlude each other.
 */
void graph_draw_curves(bAnimContext *ac, SpaceIpo *sipo, ARegion *ar, View2DGrid *grid, short sel)
{
	ListBase anim_data = {NULL, NULL};
	bAnimListElem *ale;
	int filter;

	/* build list of curves to draw */
	filter = (ANIMFILTER_DATA_VISIBLE | ANIMFILTER_CURVE_VISIBLE);
	filter |= ((sel) ? (ANIMFILTER_SEL) : (ANIMFILTER_UNSEL));
	ANIM_animdata_filter(ac, &anim_data, filter, ac->data, ac->datatype);

	/* for each curve:
	 *	draw curve, then handle-lines, and finally vertices in this order so that
	 *  the data will be layered correctly
	 */
	for (ale = anim_data.first; ale; ale = ale->next) {
		FCurve *fcu = (FCurve *)ale->key_data;
		FModifier *fcm = find_active_fmodifier(&fcu->modifiers);
		AnimData *adt = ANIM_nla_mapping_get(ac, ale);

		/* map keyframes for drawing if scaled F-Curve */
		if (adt) {
			ANIM_nla_mapping_apply_fcurve(adt, ale->key_data, 0, 0);
		}

		/* draw curve:
		 *	- curve line may be result of one or more destructive modifiers or just the raw data,
		 *	  so we need to check which method should be used
		 *	- controls from active modifier take precedence over keyframes
		 *	  (XXX! editing tools need to take this into account!)
		 */

		/* 1) draw curve line */
		if (((fcu->modifiers.first) || (fcu->flag & FCURVE_INT_VALUES)) ||
		    (((fcu->bezt) || (fcu->fpt)) && (fcu->totvert)))
		{
			/* set color/drawing style for curve itself */
			/* draw active F-Curve thicker than the rest to make it stand out */
			if (fcu->flag & FCURVE_ACTIVE) {
				GPU_line_width(2.5);
			}
			else {
				GPU_line_width(1.0);
			}

			/* anti-aliased lines for less jagged appearance */
			if ((sipo->flag & SIPO_BEAUTYDRAW_OFF) == 0) {
				GPU_line_smooth(true);
			}
			GPU_blend(true);

			const uint shdr_pos = GWN_vertformat_attr_add(immVertexFormat(), "pos", GWN_COMP_F32, 2, GWN_FETCH_FLOAT);

			immBindBuiltinProgram(GPU_SHADER_2D_LINE_DASHED_UNIFORM_COLOR);

			float viewport_size[4];
			GPU_viewport_size_get_f(viewport_size);
			immUniform2f("viewport_size", viewport_size[2] / UI_DPI_FAC, viewport_size[3] / UI_DPI_FAC);

			immUniform1i("colors_len", 0);  /* Simple dashes. */

			if (BKE_fcurve_is_protected(fcu)) {
				/* protected curves (non editable) are drawn with dotted lines */
				immUniform1f("dash_width", 4.0f);
				immUniform1f("dash_factor", 0.5f);
			}
			else {
				immUniform1f("dash_factor", 2.0f);  /* solid line */
			}

			if (((fcu->grp) && (fcu->grp->flag & AGRP_MUTED)) || (fcu->flag & FCURVE_MUTED)) {
				/* muted curves are drawn in a grayish hue */
				/* XXX should we have some variations? */
				immUniformThemeColorShade(TH_HEADER, 50);
			}
			else {
				/* set whatever color the curve has set
				 *	- unselected curves draw less opaque to help distinguish the selected ones
				 */
				immUniformColor3fvAlpha(fcu->color, fcurve_display_alpha(fcu));
			}

			/* draw F-Curve */
			if ((fcu->modifiers.first) || (fcu->flag & FCURVE_INT_VALUES)) {
				/* draw a curve affected by modifiers or only allowed to have integer values
				 * by sampling it at various small-intervals over the visible region
				 */
				draw_fcurve_curve(ac, ale->id, fcu, &ar->v2d, grid, shdr_pos);
			}
			else if (((fcu->bezt) || (fcu->fpt)) && (fcu->totvert)) {
				/* just draw curve based on defined data (i.e. no modifiers) */
				if (fcu->bezt) {
					if (fcurve_can_use_simple_bezt_drawing(fcu)) {
						draw_fcurve_curve_bezts(ac, ale->id, fcu, &ar->v2d, shdr_pos);
					}
					else {
						draw_fcurve_curve(ac, ale->id, fcu, &ar->v2d, grid, shdr_pos);
					}
				}
				else if (fcu->fpt) {
					draw_fcurve_curve_samples(ac, ale->id, fcu, &ar->v2d, shdr_pos);
				}
			}

			immUnbindProgram();

			if ((sipo->flag & SIPO_BEAUTYDRAW_OFF) == 0) {
				GPU_line_smooth(false);
			}
			GPU_blend(false);
		}

