`R_PAUSE_MENU_MODE` -> `R_PAUSE_BG_PRERENDER_STATE` and docs (#1368)

* `R_PAUSE_MENU_MODE` -> `R_PAUSE_BG_PRERENDER_STATE` and document values and usage

* `SREG(33)` -> `R_GRAPH_TASKSET00_FLAGS`

* format

* `PAUSE_BG_PRERENDER_DRAW` -> `PAUSE_BG_PRERENDER_SETUP`

* `PAUSE_BG_PRERENDER_FILTER` -> `PAUSE_BG_PRERENDER_PROCESS`

* DList -> display list

6 files changed, 38 insertions, 28 deletions

diff --git a/src/code/game.c b/src/code/game.c
index ae22e6ab3..9f3bc91bc 100644
--- a/src/code/game.c
+++ b/src/code/game.c
@@ -319,7 +319,7 @@ void GameState_Update(GameState* gameState) {
         }
     }
 
-    if (R_PAUSE_MENU_MODE != 2u) {
+    if (R_PAUSE_BG_PRERENDER_STATE != (u32)PAUSE_BG_PRERENDER_PROCESS) {
         GameState_Draw(gameState, gfxCtx);
         func_800C49F4(gfxCtx);
     }
diff --git a/src/code/graph.c b/src/code/graph.c
index 1c9093dc9..e5309966c 100644
--- a/src/code/graph.c
+++ b/src/code/graph.c
@@ -242,8 +242,8 @@ void Graph_TaskSet00(GraphicsContext* gfxCtx) {
 
     scTask->next = NULL;
     scTask->flags = OS_SC_NEEDS_RSP | OS_SC_NEEDS_RDP | OS_SC_SWAPBUFFER | OS_SC_LAST_TASK;
-    if (SREG(33) & 1) {
-        SREG(33) &= ~1;
+    if (R_GRAPH_TASKSET00_FLAGS & 1) {
+        R_GRAPH_TASKSET00_FLAGS &= ~1;
         scTask->flags &= ~OS_SC_SWAPBUFFER;
         gfxCtx->fbIdx--;
     }
diff --git a/src/code/z_kaleido_scope_call.c b/src/code/z_kaleido_scope_call.c
index b9c116ff1..ced5b5203 100644
--- a/src/code/z_kaleido_scope_call.c
+++ b/src/code/z_kaleido_scope_call.c
@@ -61,7 +61,7 @@ void KaleidoScopeCall_Update(PlayState* play) {
             if (Letterbox_GetSize() == 0) {
                 R_HREG_MODE = HREG_MODE_UCODE_DISAS;
                 R_UCODE_DISAS_LOG_MODE = 3;
-                R_PAUSE_MENU_MODE = 1;
+                R_PAUSE_BG_PRERENDER_STATE = PAUSE_BG_PRERENDER_SETUP;
                 pauseCtx->unk_1E4 = 0;
                 pauseCtx->unk_1EC = 0;
                 pauseCtx->state = (pauseCtx->state & 0xFFFF) + 1;
@@ -69,14 +69,14 @@ void KaleidoScopeCall_Update(PlayState* play) {
         } else if (pauseCtx->state == 8) {
             R_HREG_MODE = HREG_MODE_UCODE_DISAS;
             R_UCODE_DISAS_LOG_MODE = 3;
-            R_PAUSE_MENU_MODE = 1;
+            R_PAUSE_BG_PRERENDER_STATE = PAUSE_BG_PRERENDER_SETUP;
             pauseCtx->unk_1E4 = 0;
             pauseCtx->unk_1EC = 0;
             pauseCtx->state = (pauseCtx->state & 0xFFFF) + 1;
         } else if ((pauseCtx->state == 2) || (pauseCtx->state == 9)) {
-            osSyncPrintf("PR_KAREIDOSCOPE_MODE=%d\n", R_PAUSE_MENU_MODE);
+            osSyncPrintf("PR_KAREIDOSCOPE_MODE=%d\n", R_PAUSE_BG_PRERENDER_STATE);
 
