graph_draw.c

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

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

#ifndef _WIN32
#include <unistd.h>
#else
#include <io.h>
#endif


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

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

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


#include "BIF_gl.h"
#include "BIF_glutil.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
 */
#define drawFCurveFade(fcu) ( ((fcu)->flag & FCURVE_SELECTED)? 1.0f : 0.25f )

/* set the color for some point from some value given packed into an int 
 *  - intV: integer value containing color info packed into an int
 *  - alpha: float value describing the 
 */
#define cpackA(intVC, alpha)                                                  \
    {                                                                         \
        float _cpackCol[3];                                                   \
        cpack_to_rgb(intVC, &_cpackCol[0], &_cpackCol[1], &_cpackCol[2]);     \
        glColor4f(_cpackCol[0], _cpackCol[1], _cpackCol[2], 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 * (v2d->cur.xmax - v2d->cur.xmin);
    int i;
    
    /* draw two black lines showing the standard reference levels */
    glColor3f(0.0f, 0.0f, 0.0f);
    setlinestyle(5);
    
    glBegin(GL_LINES);
        glVertex2f(v2d->cur.xmin, env->midval+env->min);
        glVertex2f(v2d->cur.xmax, env->midval+env->min);
        
        glVertex2f(v2d->cur.xmin, env->midval+env->max);
        glVertex2f(v2d->cur.xmax, env->midval+env->max);
    glEnd(); // GL_LINES
    setlinestyle(0);
    
    /* set size of vertices (non-adjustable for now) */
    glPointSize(2.0f);
    
    // for now, point color is fixed, and is white
    glColor3f(1.0f, 1.0f, 1.0f);
    
    /* we use bgl points not standard gl points, to workaround vertex 
     * drawing bugs that some drivers have (probably legacy ones only though)
     */
    bglBegin(GL_POINTS);
    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)) {
            glVertex2f(fed->time, fed->min);
            glVertex2f(fed->time, fed->max);
        }
    }
    bglEnd(); // GL_POINTS
    
    glPointSize(1.0f);
}

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

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

/* helper func - draw keyframe vertices only for an F-Curve */
static void draw_fcurve_vertices_keyframes (FCurve *fcu, SpaceIpo *UNUSED(sipo), View2D *v2d, short edit, short sel)
{
    BezTriple *bezt= fcu->bezt;
    const float fac= 0.05f * (v2d->cur.xmax - v2d->cur.xmin);
    int i;
    
    /* we use bgl points not standard gl points, to workaround vertex 
     * drawing bugs that some drivers have (probably legacy ones only though)
     */
    bglBegin(GL_POINTS);
    
    for (i = 0; i < fcu->totvert; i++, bezt++) {
        /* as an optimisation 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)
                    bglVertex3fv(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
                bglVertex3fv(bezt->vec[1]);
            }
        }
    }
    
    bglEnd(); // GL_POINTS
}


/* helper func - draw handle vertex for an F-Curve as a round unfilled circle 
 * 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_handle_control (float x, float y, float xscale, float yscale, float hsize)
{
    static GLuint displist=0;
    
    /* initialise round circle shape */
    if (displist == 0) {
        GLUquadricObj *qobj;
        
        displist= glGenLists(1);
        glNewList(displist, GL_COMPILE);
        
        qobj    = gluNewQuadric(); 
        gluQuadricDrawStyle(qobj, GLU_SILHOUETTE); 
        gluDisk(qobj, 0,  0.7, 8, 1);
        gluDeleteQuadric(qobj);  
        
        glEndList();
    }
    
    /* adjust view transform before starting */
    glTranslatef(x, y, 0.0f);
    glScalef(1.0f/xscale*hsize, 1.0f/yscale*hsize, 1.0f);
    
    /* draw! */
    glCallList(displist);
    
    /* restore view transform */
    glScalef(xscale/hsize, yscale/hsize, 1.0);
    glTranslatef(-x, -y, 0.0f);
}

