diff --git a/source/blender/blenkernel/BKE_key.hh b/source/blender/blenkernel/BKE_key.hh
index 7721bbe7fc9..f563ccced81 100644
--- a/source/blender/blenkernel/BKE_key.hh
+++ b/source/blender/blenkernel/BKE_key.hh
@@ -11,6 +11,8 @@
 #include "BLI_math_vector_types.hh"
 #include "BLI_span.hh"
 
+#include "DNA_key_types.h"
+
 /** \file
  * \ingroup bke
  */
@@ -33,15 +35,15 @@ Key *BKE_key_add(Main *bmain, ID *id);
  */
 void BKE_key_sort(Key *key);
 
-void key_curve_position_weights(float t, float data[4], int type);
+void key_curve_position_weights(float t, float data[4], KeyInterpolationType type);
 /**
  * First derivative.
  */
-void key_curve_tangent_weights(float t, float data[4], int type);
+void key_curve_tangent_weights(float t, float data[4], KeyInterpolationType type);
 /**
  * Second derivative.
  */
-void key_curve_normal_weights(float t, float data[4], int type);
+void key_curve_normal_weights(float t, float data[4], KeyInterpolationType type);
 
 /**
  * Returns key coordinates (+ tilt) when key applied, NULL otherwise.
diff --git a/source/blender/blenkernel/intern/curve.cc b/source/blender/blenkernel/intern/curve.cc
index ed6280ab427..52368104d86 100644
--- a/source/blender/blenkernel/intern/curve.cc
+++ b/source/blender/blenkernel/intern/curve.cc
@@ -1972,7 +1972,7 @@ static void tilt_bezpart(const BezTriple *prevbezt,
                       (bezt->tilt - prevbezt->tilt) * (3.0f * fac * fac - 2.0f * fac * fac * fac);
       }
       else {
-        key_curve_position_weights(fac, t, nu->tilt_interp);
+        key_curve_position_weights(fac, t, KeyInterpolationType(nu->tilt_interp));
         *tilt_array = t[0] * pprev->tilt + t[1] * prevbezt->tilt + t[2] * bezt->tilt +
                       t[3] * next->tilt;
       }
@@ -1992,7 +1992,7 @@ static void tilt_bezpart(const BezTriple *prevbezt,
 
         /* reuse interpolation from tilt if we can */
         if (tilt_array == nullptr || nu->tilt_interp != nu->radius_interp) {
-          key_curve_position_weights(fac, t, nu->radius_interp);
+          key_curve_position_weights(fac, t, KeyInterpolationType(nu->radius_interp));
         }
         *radius_array = t[0] * pprev->radius + t[1] * prevbezt->radius + t[2] * bezt->radius +
                         t[3] * next->radius;
diff --git a/source/blender/blenkernel/intern/key.cc b/source/blender/blenkernel/intern/key.cc
index e047041b8d6..ec89d8583a9 100644
--- a/source/blender/blenkernel/intern/key.cc
+++ b/source/blender/blenkernel/intern/key.cc
@@ -338,116 +338,122 @@ void BKE_key_sort(Key *key)
 
 /**************** do the key ****************/
 
-void key_curve_position_weights(float t, float data[4], int type)
+void key_curve_position_weights(float t, float data[4], KeyInterpolationType type)
 {
   float t2, t3, fc;
 
-  if (type == KEY_LINEAR) {
-    data[0] = 0.0f;
-    data[1] = -t + 1.0f;
-    data[2] = t;
-    data[3] = 0.0f;
-  }
-  else if (type == KEY_CARDINAL) {
-    t2 = t * t;
-    t3 = t2 * t;
-    fc = 0.71f;
+  switch (type) {
+    case KEY_LINEAR:
+      data[0] = 0.0f;
+      data[1] = -t + 1.0f;
+      data[2] = t;
+      data[3] = 0.0f;
+      break;
+    case KEY_CARDINAL:
+      t2 = t * t;
+      t3 = t2 * t;
+      fc = 0.71f;
 
