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libretro: Fix Boktai 1 solar sensor 8-bar mapping, add External Solar Sensor device for chord-based solar input #316

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libretro: Fix Boktai 1 solar sensor 8-bar mapping, add External Solar Sensor device for chord-based solar input #316

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b0d63c0
libretro: Add chord mode solar sensor input and fix Boktai 1 8-bar ma…
TideGear Jan 24, 2026
78431e5
libretro: Harden solar input handling and fix Android ndk-build
TideGear Jan 24, 2026
04762c9
Revert "libretro: Harden solar input handling and fix Android ndk-build"
TideGear Jan 30, 2026
7b3a805
Revert "libretro: Add chord mode solar sensor input and fix Boktai 1 …
TideGear Jan 30, 2026
7441e38
libretro: Fix Boktai 1 solar sensor 8-bar mapping
TideGear Jan 30, 2026
64e1a82
libretro: Add External Solar Sensor device for chord-based solar input
TideGear Jan 31, 2026
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191 changes: 170 additions & 21 deletions src/platform/libretro/libretro.c
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Original file line number Diff line number Diff line change
Expand Up @@ -55,6 +55,7 @@ static unsigned targetSampleRate = GBA_RESAMPLED_RATE;
#define VIDEO_WIDTH_MAX 256
#define VIDEO_HEIGHT_MAX 224
#define VIDEO_BUFF_SIZE (VIDEO_WIDTH_MAX * VIDEO_HEIGHT_MAX * sizeof(mColor))
#define LIBRETRO_MAX_PORTS 8

static retro_environment_t environCallback;
static retro_video_refresh_t videoCallback;
Expand All @@ -75,6 +76,9 @@ static void _audioRateChanged(struct mAVStream*, unsigned rate);
static void _setRumble(struct mRumbleIntegrator*, float level);
static uint8_t _readLux(struct GBALuminanceSource* lux);
static void _updateLux(struct GBALuminanceSource* lux);
static int _boktai1StepToBar(int step);
static int _boktai1BarToStep(int bar);
static int _analogStickSolarLevel(unsigned port);
static void _updateCamera(const uint32_t* buffer, unsigned width, unsigned height, size_t pitch);
static void _startImage(struct mImageSource*, unsigned w, unsigned h, int colorFormats);
static void _stopImage(struct mImageSource*);
Expand Down Expand Up @@ -106,6 +110,8 @@ static int luxLevelIndex;
static uint8_t luxLevel;
static bool luxSensorEnabled;
static bool luxSensorUsed;
static bool luxAnalogMode;
static bool boktai1Game;
static struct mLogger logger;
static struct retro_camera_callback cam;
static struct mImageSource imageSource;
Expand Down Expand Up @@ -1436,6 +1442,7 @@ void retro_init(void) {
envVarsUpdated = true;
luxSensorUsed = false;
luxSensorEnabled = false;
boktai1Game = false;
luxLevelIndex = 0;
luxLevel = 0;
lux.readLuminance = _readLux;
Expand Down Expand Up @@ -1607,23 +1614,60 @@ void retro_run(void) {
core->setKeys(core, keys);