/* helper func - draw handle vertices only for an F-Curve (if it is not protected) */
static void draw_fcurve_vertices_handles (FCurve *fcu, SpaceIpo *sipo, View2D *v2d, short sel, short sel_handle_only)
{
    BezTriple *bezt= fcu->bezt;
    BezTriple *prevbezt = NULL;
    float hsize, xscale, yscale;
    int i;
    
    /* get view settings */
    hsize= UI_GetThemeValuef(TH_HANDLE_VERTEX_SIZE);
    UI_view2d_getscale(v2d, &xscale, &yscale);
    
    /* set handle color */
    if (sel) UI_ThemeColor(TH_HANDLE_VERTEX_SELECT);
    else UI_ThemeColor(TH_HANDLE_VERTEX);
    
    /* anti-aliased lines for more consistent appearance */
    if ((sipo->flag & SIPO_BEAUTYDRAW_OFF)==0) glEnable(GL_LINE_SMOOTH);
    glEnable(GL_BLEND);
    
    for (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 || BEZSELECTED(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)*/
                    draw_fcurve_handle_control(bezt->vec[0][0], bezt->vec[0][1], xscale, yscale, hsize);
            }
            
            if (bezt->ipo==BEZT_IPO_BEZ) {
                if ((bezt->f3 & SELECT) == sel)/* && v2d->cur.xmin < bezt->vec[2][0] < v2d->cur.xmax)*/
                    draw_fcurve_handle_control(bezt->vec[2][0], bezt->vec[2][1], xscale, yscale, hsize);
            }
        }
    }
    
    if ((sipo->flag & SIPO_BEAUTYDRAW_OFF)==0) glDisable(GL_LINE_SMOOTH);
    glDisable(GL_BLEND);
}

/* helper func - set color to draw F-Curve data with */
static void set_fcurve_vertex_color (FCurve *fcu, short sel)
{
    /* Fade the 'intensity' of the vertices based on the selection of the curves too */
    int alphaOffset= (int)((drawFCurveFade(fcu) - 1.0f) * 255);
    
    /* 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 */
        if (sel) UI_ThemeColorShadeAlpha(TH_VERTEX_SELECT, 0, alphaOffset); 
        else UI_ThemeColorShadeAlpha(TH_VERTEX, 0, alphaOffset);
    } 
    else {
        /* Curve's points CANNOT BE edited */
        if (sel) UI_ThemeColorShadeAlpha(TH_TEXT_HI, 0, alphaOffset);
        else UI_ThemeColorShadeAlpha(TH_TEXT, 0, alphaOffset);
    }
}


static void draw_fcurve_vertices (SpaceIpo *sipo, ARegion *ar, FCurve *fcu, short do_handles, short sel_handle_only)
{
    View2D *v2d= &ar->v2d;
    
    /* only draw points if curve is visible 
     *  - draw unselected points before selected points as separate passes to minimise color-changing overhead
     *     (XXX dunno if this is faster than drawing all in one pass though) 
     *     and also 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)
     */
    
    glPointSize(UI_GetThemeValuef(TH_VERTEX_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)
    {
        set_fcurve_vertex_color(fcu, 0);
        draw_fcurve_vertices_handles(fcu, sipo, v2d, 0, sel_handle_only);
        
        set_fcurve_vertex_color(fcu, 1);
        draw_fcurve_vertices_handles(fcu, sipo, v2d, 1, sel_handle_only);
    }
        
    /* draw keyframes over the handles */
    set_fcurve_vertex_color(fcu, 0);
    draw_fcurve_vertices_keyframes(fcu, sipo, v2d, !(fcu->flag & FCURVE_PROTECTED), 0);
    
    set_fcurve_vertex_color(fcu, 1);
    draw_fcurve_vertices_keyframes(fcu, sipo, v2d, !(fcu->flag & FCURVE_PROTECTED), 1);
    
    glPointSize(1.0f);
}

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

static int 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 0;
    } 
    else 
    {
        return 1;
    }
}

