More documentation for sched.c (#1219)

* More documentation for sched.c

* VI retrace -> vertical retrace, attempt to clarify comment in viconfig

* Further review changes, fix inconsistent capitalization of PreNMI (PRENMI -> PreNMI)

* Fix typo

Co-authored-by: engineer124 <47598039+engineer124@users.noreply.github.com>

* Change TaskSwapBuffer, change comment on OS_SC_DRAM_DLIST to unimplemented

* Rename SchedContext/gSchedContext to Scheduler/gScheduler

* Comments fixes

Co-authored-by: Dragorn421 <Dragorn421@users.noreply.github.com>

* Format

Co-authored-by: engineer124 <47598039+engineer124@users.noreply.github.com>
Co-authored-by: Dragorn421 <Dragorn421@users.noreply.github.com>

2 files changed, 15 insertions, 10 deletions

diff --git a/src/boot/idle.c b/src/boot/idle.c
index f4e3715d7..8e72b8256 100644
--- a/src/boot/idle.c
+++ b/src/boot/idle.c
@@ -10,7 +10,7 @@ OSViMode gViConfigMode;
 u8 D_80013960;
 
 s8 D_80009430 = 1;
-vu8 gViConfigUseDefault = 1;
+vu8 gViConfigBlack = true;
 u8 gViConfigAdditionalScanLines = 0;
 u32 gViConfigFeatures = OS_VI_DITHER_FILTER_ON | OS_VI_GAMMA_OFF;
 f32 gViConfigXScale = 1.0;
@@ -75,8 +75,8 @@ void Idle_ThreadEntry(void* arg) {
 
     D_80009430 = 1;
     osViSetMode(&gViConfigMode);
-    ViConfig_UpdateVi(1);
-    osViBlack(1);
+    ViConfig_UpdateVi(true);
+    osViBlack(true);
     osViSwapBuffer(0x803DA80); //! @bug Invalid vram address (probably intended to be 0x803DA800)
     osCreatePiManager(OS_PRIORITY_PIMGR, &gPiMgrCmdQueue, sPiMgrCmdBuff, ARRAY_COUNT(sPiMgrCmdBuff));
     StackCheck_Init(&sMainStackInfo, sMainStack, STACK_TOP(sMainStack), 0, 0x400, "main");
diff --git a/src/boot/viconfig.c b/src/boot/viconfig.c
index 4c6830c99..38942097f 100644
--- a/src/boot/viconfig.c
+++ b/src/boot/viconfig.c
@@ -2,16 +2,21 @@
 #include "vt.h"
 
 // this should probably go elsewhere but right now viconfig.o is the only object between idle and z_std_dma
-OSPiHandle* gCartHandle = 0;
+OSPiHandle* gCartHandle = NULL;
+
+void ViConfig_UpdateVi(u32 black) {
+    if (black) {
+        // Black the screen on next call to ViConfig_UpdateBlack, skip most VI configuration
 
-void ViConfig_UpdateVi(u32 mode) {
-    if (mode != 0) {
         osSyncPrintf(VT_COL(YELLOW, BLACK) "osViSetYScale1(%f);\n" VT_RST, 1.0f);
 
         if (osTvType == OS_TV_PAL) {
             osViSetMode(&osViModePalLan1);
         }
 
+        // Reset the VI y scale. The VI y scale is different between NTSC (1.0) and PAL (0.833)
+        // and should be reset to 1.0 during PreNMI to ensure there are no issues when restarting.
+        // (see section 30.4.3 VI Processing with PreNMI Events in the N64 Programming Manual)
         osViSetYScale(1.0f);
     } else {
         osViSetMode(&gViConfigMode);
@@ -34,13 +39,13 @@ void ViConfig_UpdateVi(u32 mode) {
         }
     }
 
-    gViConfigUseDefault = mode;
+    gViConfigBlack = black;
 }
 
 void ViConfig_UpdateBlack(void) {
-    if (gViConfigUseDefault != 0) {
-        osViBlack(1);
+    if (gViConfigBlack) {
+        osViBlack(true);
     } else {
-        osViBlack(0);
+        osViBlack(false);
     }
 }