-            if (R_PAUSE_MENU_MODE >= 3) {
+            if (R_PAUSE_BG_PRERENDER_STATE >= PAUSE_BG_PRERENDER_DONE) {
                 pauseCtx->state++;
             }
         } else if (pauseCtx->state != 0) {
@@ -118,7 +118,7 @@ void KaleidoScopeCall_Update(PlayState* play) {
 void KaleidoScopeCall_Draw(PlayState* play) {
     KaleidoMgrOverlay* kaleidoScopeOvl = &gKaleidoMgrOverlayTable[KALEIDO_OVL_KALEIDO_SCOPE];
 
-    if (R_PAUSE_MENU_MODE >= 3) {
+    if (R_PAUSE_BG_PRERENDER_STATE >= PAUSE_BG_PRERENDER_DONE) {
         if (((play->pauseCtx.state >= 4) && (play->pauseCtx.state <= 7)) ||
             ((play->pauseCtx.state >= 11) && (play->pauseCtx.state <= 18))) {
             if (gKaleidoMgrCurOvl == kaleidoScopeOvl) {
diff --git a/src/code/z_parameter.c b/src/code/z_parameter.c
index b63702ec3..b8e7a0a8d 100644
--- a/src/code/z_parameter.c
+++ b/src/code/z_parameter.c
@@ -3238,7 +3238,8 @@ void Interface_Draw(PlayState* play) {
         Magic_DrawMeter(play);
         Minimap_Draw(play);
 
-        if ((R_PAUSE_MENU_MODE != 2) && (R_PAUSE_MENU_MODE != 3)) {
+        if ((R_PAUSE_BG_PRERENDER_STATE != PAUSE_BG_PRERENDER_PROCESS) &&
+            (R_PAUSE_BG_PRERENDER_STATE != PAUSE_BG_PRERENDER_DONE)) {
             func_8002C124(&play->actorCtx.targetCtx, play); // Draw Z-Target
         }
 
diff --git a/src/code/z_play.c b/src/code/z_play.c
index 4f8284cfd..9a3fb3204 100644
--- a/src/code/z_play.c
+++ b/src/code/z_play.c
@@ -179,7 +179,7 @@ void Play_Destroy(GameState* thisx) {
     this->state.gfxCtx->callbackParam = NULL;
 
     SREG(91) = 0;
-    R_PAUSE_MENU_MODE = 0;
+    R_PAUSE_BG_PRERENDER_STATE = PAUSE_BG_PRERENDER_OFF;
 
     PreRender_Destroy(&this->pauseBgPreRender);
     Effect_DeleteAll(this);
@@ -357,7 +357,7 @@ void Play_Init(GameState* thisx) {
     }
 
     SREG(91) = -1;
-    R_PAUSE_MENU_MODE = 0;
+    R_PAUSE_BG_PRERENDER_STATE = PAUSE_BG_PRERENDER_OFF;
     PreRender_Init(&this->pauseBgPreRender);
     PreRender_SetValuesSave(&this->pauseBgPreRender, SCREEN_WIDTH, SCREEN_HEIGHT, NULL, NULL, NULL);
     PreRender_SetValues(&this->pauseBgPreRender, SCREEN_WIDTH, SCREEN_HEIGHT, NULL, NULL);
@@ -1115,19 +1115,25 @@ void Play_Draw(PlayState* this) {
         } else {
             PreRender_SetValues(&this->pauseBgPreRender, SCREEN_WIDTH, SCREEN_HEIGHT, gfxCtx->curFrameBuffer, gZBuffer);
 
-            if (R_PAUSE_MENU_MODE == 2) {
+            if (R_PAUSE_BG_PRERENDER_STATE == PAUSE_BG_PRERENDER_PROCESS) {
+                // Wait for the previous frame's display list to be processed,
+                // so that `pauseBgPreRender.fbufSave` and `pauseBgPreRender.cvgSave` are filled with the appropriate
+                // content and can be used by `PreRender_ApplyFilters` below.
                 Sched_FlushTaskQueue();
+
                 PreRender_ApplyFilters(&this->pauseBgPreRender);
-                R_PAUSE_MENU_MODE = 3;
-            } else if (R_PAUSE_MENU_MODE >= 4) {
-                R_PAUSE_MENU_MODE = 0;
+
+                R_PAUSE_BG_PRERENDER_STATE = PAUSE_BG_PRERENDER_DONE;
+            } else if (R_PAUSE_BG_PRERENDER_STATE >= PAUSE_BG_PRERENDER_MAX) {
+                R_PAUSE_BG_PRERENDER_STATE = PAUSE_BG_PRERENDER_OFF;
             }
 