/* 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;
    
    /* a single call to GL_LINES here around these calls should be sufficient to still
     * get separate line segments, but which aren't wrapped with GL_LINE_STRIP every time we
     * want a single line
     */
    glBegin(GL_LINES);
    
    /* 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;
        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 (BEZSELECTED(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]= drawFCurveFade(fcu) * 255;
                    glColor4ubv((GLubyte *)col);
                    
                    glVertex2fv(fp); glVertex2fv(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]= drawFCurveFade(fcu) * 255;
                    glColor4ubv((GLubyte *)col);
                    
                    glVertex2fv(fp+3); glVertex2fv(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]= drawFCurveFade(fcu) * 255;
                    glColor4ubv((GLubyte *)col);
                    
                    glVertex2fv(fp); glVertex2fv(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]= drawFCurveFade(fcu) * 255;
                    glColor4ubv((GLubyte *)col);
                    
                    glVertex2fv(fp); glVertex2fv(fp+3); 
                }
            }
        }
    }
    
    glEnd(); // GL_LINES 
}

/* 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)
{
    static GLuint displist=0;
    
    /* initialise X shape */
    if (displist == 0) {
        displist= glGenLists(1);
        glNewList(displist, GL_COMPILE);
        
        glBegin(GL_LINES);
            glVertex2f(-0.7f, -0.7f);
            glVertex2f(+0.7f, +0.7f);
            
            glVertex2f(-0.7f, +0.7f);
            glVertex2f(+0.7f, -0.7f);
        glEnd(); // GL_LINES
        
        glEndList();
    }
    
    /* adjust view transform before starting */
    glTranslatef(x, y, 0.0f);
    glScalef(1.0f/xscale*hsize, 1.0f/yscale*hsize, 1.0f);
    
    /* draw! */
    glCallList(displist);
    
    /* restore view transform */
    glScalef(xscale/hsize, yscale/hsize, 1.0);
    glTranslatef(-x, -y, 0.0f);
}

/* 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_getscale(&ar->v2d, &xscale, &yscale);
    
    /* set vertex color */
    if (fcu->flag & (FCURVE_ACTIVE|FCURVE_SELECTED)) UI_ThemeColor(TH_TEXT_HI);
    else UI_ThemeColor(TH_TEXT);
    
    /* 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) glEnable(GL_LINE_SMOOTH);
        glEnable(GL_BLEND);
        
        draw_fcurve_sample_control(first->vec[0], first->vec[1], xscale, yscale, hsize);
        draw_fcurve_sample_control(last->vec[0], last->vec[1], xscale, yscale, hsize);
        
        glDisable(GL_BLEND);
        if ((sipo->flag & SIPO_BEAUTYDRAW_OFF)==0) glDisable(GL_LINE_SMOOTH);
    }
}

/* 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)
{
    ChannelDriver *driver;
    float samplefreq, ctime;
    float stime, etime;
    float unitFac;
    float dx, dy;

    /* 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, 0);
    
    /* 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;
    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
     */
    glBegin(GL_LINE_STRIP);
    
    for (ctime= stime; ctime <= etime; ctime += samplefreq)
        glVertex2f( ctime, evaluate_fcurve(fcu, ctime)*unitFac );
    
    glEnd();
    
    /* 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)
{
    FPoint *prevfpt= fcu->fpt;
    FPoint *fpt= prevfpt + 1;
    float fac, v[2];
    int b= fcu->totvert-1;
    
    glBegin(GL_LINE_STRIP);
    
    /* apply unit mapping */
    ANIM_unit_mapping_apply_fcurve(ac->scene, id, fcu, 0);
    
    /* 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 dosnt 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]);
        }
        
        glVertex2fv(v);
    }
    
    /* if only one sample, add it now */
    if (fcu->totvert == 1)
        glVertex2fv(prevfpt->vec);
    
    /* 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) */
        glVertex2fv(prevfpt->vec);
        