-    data[0] = -fc * t3 + 2.0f * fc * t2 - fc * t;
-    data[1] = (2.0f - fc) * t3 + (fc - 3.0f) * t2 + 1.0f;
-    data[2] = (fc - 2.0f) * t3 + (3.0f - 2.0f * fc) * t2 + fc * t;
-    data[3] = fc * t3 - fc * t2;
-  }
-  else if (type == KEY_BSPLINE) {
-    t2 = t * t;
-    t3 = t2 * t;
+      data[0] = -fc * t3 + 2.0f * fc * t2 - fc * t;
+      data[1] = (2.0f - fc) * t3 + (fc - 3.0f) * t2 + 1.0f;
+      data[2] = (fc - 2.0f) * t3 + (3.0f - 2.0f * fc) * t2 + fc * t;
+      data[3] = fc * t3 - fc * t2;
+      break;
+    case KEY_BSPLINE:
+      t2 = t * t;
+      t3 = t2 * t;
 
-    data[0] = -0.16666666f * t3 + 0.5f * t2 - 0.5f * t + 0.16666666f;
-    data[1] = 0.5f * t3 - t2 + 0.66666666f;
-    data[2] = -0.5f * t3 + 0.5f * t2 + 0.5f * t + 0.16666666f;
-    data[3] = 0.16666666f * t3;
-  }
-  else if (type == KEY_CATMULL_ROM) {
-    t2 = t * t;
-    t3 = t2 * t;
-    fc = 0.5f;
+      data[0] = -0.16666666f * t3 + 0.5f * t2 - 0.5f * t + 0.16666666f;
+      data[1] = 0.5f * t3 - t2 + 0.66666666f;
+      data[2] = -0.5f * t3 + 0.5f * t2 + 0.5f * t + 0.16666666f;
+      data[3] = 0.16666666f * t3;
+      break;
+    case KEY_CATMULL_ROM:
+      t2 = t * t;
+      t3 = t2 * t;
+      fc = 0.5f;
 
-    data[0] = -fc * t3 + 2.0f * fc * t2 - fc * t;
-    data[1] = (2.0f - fc) * t3 + (fc - 3.0f) * t2 + 1.0f;
-    data[2] = (fc - 2.0f) * t3 + (3.0f - 2.0f * fc) * t2 + fc * t;
-    data[3] = fc * t3 - fc * t2;
+      data[0] = -fc * t3 + 2.0f * fc * t2 - fc * t;
+      data[1] = (2.0f - fc) * t3 + (fc - 3.0f) * t2 + 1.0f;
+      data[2] = (fc - 2.0f) * t3 + (3.0f - 2.0f * fc) * t2 + fc * t;
+      data[3] = fc * t3 - fc * t2;
+      break;
   }
 }
 
-void key_curve_tangent_weights(float t, float data[4], int type)
+void key_curve_tangent_weights(float t, float data[4], KeyInterpolationType type)
 {
   float t2, fc;
 
-  if (type == KEY_LINEAR) {
-    data[0] = 0.0f;
-    data[1] = -1.0f;
-    data[2] = 1.0f;
-    data[3] = 0.0f;
-  }
-  else if (type == KEY_CARDINAL) {
-    t2 = t * t;
-    fc = 0.71f;
+  switch (type) {
+    case KEY_LINEAR:
+      data[0] = 0.0f;
+      data[1] = -1.0f;
+      data[2] = 1.0f;
+      data[3] = 0.0f;
+      break;
+    case KEY_CARDINAL:
+      t2 = t * t;
+      fc = 0.71f;
 