-            if (R_PAUSE_MENU_MODE == 3) {
-                Gfx* sp84 = POLY_OPA_DISP;
+            if (R_PAUSE_BG_PRERENDER_STATE == PAUSE_BG_PRERENDER_DONE) {
+                Gfx* gfxP = POLY_OPA_DISP;
+
+                PreRender_RestoreFramebuffer(&this->pauseBgPreRender, &gfxP);
+                POLY_OPA_DISP = gfxP;
 
-                PreRender_RestoreFramebuffer(&this->pauseBgPreRender, &sp84);
-                POLY_OPA_DISP = sp84;
                 goto Play_Draw_DrawOverlayElements;
             } else {
                 s32 roomDrawFlags;
@@ -1238,22 +1244,25 @@ void Play_Draw(PlayState* this) {
                     DebugDisplay_DrawObjects(this);
                 }
 
-                if ((R_PAUSE_MENU_MODE == 1) || (gTrnsnUnkState == 1)) {
-                    Gfx* sp70 = OVERLAY_DISP;
+                if ((R_PAUSE_BG_PRERENDER_STATE == PAUSE_BG_PRERENDER_SETUP) || (gTrnsnUnkState == 1)) {
+                    Gfx* gfxP = OVERLAY_DISP;
 
+                    // Copy the frame buffer contents at this point in the display list to the zbuffer
+                    // The zbuffer must then stay untouched until unpausing
                     this->pauseBgPreRender.fbuf = gfxCtx->curFrameBuffer;
                     this->pauseBgPreRender.fbufSave = (u16*)gZBuffer;
-                    PreRender_SaveFramebuffer(&this->pauseBgPreRender, &sp70);
-                    if (R_PAUSE_MENU_MODE == 1) {
+                    PreRender_SaveFramebuffer(&this->pauseBgPreRender, &gfxP);
+                    if (R_PAUSE_BG_PRERENDER_STATE == PAUSE_BG_PRERENDER_SETUP) {
                         this->pauseBgPreRender.cvgSave = (u8*)gfxCtx->curFrameBuffer;
-                        PreRender_DrawCoverage(&this->pauseBgPreRender, &sp70);
-                        R_PAUSE_MENU_MODE = 2;
+                        PreRender_DrawCoverage(&this->pauseBgPreRender, &gfxP);
+
+                        R_PAUSE_BG_PRERENDER_STATE = PAUSE_BG_PRERENDER_PROCESS;
                     } else {
                         gTrnsnUnkState = 2;
                     }
-                    OVERLAY_DISP = sp70;
+                    OVERLAY_DISP = gfxP;
                     this->unk_121C7 = 2;
-                    SREG(33) |= 1;
+                    R_GRAPH_TASKSET00_FLAGS |= 1;
                 } else {
                 Play_Draw_DrawOverlayElements:
                     if ((R_HREG_MODE != HREG_MODE_PLAY) || R_PLAY_DRAW_OVERLAY_ELEMENTS) {
diff --git a/src/code/z_rcp.c b/src/code/z_rcp.c
index 8b8c6d9be..7b9328459 100644
--- a/src/code/z_rcp.c
+++ b/src/code/z_rcp.c
@@ -1469,7 +1469,7 @@ void Gfx_SetupFrame(GraphicsContext* gfxCtx, u8 r, u8 g, u8 b) {
     gDPSetDepthImage(POLY_XLU_DISP++, gZBuffer);
     gDPSetDepthImage(OVERLAY_DISP++, gZBuffer);
 
-    if ((R_PAUSE_MENU_MODE < 2) && (gTrnsnUnkState < 2)) {
+    if ((R_PAUSE_BG_PRERENDER_STATE <= PAUSE_BG_PRERENDER_SETUP) && (gTrnsnUnkState < 2)) {
         s32 letterboxSize = Letterbox_GetSize();
 
         if (R_HREG_MODE == HREG_MODE_SETUP_FRAME) {