text: /*
   * 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
   */
  
  /** \file
   * \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 "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 = GPU_vertformat_attr_add(
        immVertexFormat(), "pos", GPU_COMP_F32, 2, GPU_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(GPU_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(GPU_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(GPU_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(GPU_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 = GPU_vertformat_attr_add(immVertexFormat(), "pos", GPU_COMP_F32, 2, GPU_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(SpaceGraph *sipo, FCurve *fcu)
  {
    /* don't draw handle lines if handles are not to be shown */
    if (
        /* handles shouldn't be shown anywhere */
        (sipo->flag & SIPO_NOHANDLES) ||
        /* keyframes aren't editable */
        (fcu->flag & FCURVE_PROTECTED) ||
  #if 0 /* handles can still be selected and handle types set, better draw - campbell */
        /* editing the handles here will cause weird/incorrect interpolation issues */
        (fcu->flag & FCURVE_INT_VALUES) ||
  #endif
        /* group that curve belongs to is not editable */
        ((fcu->grp) && (fcu->grp->flag & AGRP_PROTECTED)) ||
        /* Do not show handles if there is only 1 keyframe,
         * otherwise they all clump together in an ugly ball. */
        (fcu->totvert <= 1)) {
      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(SpaceGraph *sipo, FCurve *fcu)
  {
    int sel, b;
  
    GPUVertFormat *format = immVertexFormat();
    uint pos = GPU_vertformat_attr_add(format, "pos", GPU_COMP_F32, 2, GPU_FETCH_FLOAT);
    uint color = GPU_vertformat_attr_add(
        format, "color", GPU_COMP_U8, 4, GPU_FETCH_INT_TO_FLOAT_UNIT);
    immBindBuiltinProgram(GPU_SHADER_2D_FLAT_COLOR);
  
    immBeginAtMost(GPU_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;
            immAttr4ubv(color, col);
            immVertex2fv(pos, fp);
            immAttr4ubv(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;
            immAttr4ubv(color, col);
            immVertex2fv(pos, fp + 3);
            immAttr4ubv(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;
            immAttr4ubv(color, col);
            immVertex2fv(pos, fp);
            immAttr4ubv(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;
            immAttr4ubv(color, col);
            immVertex2fv(pos, fp);
            immAttr4ubv(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 */
    GPU_matrix_push();
    GPU_matrix_translate_2f(x, y);
    GPU_matrix_scale_2f(1.0f / xscale * hsize, 1.0f / yscale * hsize);
  
    /* draw X shape */
    immBegin(GPU_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 */
    GPU_matrix_pop();
  }
  
  /* helper func - draw keyframe vertices only for an F-Curve */
  static void draw_fcurve_samples(SpaceGraph *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 = GPU_vertformat_attr_add(immVertexFormat(), "pos", GPU_COMP_F32, 2, GPU_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, unsigned int pos)
  {
    SpaceGraph *sipo = (SpaceGraph *)ac->sl;
    float samplefreq;
    float stime, etime;
    float unitFac, offset;
    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. */
    if (UI_view2d_scale_get_x(v2d) <= 0.0f) {
      return;
    }
  
    /* disable any drivers */
    FCurve fcurve_for_draw = *fcu_;
    fcurve_for_draw.driver = NULL;
  
    /* compute unit correction factor */
    unitFac = ANIM_unit_mapping_get_factor(ac->scene, id, &fcurve_for_draw, 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...
     */
  
    /* TODO: perhaps we should have 1.0 frames
     * as upper limit so that curves don't get too distorted? */
    float pixels_per_sample = 1.5f;
    samplefreq = pixels_per_sample / UI_view2d_scale_get_x(v2d);
  