-    data[0] = -3.0f * fc * t2 + 4.0f * fc * t - fc;
-    data[1] = 3.0f * (2.0f - fc) * t2 + 2.0f * (fc - 3.0f) * t;
-    data[2] = 3.0f * (fc - 2.0f) * t2 + 2.0f * (3.0f - 2.0f * fc) * t + fc;
-    data[3] = 3.0f * fc * t2 - 2.0f * fc * t;
-  }
-  else if (type == KEY_BSPLINE) {
-    t2 = t * t;
+      data[0] = -3.0f * fc * t2 + 4.0f * fc * t - fc;
+      data[1] = 3.0f * (2.0f - fc) * t2 + 2.0f * (fc - 3.0f) * t;
+      data[2] = 3.0f * (fc - 2.0f) * t2 + 2.0f * (3.0f - 2.0f * fc) * t + fc;
+      data[3] = 3.0f * fc * t2 - 2.0f * fc * t;
+      break;
+    case KEY_BSPLINE:
+      t2 = t * t;
 
-    data[0] = -0.5f * t2 + t - 0.5f;
-    data[1] = 1.5f * t2 - t * 2.0f;
-    data[2] = -1.5f * t2 + t + 0.5f;
-    data[3] = 0.5f * t2;
-  }
-  else if (type == KEY_CATMULL_ROM) {
-    t2 = t * t;
-    fc = 0.5f;
+      data[0] = -0.5f * t2 + t - 0.5f;
+      data[1] = 1.5f * t2 - t * 2.0f;
+      data[2] = -1.5f * t2 + t + 0.5f;
+      data[3] = 0.5f * t2;
+      break;
+    case KEY_CATMULL_ROM:
+      t2 = t * t;
+      fc = 0.5f;
 
-    data[0] = -3.0f * fc * t2 + 4.0f * fc * t - fc;
-    data[1] = 3.0f * (2.0f - fc) * t2 + 2.0f * (fc - 3.0f) * t;
-    data[2] = 3.0f * (fc - 2.0f) * t2 + 2.0f * (3.0f - 2.0f * fc) * t + fc;
-    data[3] = 3.0f * fc * t2 - 2.0f * fc * t;
+      data[0] = -3.0f * fc * t2 + 4.0f * fc * t - fc;
+      data[1] = 3.0f * (2.0f - fc) * t2 + 2.0f * (fc - 3.0f) * t;
+      data[2] = 3.0f * (fc - 2.0f) * t2 + 2.0f * (3.0f - 2.0f * fc) * t + fc;
+      data[3] = 3.0f * fc * t2 - 2.0f * fc * t;
+      break;
   }
 }
 
-void key_curve_normal_weights(float t, float data[4], int type)
+void key_curve_normal_weights(float t, float data[4], KeyInterpolationType type)
 {
   float fc;
 
-  if (type == KEY_LINEAR) {
-    data[0] = 0.0f;
-    data[1] = 0.0f;
-    data[2] = 0.0f;
-    data[3] = 0.0f;
-  }
-  else if (type == KEY_CARDINAL) {
-    fc = 0.71f;
+  switch (type) {
+    case KEY_LINEAR:
+      data[0] = 0.0f;
+      data[1] = 0.0f;
+      data[2] = 0.0f;
+      data[3] = 0.0f;
+      break;
+    case KEY_CARDINAL:
+      fc = 0.71f;
 
-    data[0] = -6.0f * fc * t + 4.0f * fc;
-    data[1] = 6.0f * (2.0f - fc) * t + 2.0f * (fc - 3.0f);
-    data[2] = 6.0f * (fc - 2.0f) * t + 2.0f * (3.0f - 2.0f * fc);
-    data[3] = 6.0f * fc * t - 2.0f * fc;
-  }
-  else if (type == KEY_BSPLINE) {
-    data[0] = -1.0f * t + 1.0f;
-    data[1] = 3.0f * t - 2.0f;
-    data[2] = -3.0f * t + 1.0f;
-    data[3] = 1.0f * t;
-  }
-  else if (type == KEY_CATMULL_ROM) {
-    fc = 0.5f;
+      data[0] = -6.0f * fc * t + 4.0f * fc;
+      data[1] = 6.0f * (2.0f - fc) * t + 2.0f * (fc - 3.0f);
+      data[2] = 6.0f * (fc - 2.0f) * t + 2.0f * (3.0f - 2.0f * fc);
+      data[3] = 6.0f * fc * t - 2.0f * fc;
+      break;
+    case KEY_BSPLINE:
+      data[0] = -1.0f * t + 1.0f;
+      data[1] = 3.0f * t - 2.0f;
+      data[2] = -3.0f * t + 1.0f;
+      data[3] = 1.0f * t;
+      break;
+    case KEY_CATMULL_ROM:
+      fc = 0.5f;
 
