From 9edf75b646e607177929307714acb725d33f22c1 Mon Sep 17 00:00:00 2001
From: Keith Leonardo <kleonardo52@gmail.com>
Date: Mon, 16 Oct 2023 00:14:25 +1100
Subject: [PATCH] Only allow writes to the PPU palette when rendering is
 disabled

---
 src/cpu_bus.c | 6 +++---
 src/io.c      | 4 ++--
 2 files changed, 5 insertions(+), 5 deletions(-)

diff --git a/src/cpu_bus.c b/src/cpu_bus.c
index 7ca8099..2157e09 100644
--- a/src/cpu_bus.c
+++ b/src/cpu_bus.c
@@ -135,7 +135,7 @@ unsigned char read_cpu_bus(cpu_bus_t *bus, address_t address) {
 
         // Read from OAMDATA (overwrite result with value from primary OAM)
         if (ptr == &bus->ppu->oam_data) {
-            result = bus->ppu->primary_oam[bus->ppu->oam_addr];
+            result = read_primary_oam_ppu(bus->ppu, bus->ppu->oam_addr);
             if ((bus->ppu->oam_addr % 4) == 2) {
                 result &= 0xE3;
             }
@@ -202,7 +202,7 @@ void write_cpu_bus(cpu_bus_t *bus, address_t address, unsigned char value) {
         // Write to OAMDATA
         if (ptr == &bus->ppu->oam_data) {
             if (is_rendering_ppu(bus->ppu)) {
-                bus->ppu->oam_addr += 0x04;
+                bus->ppu->oam_addr += 0x04; // Bump high 6 bits
             } else {
                 bus->ppu->primary_oam[bus->ppu->oam_addr++] = value;
             }
@@ -245,7 +245,7 @@ void write_cpu_bus(cpu_bus_t *bus, address_t address, unsigned char value) {
 
         // Write to PPUDATA
         if (ptr == &bus->ppu->data) {
-            if (bus->ppu->v >= PPU_MAP_PALETTE) {
+            if (bus->ppu->v >= PPU_MAP_PALETTE && !is_rendering_ppu(bus->ppu)) {
                 address_t palette_addr = bus->ppu->v & 0x1F;
                 write_palette_ppu(bus->ppu, palette_addr, value);
             } else {
diff --git a/src/io.c b/src/io.c
index 7720215..19c564b 100644
--- a/src/io.c
+++ b/src/io.c
@@ -56,8 +56,8 @@ void debug_io(io_t *io, emulator_t *emu) {
                 unsigned char pixel = ((plane0 >> (7 - x)) & 1) |
                                       (((plane1 >> (7 - x)) & 1) << 1);
                 vec2_t position = {
-                    (i % 16) * 8 + x,
-                    (unsigned)(i / 16) * 8 + y,
+                    (i & 15) * 8 + x,
+                    (unsigned)(i >> 4) * 8 + y,
                 };
                 color_t color = {0, 0, 0};
                 switch (pixel) {