Document Player's Face and z_actor FaceChange functions (#1928)

* create some enums

* gonna try struct instead of array

* struct works. add docs too

* inline function comments

* fix function comment

* name faces, move enums

* rename textures

* outnames

* remove comments

* change comment slightly

* fixup face comments

* review

* offset comments

* add and use PLAYER_FACE_MAX

* typo

* more comment on blinkDuration

* another change to the comment

1 files changed, 50 insertions, 19 deletions

diff --git a/src/code/z_actor.c b/src/code/z_actor.c
index d9b7f579c..128fa94d8 100644
--- a/src/code/z_actor.c
+++ b/src/code/z_actor.c
@@ -3189,33 +3189,64 @@ void Enemy_StartFinishingBlow(PlayState* play, Actor* actor) {
     SfxSource_PlaySfxAtFixedWorldPos(play, &actor->world.pos, 20, NA_SE_EN_LAST_DAMAGE);
 }
 
-s16 func_80032CB4(s16* arg0, s16 arg1, s16 arg2, s16 arg3) {
-    if (DECR(arg0[1]) == 0) {
-        arg0[1] = Rand_S16Offset(arg1, arg2);
-    }
-
-    if ((arg0[1] - arg3) > 0) {
-        arg0[0] = 0;
-    } else if (((arg0[1] - arg3) > -2) || (arg0[1] < 2)) {
-        arg0[0] = 1;
+/**
+ * Updates `FaceChange` data for a blinking pattern.
+ * This system expects that the actor using the system has defined 3 faces in this exact order:
+ * "eyes open", "eyes half open", "eyes closed".
+ *
+ * @param faceChange  pointer to an actor's faceChange data
+ * @param blinkIntervalBase  The base number of frames between blinks
+ * @param blinkIntervalRandRange  The range for a random number of frames that can be added to `blinkIntervalBase`
+ * @param blinkDuration  The number of frames it takes for a single blink to occur
+ */
+s16 FaceChange_UpdateBlinking(FaceChange* faceChange, s16 blinkIntervalBase, s16 blinkIntervalRandRange,
+                              s16 blinkDuration) {
+    if (DECR(faceChange->timer) == 0) {
+        faceChange->timer = Rand_S16Offset(blinkIntervalBase, blinkIntervalRandRange);
+    }
+
+    if ((faceChange->timer - blinkDuration) > 0) {
+        // `timer - duration` is positive so this is the default state: "eyes open" face
+        faceChange->face = 0;
+    } else if (((faceChange->timer - blinkDuration) > -2) || (faceChange->timer < 2)) {
+        // This condition aims to catch both cases where the "eyes half open" face is needed.
+        // Note that the comparison assumes the duration of the "eyes half open" phase is 2 frames, irrespective of the
+        // value of `blinkDuration`. The duration for the "eyes closed" phase is `blinkDuration - 4`.
+        // For Player's use case `blinkDuration` is 6, so the "eyes closed" phase happens to have
+        // the same duration as each "eyes half open" phase.
+        faceChange->face = 1;
     } else {
-        arg0[0] = 2;
+        // If both conditions above fail, the only possibility left is the "eyes closed" face
+        faceChange->face = 2;
     }
 
-    return arg0[0];
+    return faceChange->face;
 }
 
-s16 func_80032D60(s16* arg0, s16 arg1, s16 arg2, s16 arg3) {
-    if (DECR(arg0[1]) == 0) {
-        arg0[1] = Rand_S16Offset(arg1, arg2);
-        arg0[0]++;
-
-        if ((arg0[0] % 3) == 0) {
-            arg0[0] = (s32)(Rand_ZeroOne() * arg3) * 3;
+/**
+ * Updates `FaceChange` data for randomly selected face sets.
+ * Each set contains 3 faces. After the timer runs out, the next face in the set is used.
+ * After the third face in a set is used, a new face set is randomly chosen.
+ *
+ * @param faceChange  pointer to an actor's faceChange data
+ * @param changeTimerBase  The base number of frames between each face change
+ * @param changeTimerRandRange  The range for a random number of frames that can be added to `changeTimerBase`
+ * @param faceSetRange  The max number of face sets that will be chosen from
+ */
+s16 FaceChange_UpdateRandomSet(FaceChange* faceChange, s16 changeTimerBase, s16 changeTimerRandRange,
+                               s16 faceSetRange) {
+    if (DECR(faceChange->timer) == 0) {
+        faceChange->timer = Rand_S16Offset(changeTimerBase, changeTimerRandRange);
+        faceChange->face++;
+
+        if ((faceChange->face % 3) == 0) {
+            // Randomly chose a "set number", then multiply by 3 because each set has 3 faces.
+            // This will use the first face in the newly chosen set.
+            faceChange->face = (s32)(Rand_ZeroOne() * faceSetRange) * 3;
         }
     }
 
-    return arg0[0];
+    return faceChange->face;
 }
 
 void BodyBreak_Alloc(BodyBreak* bodyBreak, s32 count, PlayState* play) {