-    data[0] = -6.0f * fc * t + 4.0f * fc;
-    data[1] = 6.0f * (2.0f - fc) * t + 2.0f * (fc - 3.0f);
-    data[2] = 6.0f * (fc - 2.0f) * t + 2.0f * (3.0f - 2.0f * fc);
-    data[3] = 6.0f * fc * t - 2.0f * fc;
+      data[0] = -6.0f * fc * t + 4.0f * fc;
+      data[1] = 6.0f * (2.0f - fc) * t + 2.0f * (fc - 3.0f);
+      data[2] = 6.0f * (fc - 2.0f) * t + 2.0f * (3.0f - 2.0f * fc);
+      data[3] = 6.0f * fc * t - 2.0f * fc;
+      break;
   }
 }
 
@@ -584,11 +590,11 @@ static int setkeys(float fac, ListBase *lb, KeyBlock *k[], float t[4], int cycl)
   }
 
   /* interpolation */
-  key_curve_position_weights(d, t, k[1]->type);
+  key_curve_position_weights(d, t, KeyInterpolationType(k[1]->type));
 
   if (k[1]->type != k[2]->type) {
     float t_other[4];
-    key_curve_position_weights(d, t_other, k[2]->type);
+    key_curve_position_weights(d, t_other, KeyInterpolationType(k[2]->type));
     interp_v4_v4v4(t, t, t_other, d);
   }
 
diff --git a/source/blender/blenkernel/intern/lattice_deform.cc b/source/blender/blenkernel/intern/lattice_deform.cc
index 19caa6f8e7c..b42813b86da 100644
--- a/source/blender/blenkernel/intern/lattice_deform.cc
+++ b/source/blender/blenkernel/intern/lattice_deform.cc
@@ -167,7 +167,7 @@ void BKE_lattice_deform_data_eval_co(LatticeDeformData *lattice_deform_data,
     u = (vec[0] - lt->fu) / lt->du;
     ui = int(floor(u));
     u -= ui;
-    key_curve_position_weights(u, tu, lt->typeu);
+    key_curve_position_weights(u, tu, KeyInterpolationType(lt->typeu));
   }
   else {
     tu[0] = tu[2] = tu[3] = 0.0;
@@ -179,7 +179,7 @@ void BKE_lattice_deform_data_eval_co(LatticeDeformData *lattice_deform_data,
     v = (vec[1] - lt->fv) / lt->dv;
     vi = int(floor(v));
     v -= vi;
-    key_curve_position_weights(v, tv, lt->typev);
+    key_curve_position_weights(v, tv, KeyInterpolationType(lt->typev));
   }
   else {
     tv[0] = tv[2] = tv[3] = 0.0;
@@ -191,7 +191,7 @@ void BKE_lattice_deform_data_eval_co(LatticeDeformData *lattice_deform_data,
     w = (vec[2] - lt->fw) / lt->dw;
     wi = int(floor(w));
     w -= wi;
-    key_curve_position_weights(w, tw, lt->typew);
+    key_curve_position_weights(w, tw, KeyInterpolationType(lt->typew));
   }
   else {
     tw[0] = tw[2] = tw[3] = 0.0;
diff --git a/source/blender/blenkernel/intern/particle.cc b/source/blender/blenkernel/intern/particle.cc
index c7c1b0cfcf0..7cb1c870f26 100644
--- a/source/blender/blenkernel/intern/particle.cc
+++ b/source/blender/blenkernel/intern/particle.cc
@@ -1145,7 +1145,7 @@ void psys_interpolate_particle(
     interp_cubic_v3(result->co, result->vel, keys[1].co, keys[1].vel, keys[2].co, keys[2].vel, dt);
   }
   else {
-    key_curve_position_weights(dt, t, type);
+    key_curve_position_weights(dt, t, KeyInterpolationType(type));
 
     interp_v3_v3v3v3v3(result->co, keys[0].co, keys[1].co, keys[2].co, keys[3].co, t);
 
