Fix T81533: NLA Properly Draw FModifiers

When NLA strips weren't time-aligned with the underlying action, then
fcurve modifiers would not be drawn anchored to the strip. Fmodifiers
were evaluating properly, they just weren't drawn with the proper
offset and scale.

To fix it in this specific case, I've chosen to undo the keyframe
remapping then remap the draw-evaluation-time from scene time to
fcurve time. Afterward, I redo the keyframe remapping so the controls
are properly drawn.

The Envelope fmodifier has special drawing code which was fixed too. In
this case, no mapping at all was happening. The solution was similar,
to remap the envelope control points from fcurve time to scene time.

1 files changed, 41 insertions, 9 deletions

diff --git a/source/blender/editors/space_graph/graph_draw.c b/source/blender/editors/space_graph/graph_draw.c
index 2e33f3ef4c7..33e724459a9 100644
--- a/source/blender/editors/space_graph/graph_draw.c
+++ b/source/blender/editors/space_graph/graph_draw.c
@@ -35,9 +35,11 @@
 #include "DNA_userdef_types.h"
 #include "DNA_windowmanager_types.h"
 
+#include "BKE_anim_data.h"
 #include "BKE_context.h"
 #include "BKE_curve.h"
 #include "BKE_fcurve.h"
+#include "BKE_nla.h"
 
 #include "GPU_immediate.h"
 #include "GPU_matrix.h"
@@ -77,7 +79,12 @@ static float fcurve_display_alpha(FCurve *fcu)
 /* Envelope -------------- */
 
 /* TODO: draw a shaded poly showing the region of influence too!!! */
-static void draw_fcurve_modifier_controls_envelope(FModifier *fcm, View2D *v2d)
+/**
+ * \param adt_nla_remap: Send NULL if no NLA remapping necessary.
+ */
+static void draw_fcurve_modifier_controls_envelope(FModifier *fcm,
+                                                   View2D *v2d,
+                                                   AnimData *adt_nla_remap)
 {
   FMod_Envelope *env = (FMod_Envelope *)fcm->data;
   FCM_EnvelopeData *fed;
@@ -124,12 +131,15 @@ static void draw_fcurve_modifier_controls_envelope(FModifier *fcm, View2D *v2d)
     immBeginAtMost(GPU_PRIM_POINTS, env->totvert * 2);
 
     for (i = 0, fed = env->data; i < env->totvert; i++, fed++) {
+      const float env_scene_time = BKE_nla_tweakedit_remap(
+          adt_nla_remap, fed->time, NLATIME_CONVERT_MAP);
+
       /* 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);
+      if (IN_RANGE(env_scene_time, (v2d->cur.xmin - fac), (v2d->cur.xmax + fac))) {
+        immVertex2f(shdr_pos, env_scene_time, fed->min);
+        immVertex2f(shdr_pos, env_scene_time, fed->max);
       }
     }
 
@@ -572,7 +582,8 @@ static void draw_fcurve_samples(SpaceGraph *sipo, ARegion *region, FCurve *fcu)
 
 /* 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, uint pos)
+static void draw_fcurve_curve(
+    bAnimContext *ac, ID *id, FCurve *fcu_, View2D *v2d, uint pos, const bool use_nla_remap)
 {
   SpaceGraph *sipo = (SpaceGraph *)ac->sl;
   short mapping_flag = ANIM_get_normalization_flags(ac);
@@ -646,9 +657,17 @@ static void draw_fcurve_curve(bAnimContext *ac, ID *id, FCurve *fcu_, View2D *v2
   if (n > 0) {
     immBegin(GPU_PRIM_LINE_STRIP, (n + 1));
 
+    AnimData *adt = use_nla_remap ? BKE_animdata_from_id(id) : NULL;
+    /* NLA remapping is linear so we don't have to remap per iteration. */
+    const float eval_start = BKE_nla_tweakedit_remap(adt, stime, NLATIME_CONVERT_UNMAP);
+    const float eval_freq = BKE_nla_tweakedit_remap(
+                                adt, stime + samplefreq, NLATIME_CONVERT_UNMAP) -
+                            eval_start;
+
     for (int i = 0; i <= n; i++) {
       float ctime = stime + i * samplefreq;
-      immVertex2f(pos, ctime, (evaluate_fcurve(&fcurve_for_draw, ctime) + offset) * unitFac);
+      const float eval_time = eval_start + i * eval_freq;
+      immVertex2f(pos, ctime, (evaluate_fcurve(&fcurve_for_draw, eval_time) + offset) * unitFac);
     }
 
     immEnd();
@@ -1015,7 +1034,20 @@ static void draw_fcurve(bAnimContext *ac, SpaceGraph *sipo, ARegion *region, bAn
       /* 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, &region->v2d, shdr_pos);
+      if (adt) {
+        /** We have to do this mapping dance since the keyframes were remapped but the Fmodifier
+         * evaluations are not.
+         *
+         * So we undo the keyframe remapping and instead remap the evaluation time when drawing the
+         * curve itself. Afterward, we go back and redo the keyframe remapping so the controls are
+         * drawn properly. */
+        ANIM_nla_mapping_apply_fcurve(adt, ale->key_data, true, false);
+        draw_fcurve_curve(ac, ale->id, fcu, &region->v2d, shdr_pos, true);
+        ANIM_nla_mapping_apply_fcurve(adt, ale->key_data, false, false);
+      }
+      else {
+        draw_fcurve_curve(ac, ale->id, fcu, &region->v2d, shdr_pos, false);
+      }
     }
     else if (((fcu->bezt) || (fcu->fpt)) && (fcu->totvert)) {
       /* just draw curve based on defined data (i.e. no modifiers) */
@@ -1024,7 +1056,7 @@ static void draw_fcurve(bAnimContext *ac, SpaceGraph *sipo, ARegion *region, bAn
           draw_fcurve_curve_bezts(ac, ale->id, fcu, &region->v2d, shdr_pos);
         }
         else {
-          draw_fcurve_curve(ac, ale->id, fcu, &region->v2d, shdr_pos);
+          draw_fcurve_curve(ac, ale->id, fcu, &region->v2d, shdr_pos, false);
         }
       }
       else if (fcu->fpt) {
@@ -1050,7 +1082,7 @@ static void draw_fcurve(bAnimContext *ac, SpaceGraph *sipo, ARegion *region, bAn
       if ((fcu->flag & FCURVE_ACTIVE) && (fcm)) {
         switch (fcm->type) {
           case FMODIFIER_TYPE_ENVELOPE: /* envelope */
-            draw_fcurve_modifier_controls_envelope(fcm, &region->v2d);
+            draw_fcurve_modifier_controls_envelope(fcm, &region->v2d, adt);
             break;
         }
       }