brightness notes.txt

AI ramblings on possible way of doing brightness control:

Android:

Declare the WRITE_SETTINGS permission in your AndroidManifest.xml file

Brightness from 0 to 255

#include <jni.h>
#include <android/log.h>
#include <android/native_window.h>
#include <android/native_window_jni.h>
#include <android/provider/Settings.h>

// Function to set brightness
void setBrightness(JNIEnv* env, jobject context, int brightness) {
    // Constrain the value of brightness
    if (brightness < 0) brightness = 0;
    else if (brightness > 255) brightness = 255;

    jclass activityClass = env->GetObjectClass(context);
    jmethodID getContentResolver = env->GetMethodID(activityClass, "getContentResolver", "()Landroid/content/ContentResolver;");
    jobject cResolver = env->CallObjectMethod(context, getContentResolver);

    jclass settingsClass = env->FindClass("android/provider/Settings$System");
    jfieldID screenBrightness = env->GetStaticFieldID(settingsClass, "SCREEN_BRIGHTNESS", "Ljava/lang/String;");
    jstring brightnessSetting = static_cast<jstring>(env->GetStaticObjectField(settingsClass, screenBrightness));

    jmethodID putInt = env->GetStaticMethodID(settingsClass, "putInt", "(Landroid/content/ContentResolver;Ljava/lang/String;I)Z");
    env->CallStaticBooleanMethod(settingsClass, putInt, cResolver, brightnessSetting, brightness);
}

// Function to get current brightness
int getCurrentBrightness(JNIEnv* env, jobject context) {
    ContentResolver cResolver = context->getContentResolver();
    return Settings.System.getInt(cResolver, Settings.System.SCREEN_BRIGHTNESS, 0);
}


Windows:
Get:
#include <highlevelmonitorconfigurationapi.h>

// Get the monitor handle (e.g., using GetPhysicalMonitorsFromHMONITOR)
HANDLE hMonitor = ...;

DWORD minBrightness, currentBrightness, maxBrightness;
GetMonitorBrightness(hMonitor, &minBrightness, &currentBrightness, &maxBrightness);


Set:
#include <windows.h>

typedef struct _DISPLAY_BRIGHTNESS {
    UCHAR ucDisplayPolicy;
    UCHAR ucACBrightness;
    UCHAR ucDCBrightness;
} DISPLAY_BRIGHTNESS;

DISPLAY_BRIGHTNESS brightness;
brightness.ucDisplayPolicy = 0;
brightness.ucACBrightness = 0; // For testing purposes
brightness.ucDCBrightness = 0;

HANDLE h = CreateFile(L"\\\\.\\LCD", GENERIC_READ | GENERIC_WRITE, 0, NULL, OPEN_EXISTING, 0, NULL);
if (h != INVALID_HANDLE_VALUE) {
    DWORD ret;
    if (DeviceIoControl(h, IOCTL_VIDEO_SET_DISPLAY_BRIGHTNESS, &brightness, sizeof(brightness), NULL, 0, &ret, NULL)) {
        // Successfully set brightness
    }
    CloseHandle(h);
}