@@ -1153,12 +1153,12 @@ void psys_interpolate_particle(
       float temp[3];
 
       if (dt > 0.999f) {
-        key_curve_position_weights(dt - 0.001f, t, type);
+        key_curve_position_weights(dt - 0.001f, t, KeyInterpolationType(type));
         interp_v3_v3v3v3v3(temp, keys[0].co, keys[1].co, keys[2].co, keys[3].co, t);
         sub_v3_v3v3(result->vel, result->co, temp);
       }
       else {
-        key_curve_position_weights(dt + 0.001f, t, type);
+        key_curve_position_weights(dt + 0.001f, t, KeyInterpolationType(type));
         interp_v3_v3v3v3v3(temp, keys[0].co, keys[1].co, keys[2].co, keys[3].co, t);
         sub_v3_v3v3(result->vel, temp, result->co);
       }
diff --git a/source/blender/makesdna/DNA_key_types.h b/source/blender/makesdna/DNA_key_types.h
index 4004238fe7c..bdf35ba6313 100644
--- a/source/blender/makesdna/DNA_key_types.h
+++ b/source/blender/makesdna/DNA_key_types.h
@@ -18,39 +18,45 @@
 struct AnimData;
 struct Ipo;
 
+/**
+ * The struct that holds the data for an individual Shape Key. Depending on which object owns the
+ * `Key`, the contained data type can vary (see `void *data;`).
+ */
 typedef struct KeyBlock {
   struct KeyBlock *next, *prev;
 
   /**
-   * point in time   (Key->type == KEY_NORMAL) only,
-   * for historic reasons this is relative to (Key->ctime / 100),
+   * A point in time used in case of `(Key::type == KEY_NORMAL)` only,
+   * for historic reasons this is relative to (Key::ctime / 100),
    * so this value increments by 0.1f per frame.
    */
   float pos;
-  /** influence (typically [0 - 1] but can be more), `(Key->type == KEY_RELATIVE)` only. */
+  /** Influence (typically [0 - 1] but can be more), `(Key::type == KEY_RELATIVE)` only. */
   float curval;
 
-  /** Interpolation type `(Key->type == KEY_NORMAL)` only. */
+  /** Interpolation type. Used for `(Key::type == KEY_NORMAL)` only (KeyInterpolationType). */
   short type;
   char _pad1[2];
 
-  /** relative == 0 means first key is reference, otherwise the index of Key->blocks */
+  /** `relative == 0` means first key is reference, otherwise the index of Key::blocks. */
   short relative;
+  /* KeyBlockFlag */
   short flag;
 
-  /** total number if items in the keyblock (compare with mesh/curve verts to check we match) */
+  /** Total number of items in the keyblock (compare with mesh/curve verts to check we match). */
   int totelem;
-  /** for meshes only, match the unique number with the customdata layer */
+  /** For meshes only, match the unique number with the customdata layer. */
   int uid;
 
-  /** array of shape key values, size is `(Key->elemsize * KeyBlock->totelem)` */
+  /** Array of shape key values, size is `(Key::elemsize * KeyBlock->totelem)`.
+   * E.g. meshes use float3. */
   void *data;
-  /** MAX_NAME (unique name, user assigned) */
+  /** MAX_NAME (unique name, user assigned). */
   char name[64];
-  /** MAX_VGROUP_NAME (optional vertex group), array gets allocated into 'weights' when set */
+  /** MAX_VGROUP_NAME (optional vertex group), array gets allocated into 'weights' when set. */
   char vgroup[64];
 
-  /** ranges, for RNA and UI only to clamp 'curval' */
+  /** Ranges, for RNA and UI only to clamp 'curval'. */
   float slidermin;
   float slidermax;
 