        /* get next pointers */
        prevfpt= fpt; 
        fpt++;
        
        /* last point? */
        if (b == 0)
            glVertex2fv(prevfpt->vec);
    }
    
    /* 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 dosnt 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]);
        }
        
        glVertex2fv(v);
    }
    
    /* unapply unit mapping */
    ANIM_unit_mapping_apply_fcurve(ac->scene, id, fcu, ANIM_UNITCONV_RESTORE);
    
    glEnd();
}

/* helper func - draw one repeat of an F-Curve */
static void draw_fcurve_curve_bezts (bAnimContext *ac, ID *id, FCurve *fcu, View2D *v2d)
{
    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;
    
    glBegin(GL_LINE_STRIP);
    
    /* apply unit mapping */
    ANIM_unit_mapping_apply_fcurve(ac->scene, id, fcu, 0);
    
    /* 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]);
        }
        
        glVertex2fv(v1);
    }
    
    /* if only one keyframe, add it now */
    if (fcu->totvert == 1) {
        v1[0]= prevbezt->vec[1][0];
        v1[1]= prevbezt->vec[1][1];
        glVertex2fv(v1);
    }
    
    /* draw curve between first and last keyframe (if there are enough to do so) */
    // TODO: optimise 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];
            glVertex2fv(v1);
            
            v1[0]= bezt->vec[1][0];
            v1[1]= prevbezt->vec[1][1];
            glVertex2fv(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];
            glVertex2fv(v1);
        }
        else {
            /* 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];
                glVertex2fv(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);
                
                forward_diff_bezier(v1[0], v2[0], v3[0], v4[0], data, resol, sizeof(float)*3);
                forward_diff_bezier(v1[1], v2[1], v3[1], v4[1], data+1, resol, sizeof(float)*3);
                
                for (fp= data; resol; resol--, fp+= 3)
                    glVertex2fv(fp);
            }
        }
        
        /* get next pointers */
        prevbezt= bezt; 
        bezt++;
        
        /* last point? */
        if (b == 0) {
            v1[0]= prevbezt->vec[1][0];
            v1[1]= prevbezt->vec[1][1];
            glVertex2fv(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]);
        }
        
        glVertex2fv(v1);
    }
    
    /* unapply unit mapping */
    ANIM_unit_mapping_apply_fcurve(ac->scene, id, fcu, ANIM_UNITCONV_RESTORE);
    
    glEnd();
} 

/* 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 */
    setlinestyle(10);
    glLineWidth(3.0f);
    
    /* anti-aliased lines for less jagged appearance */
    if ((sipo->flag & SIPO_BEAUTYDRAW_OFF)==0) glEnable(GL_LINE_SMOOTH);
    glEnable(GL_BLEND);
    
    /* 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
         */
        glColor4f(fcu->color[0], fcu->color[1], fcu->color[2], 0.5f);
        
        /* simply draw the stored samples */
        draw_fcurve_curve_samples(ac, NULL, fcu, &ar->v2d);
    }
    
    /* restore settings */
    setlinestyle(0);
    glLineWidth(1.0f);
    
    if ((sipo->flag & SIPO_BEAUTYDRAW_OFF)==0) glDisable(GL_LINE_SMOOTH);
    glDisable(GL_BLEND);
}

/* This is called twice from space_graph.c -> graph_main_area_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 precidence over keyframes
         *    (XXX! editing tools need to take this into account!)
         */
         
        /* 1) draw curve line */
        {
            /* set color/drawing style for curve itself */
            if ( ((fcu->grp) && (fcu->grp->flag & AGRP_PROTECTED)) || (fcu->flag & FCURVE_PROTECTED) ) {
                /* protected curves (non editable) are drawn with dotted lines */
                setlinestyle(2);
            }
            if ( ((fcu->grp) && (fcu->grp->flag & AGRP_MUTED)) || (fcu->flag & FCURVE_MUTED) ) {
                /* muted curves are drawn in a greyish hue */
                // XXX should we have some variations?
                UI_ThemeColorShade(TH_HEADER, 50);
            }
            else {
                /* set whatever color the curve has set 
                 *  - unselected curves draw less opaque to help distinguish the selected ones
                 */
                glColor4f(fcu->color[0], fcu->color[1], fcu->color[2], drawFCurveFade(fcu));
            }
            
