DirectX9 Windows-Desktop-App transparency problems - c++

Question

I wrote a simple directX9 app (code below) which is working fine for at least 25 Windows 10 setups but on one the background of the window is just black instead of transparent (with the test draw on it).
All the systems are running dedicated NVIDIA GPUs (10 series) so this should not be the problem and they use the latest Windows 10 version with the latest Nvidia drivers.
A workaround is to add LWA_COLORKEY to SetLayeredWindowAttributes but I would like to know how I can fix the system instead of using LWA_COLORKEY. (Because adding LWA_COLORKEY costs a lot of performance).
SetLayeredWindowAttributes(hWnd, 0, 255, LWA_ALPHA | LWA_COLORKEY);
This is a sample that can replicate the problem:
#pragma once
#include <Windows.h>
#include <string>
#include <iostream>
// DirectX9
#pragma warning( push )
#pragma warning( disable : 4005)
#include <d3d9.h>
#include <d3dx9.h>
#include <Dwmapi.h>
#include <TlHelp32.h>
#include <Directxmath.h>
#pragma comment(lib, "d3dx9.lib")
#pragma comment(lib, "d3d9.lib")
#pragma comment(lib, "Dwmapi.lib")
#pragma warning( pop )
using namespace std;
using namespace DirectX;
int s_width = 800;
int s_height = 600;
#define CENTERX (GetSystemMetrics(SM_CXSCREEN)/2)-(s_width/2)
#define CENTERY (GetSystemMetrics(SM_CYSCREEN)/2)-(s_height/2)
LPDIRECT3D9 d3d;
LPDIRECT3DDEVICE9 d3ddev;
HWND hWnd;
LPD3DXFONT pFont;
LRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam);
void initD3D(HWND hWnd)
{
d3d = Direct3DCreate9(D3D_SDK_VERSION);
D3DPRESENT_PARAMETERS d3dpp;
ZeroMemory(&d3dpp, sizeof(d3dpp));
d3dpp.Windowed = TRUE;
d3dpp.SwapEffect = D3DSWAPEFFECT_DISCARD;
d3dpp.hDeviceWindow = hWnd;
d3dpp.BackBufferFormat = D3DFMT_A8R8G8B8;
d3dpp.BackBufferWidth = s_width;
d3dpp.BackBufferHeight = s_height;
d3dpp.PresentationInterval = D3DPRESENT_INTERVAL_IMMEDIATE;
d3dpp.FullScreen_RefreshRateInHz = 0;
d3dpp.EnableAutoDepthStencil = TRUE;
d3dpp.AutoDepthStencilFormat = D3DFMT_D16;
d3dpp.MultiSampleQuality = DEFAULT_QUALITY;
d3d->CreateDevice(D3DADAPTER_DEFAULT, D3DDEVTYPE_HAL, hWnd, D3DCREATE_HARDWARE_VERTEXPROCESSING, &d3dpp, &d3ddev);
D3DXCreateFont(d3ddev, 50, 0, FW_BOLD, 1, 0, DEFAULT_CHARSET, OUT_DEFAULT_PRECIS, DEFAULT_QUALITY, DEFAULT_PITCH | FF_DONTCARE, "Arial", &pFont);
}
void DrawString(int x, int y, DWORD color, LPD3DXFONT g_pFont, const char *fmt, ...)
{
RECT FontPos = { x, y, x + 120, y + 16 };
char buf[1024] = { '\0' };
va_list va_alist;
va_start(va_alist, fmt);
vsprintf_s(buf, fmt, va_alist);
va_end(va_alist);
g_pFont->DrawText(NULL, buf, -1, &FontPos, DT_NOCLIP, color);
}
void render()
{
d3ddev->Clear(0, NULL, D3DCLEAR_TARGET, D3DCOLOR_ARGB(0, 0, 0, 0), 1.0f, 0);
d3ddev->BeginScene();
DrawString(10, 50, D3DCOLOR_ARGB(100, 255, 0, 0), pFont, "Test rendering");
d3ddev->EndScene();
d3ddev->Present(NULL, NULL, NULL, NULL);
}
int main()
{
RECT rc = { 0 };
HINSTANCE hInstance = GetModuleHandle(NULL);
WNDCLASSEX wc;
ZeroMemory(&wc, sizeof(WNDCLASSEX));
wc.cbClsExtra = NULL;
wc.cbWndExtra = NULL;
wc.cbSize = sizeof(WNDCLASSEX);
wc.style = CS_HREDRAW | CS_VREDRAW;
wc.hInstance = NULL;
wc.lpfnWndProc = WindowProc;
wc.hCursor = LoadCursor(NULL, IDC_ARROW);
wc.hbrBackground = (HBRUSH)CreateSolidBrush(RGB(0, 0, 0));
wc.lpszClassName = "WindowClass";
RegisterClassEx(&wc);
hWnd = CreateWindowExA(WS_EX_LAYERED | WS_EX_TRANSPARENT, "WindowClass", "Title", WS_POPUP | WS_VISIBLE, rc.left, rc.top, s_width, s_height, NULL, NULL, hInstance, NULL);
SetLayeredWindowAttributes(hWnd, 0, 255, LWA_ALPHA);
//DWM_BLURBEHIND bb = { DWM_BB_ENABLE | DWM_BB_BLURREGION, true, CreateRectRgn(0, 0, -1, -1), true };
//if (DwmEnableBlurBehindWindow(hWnd, &bb) != S_OK)
MARGINS margin = { -1 };
DwmExtendFrameIntoClientArea(hWnd, &margin);
initD3D(hWnd);
MSG msg;
while (TRUE)
{
render();
while (PeekMessage(&msg, NULL, 0, 0, PM_REMOVE))
{
TranslateMessage(&msg);
DispatchMessage(&msg);
}
if (msg.message == WM_QUIT)
exit(0);
}
return msg.wParam;
}
LRESULT CALLBACK WindowProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message)
{
case WM_PAINT:
{
}break;
case WM_DESTROY:
{
PostQuitMessage(0);
return 0;
} break;
}
return DefWindowProc(hWnd, message, wParam, lParam);
}