@@ -67,9 +73,9 @@ typedef struct Key {
   struct AnimData *adt;
 
   /**
-   * commonly called 'Basis', `(Key->type == KEY_RELATIVE)` only.
-   * Looks like this is  _always_ 'key->block.first',
-   * perhaps later on it could be defined as some other KeyBlock - campbell
+   * Commonly called 'Basis', `(Key::type == KEY_RELATIVE)` only.
+   * Looks like this is _always_ 'key->block.first',
+   * perhaps later on it could be defined as some other KeyBlock - campbell.
    */
   KeyBlock *refkey;
 
@@ -82,21 +88,22 @@ typedef struct Key {
   int elemsize;
   char _pad[4];
 
-  /** list of KeyBlock's */
+  /** A list of KeyBlock's. */
   ListBase block;
-  /** old animation system, deprecated for 2.5 */
+  /** Old animation system, deprecated for 2.5. */
   struct Ipo *ipo DNA_DEPRECATED;
 
   ID *from;
 
-  /** (totkey == BLI_listbase_count(&key->block)) */
+  /** (totkey == BLI_listbase_count(&key->block)). */
   int totkey;
+  /* ShapekeyContainerFlag */
   short flag;
-  /** absolute or relative shape key */
+  /** Absolute or relative shape key (ShapekeyContainerType). */
   char type;
   char _pad2;
 
-  /** Only used when (Key->type == KEY_NORMAL), this value is used as a time slider,
+  /** Only used when (Key::type == KEY_NORMAL), this value is used as a time slider,
    * rather than using the scene's time, this value can be animated to give greater control */
   float ctime;
 
@@ -109,35 +116,35 @@ typedef struct Key {
 
 /* **************** KEY ********************* */
 
-/* Key->type: KeyBlocks are interpreted as... */
-enum {
-  /* Sequential positions over time (using KeyBlock->pos and Key->ctime) */
+/* Key::type: KeyBlocks are interpreted as... */
+typedef enum ShapekeyContainerType {
+  /* Sequential positions over time (using KeyBlock::pos and Key::ctime) */
   KEY_NORMAL = 0,
 
   /* States to blend between (default) */
   KEY_RELATIVE = 1,
-};
+} ShapekeyContainerType;
 
-/* Key->flag */
-enum {
+/* Key::flag */
+typedef enum ShapekeyContainerFlag {
   KEY_DS_EXPAND = 1,
-};
+} ShapekeyContainerFlag;
 
-/* KeyBlock->type */
-enum {
+/* The obvious name would be `KeyBlockType` but this enum is actually used in places outside of
+ * Shape Keys (NURBS, particles, etc.). */
+typedef enum KeyInterpolationType {
   KEY_LINEAR = 0,
   KEY_CARDINAL = 1,
   KEY_BSPLINE = 2,
   KEY_CATMULL_ROM = 3,
-};
+} KeyInterpolationType;
 
-/* KeyBlock->flag */
-enum {
+typedef enum KeyBlockFlag {
   KEYBLOCK_MUTE = (1 << 0),
   KEYBLOCK_SEL = (1 << 1),
   KEYBLOCK_LOCKED = (1 << 2),
   KEYBLOCK_LOCKED_SHAPE = (1 << 3),
-};
+} KeyBlockFlag;
 
 #define KEYELEM_FLOAT_LEN_COORD 3
 
diff --git a/source/blender/makesdna/DNA_lattice_types.h b/source/blender/makesdna/DNA_lattice_types.h
index ecfbc4e5de9..a86db306196 100644
--- a/source/blender/makesdna/DNA_lattice_types.h
+++ b/source/blender/makesdna/DNA_lattice_types.h
@@ -46,6 +46,7 @@ typedef struct Lattice {
   short pntsu, pntsv, pntsw, flag;
   short opntsu, opntsv, opntsw;
   char _pad2[3];
+  /* KeyInterpolationType */
   char typeu, typev, typew;
   /** Active element index, unset with LT_ACTBP_NONE. */
   int actbp;