		/* 2) draw handles and vertices as appropriate based on active
		 *	- if the option to only show controls if the F-Curve is selected is enabled, we must obey this
		 */
		if (!(sipo->flag & SIPO_SELCUVERTSONLY) || (fcu->flag & FCURVE_SELECTED)) {
			if (!fcurve_are_keyframes_usable(fcu) && !(fcu->fpt && fcu->totvert)) {
				/* only draw controls if this is the active modifier */
				if ((fcu->flag & FCURVE_ACTIVE) && (fcm)) {
					switch (fcm->type) {
						case FMODIFIER_TYPE_ENVELOPE: /* envelope */
							draw_fcurve_modifier_controls_envelope(fcm, &ar->v2d);
							break;
					}
				}
			}
			else if (((fcu->bezt) || (fcu->fpt)) && (fcu->totvert)) {
				short mapping_flag = ANIM_get_normalization_flags(ac);
				float offset;
				float unit_scale = ANIM_unit_mapping_get_factor(ac->scene, ale->id, fcu, mapping_flag, &offset);

				/* apply unit-scaling to all values via OpenGL */
				gpuPushMatrix();
				gpuScale2f(1.0f, unit_scale);
				gpuTranslate2f(0.0f, offset);

				/* set this once and for all - all handles and handle-verts should use the same thickness */
				GPU_line_width(1.0);

				if (fcu->bezt) {
					bool do_handles = draw_fcurve_handles_check(sipo, fcu);

					if (do_handles) {
						/* only draw handles/vertices on keyframes */
						GPU_blend(true);
						draw_fcurve_handles(sipo, fcu);
						GPU_blend(false);
					}

					draw_fcurve_vertices(ar, fcu, do_handles, (sipo->flag & SIPO_SELVHANDLESONLY));
				}
				else {
					/* samples: only draw two indicators at either end as indicators */
					draw_fcurve_samples(sipo, ar, fcu);
				}

				gpuPopMatrix();
			}
		}

		/* 3) draw driver debugging stuff */
		if ((ac->datatype == ANIMCONT_DRIVERS) && (fcu->flag & FCURVE_ACTIVE)) {
			graph_draw_driver_debug(ac, ale->id, fcu);
		}

		/* undo mapping of keyframes for drawing if scaled F-Curve */
		if (adt)
			ANIM_nla_mapping_apply_fcurve(adt, ale->key_data, 1, 0);
	}

	/* free list of curves */
	ANIM_animdata_freelist(&anim_data);
}

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

/* left hand part */
void graph_draw_channel_names(bContext *C, bAnimContext *ac, ARegion *ar)
{
	ListBase anim_data = {NULL, NULL};
	bAnimListElem *ale;
	int filter;

	View2D *v2d = &ar->v2d;
	float y = 0.0f, height;
	size_t items;
	int i = 0;

	/* 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 ACHANNEL_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 = (float)((items * ACHANNEL_STEP(ac)) + (ACHANNEL_HEIGHT(ac) * 2));
	UI_view2d_totRect_set(v2d, BLI_rcti_size_x(&ar->v2d.mask), height);

	/* loop through channels, and set up drawing depending on their type  */
	{   /* first pass: just the standard GL-drawing for backdrop + text */
		size_t channel_index = 0;

		y = (float)ACHANNEL_FIRST(ac);

		for (ale = anim_data.first, i = 0; ale; ale = ale->next, i++) {
			const float yminc = (float)(y - ACHANNEL_HEIGHT_HALF(ac));
			const float ymaxc = (float)(y + ACHANNEL_HEIGHT_HALF(ac));

			/* 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, channel_index);
			}

			/* adjust y-position for next one */
			y -= ACHANNEL_STEP(ac);
			channel_index++;
		}
	}
	{   /* second pass: widgets */
		uiBlock *block = UI_block_begin(C, ar, __func__, UI_EMBOSS);
		size_t channel_index = 0;

		y = (float)ACHANNEL_FIRST(ac);

		/* set blending again, as may not be set in previous step */
		GPU_blend_set_func_separate(GPU_SRC_ALPHA, GPU_ONE_MINUS_SRC_ALPHA, GPU_ONE, GPU_ONE_MINUS_SRC_ALPHA);
		GPU_blend(true);

		for (ale = anim_data.first, i = 0; ale; ale = ale->next, i++) {
			const float yminc = (float)(y - ACHANNEL_HEIGHT_HALF(ac));
			const float ymaxc = (float)(y + ACHANNEL_HEIGHT_HALF(ac));

			/* 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 -= ACHANNEL_STEP(ac);
			channel_index++;
		}

		UI_block_end(C, block);
		UI_block_draw(C, block);

		GPU_blend(false);
	}

	/* free tempolary channels */
	ANIM_animdata_freelist(&anim_data);
}