    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(GPU_PRIM_LINE_STRIP, (n + 1));
  
      for (i = 0; i <= n; i++) {
        float ctime = stime + i * samplefreq;
        immVertex2f(pos, ctime, (evaluate_fcurve(&fcurve_for_draw, ctime) + offset) * unitFac);
      }
  
      immEnd();
    }
  }
  
  /* 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 */
    GPU_matrix_push();
    unit_scale = ANIM_unit_mapping_get_factor(ac->scene, id, fcu, mapping_flag, &offset);
    GPU_matrix_scale_2f(1.0f, unit_scale);
    GPU_matrix_translate_2f(0.0f, offset);
  
    immBegin(GPU_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();
  
    GPU_matrix_pop();
  }
  
  /* 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 */
    GPU_matrix_push();
    unit_scale = ANIM_unit_mapping_get_factor(ac->scene, id, fcu, mapping_flag, &offset);
    GPU_matrix_scale_2f(1.0f, unit_scale);
    GPU_matrix_translate_2f(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(GPU_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();
  
    GPU_matrix_pop();
  }
  
  /* 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 = GPU_vertformat_attr_add(
        immVertexFormat(), "pos", GPU_COMP_F32, 2, GPU_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(GPU_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(GPU_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();
  
        /* GPU_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(GPU_PRIM_POINTS, 1);
        immVertex2f(shdr_pos, x, y);
        immEnd();
  
        /* inner frame */
        immUniformColor3f(0.9f, 0.0f, 0.0f);
        GPU_point_size(3.0);
  
        immBegin(GPU_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, SpaceGraph *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 = GPU_vertformat_attr_add(
        immVertexFormat(), "pos", GPU_COMP_F32, 2, GPU_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->runtime.ghost_curves */
    for (fcu = sipo->runtime.ghost_curves.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, SpaceGraph *sipo, ARegion *ar, 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 = GPU_vertformat_attr_add(
            immVertexFormat(), "pos", GPU_COMP_F32, 2, GPU_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, 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, 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 */
          GPU_matrix_push();
          GPU_matrix_scale_2f(1.0f, unit_scale);
          GPU_matrix_translate_2f(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);
          }
  
          GPU_matrix_pop();
        }
      }
  
      /* 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 height;
    size_t items;
  
    /* 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 */
    height = ACHANNEL_TOT_HEIGHT(ac, items);
    v2d->tot.ymin = -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;
      float ymax = ACHANNEL_FIRST_TOP(ac);
  
      for (ale = anim_data.first; ale; ale = ale->next, ymax -= ACHANNEL_STEP(ac), channel_index++) {
        float ymin = ymax - ACHANNEL_HEIGHT(ac);
  
        /* check if visible */
        if (IN_RANGE(ymin, v2d->cur.ymin, v2d->cur.ymax) ||
            IN_RANGE(ymax, v2d->cur.ymin, v2d->cur.ymax)) {
          /* draw all channels using standard channel-drawing API */
          ANIM_channel_draw(ac, ale, ymin, ymax, channel_index);
        }
      }
    }
    { /* second pass: widgets */
      uiBlock *block = UI_block_begin(C, ar, __func__, UI_EMBOSS);
      size_t channel_index = 0;
      float ymax = ACHANNEL_FIRST_TOP(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; ale; ale = ale->next, ymax -= ACHANNEL_STEP(ac), channel_index++) {
        float ymin = ymax - ACHANNEL_HEIGHT(ac);
  
        /* check if visible */
        if (IN_RANGE(ymin, v2d->cur.ymin, v2d->cur.ymax) ||
            IN_RANGE(ymax, v2d->cur.ymin, v2d->cur.ymax)) {
          /* draw all channels using standard channel-drawing API */
          rctf channel_rect;
          BLI_rctf_init(&channel_rect, 0, v2d->cur.xmax - V2D_SCROLL_WIDTH, ymin, ymax);
          ANIM_channel_draw_widgets(C, ac, ale, block, &channel_rect, channel_index);
        }
      }
  
      UI_block_end(C, block);
      UI_block_draw(C, block);
  
      GPU_blend(false);
    }
  
    /* free tempolary channels */
    ANIM_animdata_freelist(&anim_data);
  }
  