if (!luxSensorUsed) {
static bool wasAdjustingLux = false;
if (wasAdjustingLux) {
wasAdjustingLux = inputCallback(0, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_R3) ||
inputCallback(0, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_L3);
} else {
if (inputCallback(0, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_R3)) {
++luxLevelIndex;
if (luxLevelIndex > 10) {
luxLevelIndex = 10;
if (luxAnalogMode) {
int level = -1;
unsigned port;
for (port = 0; port < LIBRETRO_MAX_PORTS; ++port) {
level = _analogStickSolarLevel(port);
if (level >= 0) {
break;
}
}
if (level >= 0) {
if (boktai1Game) {
if (level > 8) {
level = 8;
}
luxLevelIndex = _boktai1BarToStep(level);
} else {
luxLevelIndex = level;
}
wasAdjustingLux = true;
} else if (inputCallback(0, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_L3)) {
--luxLevelIndex;
if (luxLevelIndex < 0) {
luxLevelIndex = 0;
}
} else {
static bool wasAdjustingLux = false;
if (wasAdjustingLux) {
wasAdjustingLux = inputCallback(0, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_R3) ||
inputCallback(0, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_L3);
} else {
if (inputCallback(0, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_R3)) {
if (boktai1Game) {
int bar = _boktai1StepToBar(luxLevelIndex);
if (bar < 8) {
++bar;
}
luxLevelIndex = _boktai1BarToStep(bar);
} else {
++luxLevelIndex;
if (luxLevelIndex > 10) {
luxLevelIndex = 10;
}
}
wasAdjustingLux = true;
} else if (inputCallback(0, RETRO_DEVICE_JOYPAD, 0, RETRO_DEVICE_ID_JOYPAD_L3)) {
if (boktai1Game) {
int bar = _boktai1StepToBar(luxLevelIndex);
if (bar > 0) {
--bar;
}
luxLevelIndex = _boktai1BarToStep(bar);
} else {
--luxLevelIndex;
if (luxLevelIndex < 0) {
luxLevelIndex = 0;
}
}
wasAdjustingLux = true;
}
wasAdjustingLux = true;
}
}
}
Expand Down Expand Up @@ -2088,6 +2132,22 @@ bool retro_load_game(const struct retro_game_info* game) {
core->loadROM(core, rom);
deferredSetup = true;

/* Boktai 1 has an 8-bar solar gauge. Detect it once per loaded game so
* manual adjustments (core option level + L3/R3) operate in 0-8 bars. */
boktai1Game = false;
#ifdef M_CORE_GBA
if (core->platform(core) == mPLATFORM_GBA) {
struct mGameInfo info;
core->getGameInfo(core, &info);
boktai1Game = strcmp(info.code, "U3IJ") == 0 ||
strcmp(info.code, "U3IE") == 0 ||
strcmp(info.code, "U3IP") == 0;
}
#endif
/* Re-apply solar settings with the correct mapping for this title. */
envVarsUpdated = true;
_updateLux(&lux);

const char* sysDir = 0;
const char* biosName = 0;
char biosPath[PATH_MAX];
Expand Down Expand Up @@ -2154,6 +2214,7 @@ void retro_unload_game(void) {
if (!core) {
return;
}
boktai1Game = false;
mCoreConfigDeinit(&core->config);
core->deinit(core);
mappedMemoryFree(data, dataSize);
Expand Down Expand Up @@ -2466,6 +2527,81 @@ static void _setRumble(struct mRumbleIntegrator* rumble, float level) {
rumbleCallback(0, RETRO_RUMBLE_WEAK, level * 0xFFFF);
}

static int _boktai1StepToBar(int step) {
static const uint8_t map[11] = { 0, 1, 2, 3, 3, 4, 5, 6, 7, 7, 8 };
if (step < 0) {
step = 0;
} else if (step > 10) {
step = 10;
}
return map[step];
}

static int _boktai1BarToStep(int bar) {
static const uint8_t map[9] = { 0, 1, 2, 3, 5, 6, 7, 8, 10 };
if (bar < 0) {
bar = 0;
} else if (bar > 8) {
bar = 8;
}
return map[bar];
}

static int _analogStickSolarLevel(unsigned port) {
const int16_t dead = 0x4000;
int16_t lx = inputCallback(port, RETRO_DEVICE_ANALOG,
RETRO_DEVICE_INDEX_ANALOG_LEFT,
RETRO_DEVICE_ID_ANALOG_X);
int16_t ly = inputCallback(port, RETRO_DEVICE_ANALOG,
RETRO_DEVICE_INDEX_ANALOG_LEFT,
RETRO_DEVICE_ID_ANALOG_Y);
int16_t rx = inputCallback(port, RETRO_DEVICE_ANALOG,
RETRO_DEVICE_INDEX_ANALOG_RIGHT,
RETRO_DEVICE_ID_ANALOG_X);
int16_t ry = inputCallback(port, RETRO_DEVICE_ANALOG,
RETRO_DEVICE_INDEX_ANALOG_RIGHT,
RETRO_DEVICE_ID_ANALOG_Y);

