1x1 black pixel overlay to workaround my issue of HDR video briefly flickering when cursor auto-hides/reappears or leaves/enters main screen

hdrfix.c

#include <windows.h>

#define IDM_EXIT 1001
#define WM_TRAYICON (WM_USER + 1)

static NOTIFYICONDATA nid;
static HMENU tray_menu;

LRESULT CALLBACK WndProc(HWND hwnd, UINT msg, WPARAM wp, LPARAM lp) {
    switch (msg) {
        case WM_PAINT: {
            PAINTSTRUCT ps;
            HDC hdc = BeginPaint(hwnd, &ps);
            FillRect(hdc, &ps.rcPaint, (HBRUSH)GetStockObject(BLACK_BRUSH));
            EndPaint(hwnd, &ps);
            return 0;
        }
        case WM_TRAYICON:
            if (lp == WM_RBUTTONUP) {
                POINT pt;
                GetCursorPos(&pt);
                SetForegroundWindow(hwnd);
                TrackPopupMenu(tray_menu, TPM_RIGHTBUTTON, pt.x, pt.y, 0, hwnd, NULL);
            }
            return 0;
        case WM_COMMAND:
            if (LOWORD(wp) == IDM_EXIT) {
                Shell_NotifyIcon(NIM_DELETE, &nid);
                PostQuitMessage(0);
            }
            return 0;
        case WM_DESTROY:
            Shell_NotifyIcon(NIM_DELETE, &nid);
            PostQuitMessage(0);
            return 0;
    }
    return DefWindowProc(hwnd, msg, wp, lp);
}

int WINAPI WinMain(HINSTANCE hInst, HINSTANCE hPrev, LPSTR lpCmd, int nShow) {
    WNDCLASS wc = {0};
    wc.lpfnWndProc   = WndProc;
    wc.hInstance     = hInst;
    wc.lpszClassName = "HDRFix";
    wc.hbrBackground = (HBRUSH)GetStockObject(BLACK_BRUSH);
    RegisterClass(&wc);

    HWND hwnd = CreateWindowEx(
        WS_EX_TOPMOST | WS_EX_TOOLWINDOW | WS_EX_NOACTIVATE,
        "HDRFix", NULL, WS_POPUP,
        0, 0, 1, 1,
        NULL, NULL, hInst, NULL
    );

    ShowWindow(hwnd, SW_SHOWNOACTIVATE);
    UpdateWindow(hwnd);

    /* Tray icon */
    tray_menu = CreatePopupMenu();
    AppendMenu(tray_menu, MF_STRING, IDM_EXIT, "Exit HDRFix");

    nid.cbSize           = sizeof(nid);
    nid.hWnd             = hwnd;
    nid.uID              = 1;
    nid.uFlags           = NIF_ICON | NIF_TIP | NIF_MESSAGE;
    nid.uCallbackMessage = WM_TRAYICON;
    nid.hIcon            = LoadIcon(NULL, IDI_APPLICATION);
    lstrcpy(nid.szTip, "HDRFix - right-click to exit");
    Shell_NotifyIcon(NIM_ADD, &nid);

    MSG msg;
    while (GetMessage(&msg, NULL, 0, 0)) {
        TranslateMessage(&msg);
        DispatchMessage(&msg);
    }
    return 0;
}

compiled with
cl hdrfix.c /O2 /Fe:HDRFix.exe /link user32.lib gdi32.lib shell32.lib or
x86_64-w64-mingw32-gcc -O2 -mwindows -o HDRFix.exe hdrfix.c -lshell32