@@ -9,6 +9,8 @@ #include "gba/io.h"
 #include "gba/serialize.h"
 #include "util/hash.h"
 
+const int GBA_LUX_LEVELS[10] = { 5, 11, 18, 27, 42, 62, 84, 109, 139, 183 };
+
 static void _readPins(struct GBACartridgeHardware* hw);
 static void _outputPins(struct GBACartridgeHardware* hw, unsigned pins);
 

@@ -79,6 +79,8 @@
 	int32_t (*readGyroZ)(struct GBARotationSource*);
 };
 
+extern const int GBA_LUX_LEVELS[10];
+
 struct GBALuminanceSource {
 	void (*sample)(struct GBALuminanceSource*);
 

@@ -8,6 +8,7 @@
 #include "util/common.h"
 
 #include "gba/gba.h"
+#include "gba/interface.h"
 #include "gba/renderers/video-software.h"
 #include "gba/serialize.h"
 #include "gba/supervisor/overrides.h"
@@ -17,6 +18,8 @@ #include "util/vfs.h"
 
 #define SAMPLES 1024
 #define RUMBLE_PWM 35
+
+#define SOLAR_SENSOR_LEVEL "mgba_solar_sensor_level"
 
 static retro_environment_t environCallback;
 static retro_video_refresh_t videoCallback;
@@ -31,6 +34,8 @@
 static void _postAudioBuffer(struct GBAAVStream*, struct GBAAudio* audio);
 static void _postVideoFrame(struct GBAAVStream*, struct GBAVideoRenderer* renderer);
 static void _setRumble(struct GBARumble* rumble, int enable);
+static uint8_t _readLux(struct GBALuminanceSource* lux);
+static void _updateLux(struct GBALuminanceSource* lux);
 
 static struct GBA gba;
 static struct ARMCore cpu;
@@ -44,6 +49,8 @@ static struct GBAAVStream stream;
 static int rumbleLevel;
 static struct CircleBuffer rumbleHistory;
 static struct GBARumble rumble;
+static struct GBALuminanceSource lux;
+static int luxLevel;
 
 unsigned retro_api_version(void) {
    return RETRO_API_VERSION;
@@ -51,6 +58,13 @@ }
 
 void retro_set_environment(retro_environment_t env) {
 	environCallback = env;
+
+	struct retro_variable vars[] = {
+		{ SOLAR_SENSOR_LEVEL, "Solar sensor level; 0|1|2|3|4|5|6|7|8|9|10" },
+		{ 0, 0 }
+	};
+
+	environCallback(RETRO_ENVIRONMENT_SET_VARIABLES, vars);
 }
 
 void retro_set_video_refresh(retro_video_refresh_t video) {
@@ -130,6 +144,11 @@ } else {
 		rumbleCallback = 0;
 	}
 
+	luxLevel = 0;
+	lux.readLuminance = _readLux;
+	lux.sample = _updateLux;
+	_updateLux(&lux);
+
 	struct retro_log_callback log;
 	if (environCallback(RETRO_ENVIRONMENT_GET_LOG_INTERFACE, &log)) {
 		logCallback = log.log;
@@ -151,6 +170,7 @@ gba.idleOptimization = IDLE_LOOP_REMOVE; // TODO: Settings
 	if (rumbleCallback) {
 		gba.rumble = &rumble;
 	}
+	gba.luminanceSource = &lux;
 	rom = 0;
 
 	const char* sysDir = 0;
@@ -401,3 +421,40 @@ }
 	CircleBufferWrite8(&rumbleHistory, enable);
 	rumbleCallback(0, RETRO_RUMBLE_STRONG, rumbleLevel * 0xFFFF / RUMBLE_PWM);
 }
+
+static void _updateLux(struct GBALuminanceSource* lux) {
+	UNUSED(lux);
+	struct retro_variable var = {
+		.key = SOLAR_SENSOR_LEVEL,
+		.value = 0
+	};
+
+	bool updated = false;
+	if (!environCallback(RETRO_ENVIRONMENT_GET_VARIABLE_UPDATE, &updated) || !updated) {
+		return;
+	}
+	if (!environCallback(RETRO_ENVIRONMENT_GET_VARIABLE, &var) || !var.value) {
+		return;
+	}
+
+	char* end;
+	int newLuxLevel = strtol(var.value, &end, 10);
+	if (!*end) {
+		if (newLuxLevel > 10) {
+			luxLevel = 10;
+		} else if (newLuxLevel < 0) {
+			luxLevel = 0;
+		} else {
+			luxLevel = newLuxLevel;
+		}
+	}
+}
+
+static uint8_t _readLux(struct GBALuminanceSource* lux) {
+	UNUSED(lux);
+	int value = 0x16;
+	if (luxLevel > 0) {
+		value += GBA_LUX_LEVELS[luxLevel - 1];
+	}
+	return 0xFF - value;
+}

@@ -29,8 +29,6 @@
 using namespace QGBA;
 using namespace std;
 
-const int GameController::LUX_LEVELS[10] = { 5, 11, 18, 27, 42, 62, 84, 109, 139, 183 };
-
 GameController::GameController(QObject* parent)
 	: QObject(parent)
 	, m_drawContext(new uint32_t[256 * 256])
@@ -794,7 +792,7 @@ m_luxValue = value;
 	value = std::max<int>(value - 0x16, 0);
 	m_luxLevel = 10;
 	for (int i = 0; i < 10; ++i) {
-		if (value < LUX_LEVELS[i]) {
+		if (value < GBA_LUX_LEVELS[i]) {
 			m_luxLevel = i;
 			break;
 		}
@@ -806,7 +804,7 @@ void GameController::setLuminanceLevel(int level) {
 	int value = 0x16;
 	level = std::max(0, std::min(10, level));
 	if (level > 0) {
-		value += LUX_LEVELS[level - 1];
+		value += GBA_LUX_LEVELS[level - 1];
 	}
 	setLuminanceValue(value);
 }

@@ -207,8 +207,6 @@ } m_lux;
 	uint8_t m_luxValue;
 	int m_luxLevel;
 
-	static const int LUX_LEVELS[10];
-
 	GBARTCGenericSource m_rtc;
 };