I have succefully hooked a game and I need to do read and write with GetPixel and SetPixel to the game window.

To do a test I have created this code:

Here my hooked function:

My_hooked_function(int a3)

    HWND hWnd = GetForegroundWindow();

    if (hWnd == NULL)
         hWnd = GetDesktopWindow();

    if (a3==49)

        string buf;
        LF::Log_Update("Button Pressed");
        SetWindowLongA(hWnd, GWL_WNDPROC, (LONG_PTR)&WndProc);
        // SetWindowSubclass(hWnd, &WndProc, 1, 0);
        // DrawPixels(hWnd);

here my test function to draw something in the game (that is a old 32 bit that required directx 11):

void DrawPixels(HWND hwnd) {

    RECT r;

    LF::Log_Update("DrawPixels Entrato");

    GetClientRect(hwnd, &r);

    if (r.bottom == 0) {


    HDC hdc = BeginPaint(hwnd, &ps);

    for (int i = 0; i < 1000; i++) {

        int x = rand() % r.right;
        int y = rand() % r.bottom;
        SetPixel(hdc, x, y, RGB(0, 0, 0));

        for (int i = 1; i <= 4; i++)
            SetPixel(hdc, x - i, y, RGB(0, 0, 0));
            SetPixel(hdc, x + -i, y, RGB(0, 0, 0));

            SetPixel(hdc, x, y + i, RGB(0, 0, 0));
            SetPixel(hdc, x, y - i, RGB(0, 0, 0));


    EndPaint(hwnd, &ps);


and here the window procedure callback:

    WPARAM wParam, LPARAM lParam) {

    LF::Log_Update("Enter here");


    switch (msg) {

    case WM_PAINT:

        LF::Log_Update("For some reason not enter here");



    case WM_DESTROY:

        return 0;

return DefWindowProcW(hwnd, msg, wParam, lParam);


In my code I have 2 problems:

  1. I need to attach and not replace the window procedure (SetWindowLongA is not right in this case) because the game must continue to work. I need only to paint some line to the game existing window.
  2. I have tested the function "DrawPixels" to an empty c++ windows project and If I put it in the "WM_PAINT" message of the WndProc work perfectly but not in the game.

I searching for a way to draw some pixel on a external DirectX 11 game.

Can you help me please ?

Thanks !


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