            /* draw active F-Curve thicker than the rest to make it stand out */
            if (fcu->flag & FCURVE_ACTIVE) {
                glLineWidth(2.0);
            }
            
            /* anti-aliased lines for less jagged appearance */
            if ((sipo->flag & SIPO_BEAUTYDRAW_OFF)==0) glEnable(GL_LINE_SMOOTH);
            glEnable(GL_BLEND);
            
            /* 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);
            }
            else if ( ((fcu->bezt) || (fcu->fpt)) && (fcu->totvert) ) { 
                /* just draw curve based on defined data (i.e. no modifiers) */
                if (fcu->bezt)
                    draw_fcurve_curve_bezts(ac, ale->id, fcu, &ar->v2d);
                else if (fcu->fpt)
                    draw_fcurve_curve_samples(ac, ale->id, fcu, &ar->v2d);
            }
            
            /* restore settings */
            setlinestyle(0);
            glLineWidth(1.0);
            
            if ((sipo->flag & SIPO_BEAUTYDRAW_OFF)==0) glDisable(GL_LINE_SMOOTH);
            glDisable(GL_BLEND);
        }
        
        /* 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) == 0) {
                /* 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) ) { 
                /* apply unit mapping */
                ANIM_unit_mapping_apply_fcurve(ac->scene, ale->id, fcu, 0);
                
                if (fcu->bezt) {
                    int do_handles = draw_fcurve_handles_check(sipo, fcu);
                    
                    if (do_handles) {
                        /* only draw handles/vertices on keyframes */
                        glEnable(GL_BLEND);
                        draw_fcurve_handles(sipo, fcu);
                        glDisable(GL_BLEND);
                    }
                    
                    draw_fcurve_vertices(sipo, 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);
                }
                
                /* unapply unit mapping */
                ANIM_unit_mapping_apply_fcurve(ac->scene, ale->id, fcu, ANIM_UNITCONV_RESTORE);
            }
        }
        
        /* 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 */
    BLI_freelistN(&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) + (ACHANNEL_HEIGHT*2));
    UI_view2d_totRect_set(v2d, ar->winx, height);
    
    /* loop through channels, and set up drawing depending on their type  */    
    {   /* first pass: just the standard GL-drawing for backdrop + text */
        y= (float)ACHANNEL_FIRST;
        
        for (ale= anim_data.first, i=0; ale; ale= ale->next, i++) {
            const float yminc= (float)(y - ACHANNEL_HEIGHT_HALF);
            const float ymaxc= (float)(y + ACHANNEL_HEIGHT_HALF);
            
            /* 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 -= ACHANNEL_STEP;
        }
    }
    {   /* second pass: widgets */
        uiBlock *block= uiBeginBlock(C, ar, __func__, UI_EMBOSS);
        size_t channel_index = 0;
        
        y= (float)ACHANNEL_FIRST;
        
        /* set blending again, as may not be set in previous step */
        glBlendFunc(GL_SRC_ALPHA, GL_ONE_MINUS_SRC_ALPHA);
        glEnable(GL_BLEND);
        
        for (ale= anim_data.first, i=0; ale; ale= ale->next, i++) {
            const float yminc= (float)(y - ACHANNEL_HEIGHT_HALF);
            const float ymaxc= (float)(y + ACHANNEL_HEIGHT_HALF);
            
            /* 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;
            channel_index++;
        }
        
        uiEndBlock(C, block);
        uiDrawBlock(C, block);
        
        glDisable(GL_BLEND);
    }
    
    /* free tempolary channels */
    BLI_freelistN(&anim_data);
}