Desktop Window Manager Idle Tool

README.md

I wanted to see if there was any benefit of making Desktop Window Manager entirely idle when its running. Which includes settings its thread priorities and process priority to idle.
So feel free to test this.

You can build this project using GCC:

gcc -mwindows -s dwmidle.c -lWtsapi32 -o "DWMIdle.exe"

dwmidle.c

#include <Windows.h>
#include <stdio.h>
#include <wtsapi32.h>
#include <tlhelp32.h>

// Reference: https://learn.microsoft.com/en-us/windows/win32/api/securitybaseapi/nf-securitybaseapi-checktokenmembership#examples
BOOL IsUserAdmin()
{
    BOOL b;
    SID_IDENTIFIER_AUTHORITY NtAuthority = SECURITY_NT_AUTHORITY;
    PSID AdministratorsGroup;
    b = AllocateAndInitializeSid(
        &NtAuthority,
        2,
        SECURITY_BUILTIN_DOMAIN_RID,
        DOMAIN_ALIAS_RID_ADMINS,
        0, 0, 0, 0, 0, 0,
        &AdministratorsGroup);
    if (b)
    {
        if (!CheckTokenMembership(NULL, AdministratorsGroup, &b))
        {
            b = FALSE;
        }
        FreeSid(AdministratorsGroup);
    }

    return (b);
}

int main(int argc, char *argv[])
{

    if (!IsUserAdmin())
    {
        ShellExecute(0, "runas", argv[0], 0, 0, SW_SHOW);
        return 1;
    };
    WTS_PROCESS_INFO *pWPI;
    DWORD dwProcessCount;
    DWORD pid;
    HANDLE hThread, hProcess, hThreadSnapshot = CreateToolhelp32Snapshot(TH32CS_SNAPTHREAD, 0);
    THREADENTRY32 te;
    te.dwSize = sizeof(THREADENTRY32);

    // Reference: https://stackoverflow.com/a/42126277/16335365
    if (WTSEnumerateProcesses(WTS_CURRENT_SERVER_HANDLE, 0, 1, &pWPI, &dwProcessCount))
        for (DWORD i = 0; i < dwProcessCount; i++)
            if (!strcmp(strlwr(pWPI[i].pProcessName), "dwm.exe"))
            {
                pid = pWPI[i].ProcessId;
                break;
            };
    if (pWPI)
        WTSFreeMemory(pWPI);

    hProcess = OpenProcess(PROCESS_ALL_ACCESS, FALSE, pid);
    if (!hProcess)
        return 1;
    SetPriorityClass(hProcess, IDLE_PRIORITY_CLASS);

    if (hThreadSnapshot != INVALID_HANDLE_VALUE)
    {
        if (Thread32First(hThreadSnapshot, &te))
        {
            {
                do
                {
                    if (te.th32OwnerProcessID == pid)
                    {
                        hThread = OpenThread(THREAD_ALL_ACCESS, FALSE, te.th32ThreadID);
                        if (!SetThreadPriority(hThread, THREAD_MODE_BACKGROUND_BEGIN))
                            SetThreadPriority(hThread, THREAD_PRIORITY_IDLE);
                        SetThreadPriorityBoost(hThread, TRUE);
                        CloseHandle(hThread);
                    };
                } while (Thread32Next(hThreadSnapshot, &te));
            };
        };