如何在C/C++应用中读写Windows显示器变暗相关电源设置？

要在C/C++应用里搞定Windows的“Dim the display after”和“Display dimming brightness”这两个高级电源设置，咱们得用到Windows提供的电源计划API（主要是PowrProf.h里的函数）。下面一步步给你拆解查询和设置的实现方式：

首先，你需要获取当前活动电源计划的句柄，然后分别针对AC（插电）和DC（电池）场景读取对应的值。这里要用到几个预定义的GUID，它们对应电源计划里的显示子组和具体设置项：

• 显示设置子组：GUID_DISPLAY_SUBGROUP
• 变暗超时（AC/DC通用）：GUID_VIDEO_DIM_TIMEOUT
• 变暗亮度（AC/DC通用）：GUID_VIDEO_DIM_BRIGHTNESS

以下是完整的查询示例代码：

#include <Windows.h>
#include <PowrProf.h>
#include <iostream>

// 链接PowrProf库，编译时需要
#pragma comment(lib, "PowrProf.lib")

int main() {
    // 获取当前活动电源计划的句柄
    GUID* pActiveScheme = nullptr;
    if (PowerGetActiveScheme(nullptr, &pActiveScheme) != ERROR_SUCCESS) {
        std::cerr << "Failed to get active power scheme. Error code: " << GetLastError() << std::endl;
        return 1;
    }

    DWORD dataSize = sizeof(DWORD);
    DWORD value = 0;

    // 读取AC状态下的变暗超时（单位：秒，0表示从不变暗）
    if (PowerReadACValueIndex(nullptr, pActiveScheme, &GUID_DISPLAY_SUBGROUP, &GUID_VIDEO_DIM_TIMEOUT, &value, &dataSize) == ERROR_SUCCESS) {
        std::cout << "AC - Dim display after: " << value << " seconds" << std::endl;
    } else {
        std::cerr << "Failed to read AC dim timeout. Error code: " << GetLastError() << std::endl;
    }

    // 读取DC状态下的变暗超时
    dataSize = sizeof(DWORD);
    if (PowerReadDCValueIndex(nullptr, pActiveScheme, &GUID_DISPLAY_SUBGROUP, &GUID_VIDEO_DIM_TIMEOUT, &value, &dataSize) == ERROR_SUCCESS) {
        std::cout << "DC - Dim display after: " << value << " seconds" << std::endl;
    } else {
        std::cerr << "Failed to read DC dim timeout. Error code: " << GetLastError() << std::endl;
    }

    // 读取AC状态下的变暗亮度（0-100，百分比）
    dataSize = sizeof(DWORD);
    if (PowerReadACValueIndex(nullptr, pActiveScheme, &GUID_DISPLAY_SUBGROUP, &GUID_VIDEO_DIM_BRIGHTNESS, &value, &dataSize) == ERROR_SUCCESS) {
        std::cout << "AC - Display dimming brightness: " << value << "%" << std::endl;
    } else {
        std::cerr << "Failed to read AC dim brightness. Error code: " << GetLastError() << std::endl;
    }

    // 读取DC状态下的变暗亮度
    dataSize = sizeof(DWORD);
    if (PowerReadDCValueIndex(nullptr, pActiveScheme, &GUID_DISPLAY_SUBGROUP, &GUID_VIDEO_DIM_BRIGHTNESS, &value, &dataSize) == ERROR_SUCCESS) {
        std::cout << "DC - Display dimming brightness: " << value << "%" << std::endl;
    } else {
        std::cerr << "Failed to read DC dim brightness. Error code: " << GetLastError() << std::endl;
    }

    // 释放资源
    CloseHandle(pActiveScheme);
    return 0;
}

设置流程和查询类似，只是把读取函数换成PowerWriteACValueIndex和PowerWriteDCValueIndex。修改完成后，需要调用PowerSetActiveScheme提交更改，确保设置生效。

以下是完整的设置示例代码：

#include <Windows.h>
#include <PowrProf.h>
#include <iostream>

#pragma comment(lib, "PowrProf.lib")

int main() {
    // 获取当前活动电源计划句柄
    GUID* pActiveScheme = nullptr;
    if (PowerGetActiveScheme(nullptr, &pActiveScheme) != ERROR_SUCCESS) {
        std::cerr << "Failed to get active power scheme. Error code: " << GetLastError() << std::endl;
        return 1;
    }

    // --------------------------
    // 设置AC状态下的参数
    // --------------------------
    // 10分钟后变暗（600秒）
    const DWORD acDimTimeout = 600;
    if (PowerWriteACValueIndex(nullptr, pActiveScheme, &GUID_DISPLAY_SUBGROUP, &GUID_VIDEO_DIM_TIMEOUT, acDimTimeout) != ERROR_SUCCESS) {
        std::cerr << "Failed to set AC dim timeout. Error code: " << GetLastError() << std::endl;
        CloseHandle(pActiveScheme);
        return 1;
    }

    // 变暗后亮度为50%
    const DWORD acDimBrightness = 50;
    if (PowerWriteACValueIndex(nullptr, pActiveScheme, &GUID_DISPLAY_SUBGROUP, &GUID_VIDEO_DIM_BRIGHTNESS, acDimBrightness) != ERROR_SUCCESS) {
        std::cerr << "Failed to set AC dim brightness. Error code: " << GetLastError() << std::endl;
        CloseHandle(pActiveScheme);
        return 1;
    }

    // --------------------------
    // 设置DC状态下的参数
    // --------------------------
    // 5分钟后变暗（300秒）
    const DWORD dcDimTimeout = 300;
    if (PowerWriteDCValueIndex(nullptr, pActiveScheme, &GUID_DISPLAY_SUBGROUP, &GUID_VIDEO_DIM_TIMEOUT, dcDimTimeout) != ERROR_SUCCESS) {
        std::cerr << "Failed to set DC dim timeout. Error code: " << GetLastError() << std::endl;
        CloseHandle(pActiveScheme);
        return 1;
    }

    // 变暗后亮度为30%
    const DWORD dcDimBrightness = 30;
    if (PowerWriteDCValueIndex(nullptr, pActiveScheme, &GUID_DISPLAY_SUBGROUP, &GUID_VIDEO_DIM_BRIGHTNESS, dcDimBrightness) != ERROR_SUCCESS) {
        std::cerr << "Failed to set DC dim brightness. Error code: " << GetLastError() << std::endl;
        CloseHandle(pActiveScheme);
        return 1;
    }

    // 提交更改，确保设置生效
    if (PowerSetActiveScheme(nullptr, pActiveScheme) != ERROR_SUCCESS) {
        std::cerr << "Failed to apply power scheme changes. Error code: " << GetLastError() << std::endl;
        CloseHandle(pActiveScheme);
        return 1;
    }

    std::cout << "Power settings updated successfully!" << std::endl;

    // 释放资源
    CloseHandle(pActiveScheme);
    return 0;
}

• 权限要求：修改电源计划设置需要管理员权限，如果你的应用没有以管理员身份运行，调用写入函数会返回ERROR_ACCESS_DENIED错误。
• 参数范围：
  • 超时值：0表示从不变暗，其他值为秒数，Windows UI通常限制在1分钟到5小时，但API支持更大的数值。
  • 亮度值：0-100的整数，代表百分比，0是最暗，100表示变暗后亮度和原始亮度一致（相当于不变暗）。
• 编译链接：必须链接PowrProf.lib库，代码里的#pragma comment(lib, "PowrProf.lib")已经自动处理了这一点，也可以在项目设置中手动添加该库。

内容的提问来源于stack exchange，提问作者Willy K.