Merge branch 'master' into rateless_apu

Core/display.c

@@ -144,10 +144,7 @@ static uint32_t get_pixel(GB_gameboy_t *gb, uint8_t x, uint8_t y)
         return gb->sprite_palletes_rgb[sprite_palette * 4 + sprite_pixel];
     }
 
-    if (!bg_enabled) {
+    if (bg_enabled) {
-        return gb->background_palletes_rgb[0];
-    }
-
         if (gb->io_registers[GB_IO_LCDC] & 0x10) {
             tile_address = tile * 0x10;
         }
@@ -168,6 +165,7 @@ static uint32_t get_pixel(GB_gameboy_t *gb, uint8_t x, uint8_t y)
 
         background_pixel = (((gb->vram[tile_address + (y & 7) * 2    ] >> ((~x)&7)) & 1 ) |
                             ((gb->vram[tile_address + (y & 7) * 2 + 1] >> ((~x)&7)) & 1) << 1 );
+    }
 
     if (priority && sprite_pixel && !background_pixel) {
         if (!gb->cgb_mode) {

Core/gb.h

@@ -226,6 +226,7 @@ typedef struct GB_gameboy_s {
         bool stopped;
         bool boot_rom_finished;
         bool ime_toggle; /* ei (and di in CGB) have delayed effects.*/
+        bool halt_bug;
 
         /* Misc state*/
         /* IR */

Core/joypad.c

@@ -22,6 +22,13 @@ void GB_update_joyp(GB_gameboy_t *gb)
             for (uint8_t i = 0; i < 4; i++) {
                 gb->io_registers[GB_IO_JOYP] |= (!gb->keys[i]) << i;
             }
+            /* Forbid pressing two opposing keys, this breaks a lot of games; even if it's somewhat possible. */
+            if (!(gb->io_registers[GB_IO_JOYP] & 1)) {
+                gb->io_registers[GB_IO_JOYP] |= 2;
+            }
+            if (!(gb->io_registers[GB_IO_JOYP] & 4)) {
+                gb->io_registers[GB_IO_JOYP] |= 8;
+            }
             break;
 
         case 1:

Core/memory.c

@@ -74,7 +74,7 @@ static uint8_t read_vram(GB_gameboy_t *gb, uint16_t addr)
 
 static uint8_t read_mbc_ram(GB_gameboy_t *gb, uint16_t addr)
 {
-    if (!gb->mbc_ram_enable) return 0xFF;
+    if (!gb->mbc_ram_enable || !gb->mbc_ram_size) return 0xFF;
     
     if (gb->cartridge_type->has_rtc && gb->mbc_ram_bank >= 8 && gb->mbc_ram_bank <= 0xC) {
         /* RTC read */
@@ -319,7 +319,7 @@ static void write_vram(GB_gameboy_t *gb, uint16_t addr, uint8_t value)
 
 static void write_mbc_ram(GB_gameboy_t *gb, uint16_t addr, uint8_t value)
 {
-    if (!gb->mbc_ram_enable) return;
+    if (!gb->mbc_ram_enable || !gb->mbc_ram_size) return;
 
     if (gb->cartridge_type->has_rtc && gb->mbc_ram_bank >= 8 && gb->mbc_ram_bank <= 0xC) {
         /* RTC read */

Core/z80_cpu.c

@@ -684,6 +684,11 @@ static void halt(GB_gameboy_t *gb, uint8_t opcode)
 {
     GB_advance_cycles(gb, 4);
     gb->halted = true;
+    /* Despite what some online documentations say, the HALT bug also happens on a CGB, in both CGB and DMG modes. */
+    if (!gb->ime && (gb->interrupt_enable & gb->io_registers[GB_IO_IF] & 0x1F) != 0) {
+        gb->halted = false;
+        gb->halt_bug = true;
+    }
 }
 
 static void ret_cc(GB_gameboy_t *gb, uint8_t opcode)
@@ -1332,12 +1337,9 @@ static GB_opcode_t *opcodes[256] = {
 void GB_cpu_run(GB_gameboy_t *gb)
 {
     gb->vblank_just_occured = false;
-    bool interrupt = gb->interrupt_enable & gb->io_registers[GB_IO_IF];
+    bool interrupt = gb->interrupt_enable & gb->io_registers[GB_IO_IF] & 0x1F;
-    bool halt_bug = false;
 
     if (interrupt) {
-        /* Despite what some online documentations say, the HALT bug also happens on a CGB, in both CGB and DMG modes. */
-        halt_bug = gb->halted;
         gb->halted = false;
     }
 
@@ -1354,7 +1356,7 @@ void GB_cpu_run(GB_gameboy_t *gb)
 
     if (effecitve_ime && interrupt) {
         uint8_t interrupt_bit = 0;
-        uint8_t interrupt_queue = gb->interrupt_enable & gb->io_registers[GB_IO_IF];
+        uint8_t interrupt_queue = gb->interrupt_enable & gb->io_registers[GB_IO_IF] & 0x1F;
         while (!(interrupt_queue & 1)) {
             interrupt_queue >>= 1;
             interrupt_bit++;
@@ -1367,8 +1369,9 @@ void GB_cpu_run(GB_gameboy_t *gb)
     }
     else if(!gb->halted && !gb->stopped) {
         uint8_t opcode = GB_read_memory(gb, gb->pc++);
-        if (halt_bug) {
+        if (gb->halt_bug) {
             gb->pc--;
+            gb->halt_bug = false;
         }
         opcodes[opcode](gb, opcode);
     }