int group = -1;
if (ly < -dead) {
group = 0; /* 0-3 */
} else if (ly > dead) {
group = 1; /* 4-7 */
} else if (lx < -dead) {
group = 2; /* 8-10 & 0 */
}

int select = -1;
if (ry < -dead) {
select = 0; /* 0/4/8 */
} else if (ry > dead) {
select = 1; /* 1/5/9 */
} else if (rx < -dead) {
select = 2; /* 2/6/10 */
} else if (rx > dead) {
select = 3; /* 3/7/0 */
}

if (group < 0 || select < 0) {
return -1;
}

if (group == 0) {
return select;
} else if (group == 1) {
return 4 + select;
}

if (select == 0) {
return 8;
} else if (select == 1) {
return 9;
} else if (select == 2) {
return 10;
}
return 0;
}

static void _updateLux(struct GBALuminanceSource* lux) {
UNUSED(lux);
struct retro_variable var = {
Expand All @@ -2480,24 +2616,37 @@ static void _updateLux(struct GBALuminanceSource* lux) {

if (luxVarUpdated) {
luxSensorUsed = strcmp(var.value, "sensor") == 0;
luxAnalogMode = strcmp(var.value, "analog") == 0;
}

if (luxSensorUsed) {
_initSensors();
float fLux = luxSensorEnabled ? sensorGetCallback(0, RETRO_SENSOR_ILLUMINANCE) : 0.0f;
luxLevel = cbrtf(fLux) * 8;
} else {
if (luxVarUpdated) {
if (luxVarUpdated && !luxAnalogMode) {
char* end;
int newLuxLevelIndex = strtol(var.value, &end, 10);

if (!*end) {
if (newLuxLevelIndex > 10) {
luxLevelIndex = 10;
} else if (newLuxLevelIndex < 0) {
luxLevelIndex = 0;
if (boktai1Game) {
/* Boktai 1 shows an 8-bar gauge (0-8). Clamp any user-provided
* values outside that range, then map into the internal 10-step
* lux level indices. */
if (newLuxLevelIndex > 8) {
newLuxLevelIndex = 8;
} else if (newLuxLevelIndex < 0) {
newLuxLevelIndex = 0;
}
luxLevelIndex = _boktai1BarToStep(newLuxLevelIndex);
} else {
luxLevelIndex = newLuxLevelIndex;
if (newLuxLevelIndex > 10) {
luxLevelIndex = 10;
} else if (newLuxLevelIndex < 0) {
luxLevelIndex = 0;
} else {
luxLevelIndex = newLuxLevelIndex;
}
}
}
}
Expand Down
5 changes: 3 additions & 2 deletions src/platform/libretro/libretro_core_options.h
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Original file line number Diff line number Diff line change
Expand Up @@ -271,11 +271,12 @@ struct retro_core_option_v2_definition option_defs_us[] = {
"mgba_solar_sensor_level",
"Solar Sensor Level",
NULL,
"Sets ambient sunlight intensity. Can be used by games that included a solar sensor in their cartridges, e.g: the Boktai series.",
"Sets sunlight intensity for games that include a solar sensor in their cartridge (e.g. Boktai). 'Analog Stick Control': left stick selects group (Up=0-3, Down=4-7, Left=8-10/0); right stick selects value (Up=0/4/8, Down=1/5/9, Left=2/6/10, Right=3/7/0). ASC disables Analog to Digital until restart.",
NULL,
"input",
{
{ "sensor", "Use device sensor if available" },
{ "sensor", "Use Device Sensor If Available" },
{ "analog", "Analog Stick Control" },
{ "0", NULL },
{ "1", NULL },
{ "2", NULL },
Expand Down