Cleanup: outdated IPO references in comments

source/blender/blenkernel/intern/colorband.c

@@ -490,7 +490,7 @@ bool BKE_colorband_evaluate(const ColorBand *coba, float in, float out[4])
       }
 
       if (ELEM(ipotype, COLBAND_INTERP_B_SPLINE, COLBAND_INTERP_CARDINAL)) {
-        /* ipo from right to left: 3 2 1 0 */
+        /* Interpolate from right to left: `3 2 1 0`. */
         float t[4];
 
         if (a >= coba->tot - 1) {

source/blender/blenkernel/intern/colortools.c

@@ -638,7 +638,7 @@ static void curvemap_make_table(const CurveMapping *cumap, CurveMap *cuma)
   cuma->mintable = clipr->xmin;
   cuma->maxtable = clipr->xmax;
 
-  /* hrmf... we now rely on blender ipo beziers, these are more advanced */
+  /* Rely on Blender interpolation for bezier curves, support extra functionality here as well. */
   bezt = MEM_callocN(cuma->totpoint * sizeof(BezTriple), "beztarr");
 
   for (int a = 0; a < cuma->totpoint; a++) {

source/blender/blenkernel/intern/key.c

@@ -315,11 +315,11 @@ Key *BKE_key_add(Main *bmain, ID *id) /* common function */
   return key;
 }
 
-/* Sort shape keys and Ipo curves after a change.  This assumes that at most
- * one key was moved, which is a valid assumption for the places it's
- * currently being called.
+/**
+ * Sort shape keys after a change.
+ * This assumes that at most one key was moved,
+ * which is a valid assumption for the places it's currently being called.
  */
-
 void BKE_key_sort(Key *key)
 {
   KeyBlock *kb;

source/blender/editors/space_sequencer/sequencer_edit.c

@@ -1816,8 +1816,8 @@ static int sequencer_separate_images_exec(bContext *C, wmOperator *op)
       /* Remove seq so overlap tests don't conflict,
        * see seq_free_sequence below for the real freeing. */
       BLI_remlink(ed->seqbasep, seq);
-      /* if (seq->ipo) id_us_min(&seq->ipo->id); */
-      /* XXX, remove fcurve and assign to split image strips */
+      /* TODO: remove f-curve and assign to split image strips.
+       * The old animation system would remove the user of `seq->ipo`. */
 
       start_ofs = timeline_frame = SEQ_transform_get_left_handle_frame(seq);
       frame_end = SEQ_transform_get_right_handle_frame(seq);

source/blender/editors/transform/transform_convert_action.c

@@ -210,12 +210,13 @@ static TransData *ActionFCurveToTransData(TransData *td,
   return td;
 }
 
-/* This function advances the address to which td points to, so it must return
+/**
+ * This function advances the address to which td points to, so it must return
  * the new address so that the next time new transform data is added, it doesn't
- * overwrite the existing ones...  i.e.   td = GPLayerToTransData(td, ipo, ob, side, cfra);
+ * overwrite the existing ones: e.g. `td += GPLayerToTransData(td, ...);`
  *
- * The 'side' argument is needed for the extend mode. 'B' = both sides, 'R'/'L' mean only data
- * on the named side are used.
+ * \param side: is needed for the extend mode. 'B' = both sides,
+ * 'R'/'L' mean only data on the named side are used.
  */
 static int GPLayerToTransData(TransData *td,
                               tGPFtransdata *tfd,
@@ -242,7 +243,7 @@ static int GPLayerToTransData(TransData *td,
         tfd->val = (float)gpf->framenum;
         tfd->sdata = &gpf->framenum;
 
-        /* advance td now */
+        /* Advance `td` now. */
         td++;
         tfd++;
         count++;
@@ -339,7 +340,7 @@ void createTransActionData(bContext *C, TransInfo *t)
     t->frame_side = 'B';
   }
 
-  /* loop 1: fully select ipo-keys and count how many BezTriples are selected */
+  /* loop 1: fully select F-curve keys and count how many BezTriples are selected */
   for (ale = anim_data.first; ale; ale = ale->next) {
     AnimData *adt = ANIM_nla_mapping_get(&ac, ale);
     int adt_count = 0;

source/blender/editors/util/ed_util.c

@@ -295,8 +295,11 @@ bool ED_editors_flush_edits(Main *bmain)
 
 /* ***** XXX: functions are using old blender names, cleanup later ***** */
 
-/* now only used in 2d spaces, like time, ipo, nla, sima... */
-/* XXX shift/ctrl not configurable */
+/**
+ * Now only used in 2D spaces, like time, f-curve, NLA, image, etc.
+ *
+ * \note Shift/Control are not configurable key-bindings.
+ */
 void apply_keyb_grid(
     int shift, int ctrl, float *val, float fac1, float fac2, float fac3, int invert)
 {