SameBoy/Core/joypad.c

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#include "gb.h"
#include <assert.h>
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void GB_update_joyp(GB_gameboy_t *gb)
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{
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if (gb->model & GB_MODEL_NO_SFC_BIT) return;
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uint8_t key_selection = 0;
uint8_t previous_state = 0;
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/* Todo: add delay to key selection */
previous_state = gb->io_registers[GB_IO_JOYP] & 0xF;
key_selection = (gb->io_registers[GB_IO_JOYP] >> 4) & 3;
gb->io_registers[GB_IO_JOYP] &= 0xF0;
uint8_t current_player = gb->sgb? gb->sgb->current_player : 0;
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switch (key_selection) {
case 3:
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if (gb->sgb && gb->sgb->player_count > 1) {
gb->io_registers[GB_IO_JOYP] |= 0xF - current_player;
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}
else {
/* Nothing is wired, all up */
gb->io_registers[GB_IO_JOYP] |= 0x0F;
}
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break;
case 2:
/* Direction keys */
for (uint8_t i = 0; i < 4; i++) {
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gb->io_registers[GB_IO_JOYP] |= (!gb->keys[current_player][i]) << i;
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}
/* 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;
}
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break;
case 1:
/* Other keys */
for (uint8_t i = 0; i < 4; i++) {
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gb->io_registers[GB_IO_JOYP] |= (!gb->keys[current_player][i + 4]) << i;
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}
break;
case 0:
for (uint8_t i = 0; i < 4; i++) {
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gb->io_registers[GB_IO_JOYP] |= (!(gb->keys[current_player][i] || gb->keys[current_player][i + 4])) << i;
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}
break;
default:
__builtin_unreachable();
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break;
}
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/* Todo: This assumes the keys *always* bounce, which is incorrect when emulating an SGB */
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if (previous_state != (gb->io_registers[GB_IO_JOYP] & 0xF)) {
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/* The joypad interrupt DOES occur on CGB (Tested on CGB-E), unlike what some documents say. */
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gb->io_registers[GB_IO_IF] |= 0x10;
}
gb->io_registers[GB_IO_JOYP] |= 0xC0;
}
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void GB_icd_set_joyp(GB_gameboy_t *gb, uint8_t value)
{
uint8_t previous_state = gb->io_registers[GB_IO_JOYP] & 0xF;
gb->io_registers[GB_IO_JOYP] &= 0xF0;
gb->io_registers[GB_IO_JOYP] |= value & 0xF;
if (previous_state & ~(gb->io_registers[GB_IO_JOYP] & 0xF)) {
gb->io_registers[GB_IO_IF] |= 0x10;
}
gb->io_registers[GB_IO_JOYP] |= 0xC0;
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}
void GB_set_key_state(GB_gameboy_t *gb, GB_key_t index, bool pressed)
{
assert(index >= 0 && index < GB_KEY_MAX);
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gb->keys[0][index] = pressed;
GB_update_joyp(gb);
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}
void GB_set_key_state_for_player(GB_gameboy_t *gb, GB_key_t index, unsigned player, bool pressed)
{
assert(index >= 0 && index < GB_KEY_MAX);
assert(player < 4);
gb->keys[player][index] = pressed;
GB_update_joyp(gb);
}