Win32 Window flickering when drawing with GDI (PE) - c++

Question

I'm trying to create a win32 semi / transparent window, on which I could draw with another program on it with GDI+ api
When i'm drawing on the main window the line is staying few second on the screen
Even if the double buffering is enabled with WS_EX_COMPOSITED in SetWindowLong
How can i disable this flickering ? I'm pretty sure the problem is from my window because i don't have this problem on other window
My WinMain
int WINAPI WinMain(
_In_ HINSTANCE hInstance,
_In_opt_ HINSTANCE hPrevInstance,
_In_ LPSTR lpCmdLine,
_In_ int nCmdShow
)
{
WNDCLASSEX wcex;
wcex.cbSize = sizeof(WNDCLASSEX);
wcex.style = 0;
wcex.lpfnWndProc = WndProc;
wcex.cbClsExtra = 0;
wcex.cbWndExtra = 0;
wcex.hInstance = hInstance;
wcex.hIcon = LoadIcon(wcex.hInstance, IDI_APPLICATION);
wcex.hCursor = LoadCursor(NULL, IDC_ARROW);
wcex.hbrBackground = (HBRUSH)(COLOR_WINDOW+1);
wcex.lpszMenuName = NULL;
wcex.lpszClassName = szWindowClass;
wcex.hIconSm = LoadIcon(wcex.hInstance, IDI_APPLICATION);
if (!RegisterClassEx(&wcex))
{
MessageBox(NULL,
_T("Call to RegisterClassEx failed!"),
_T("Windows Desktop Guided Tour"),
0);
return 1;
}
hInst = hInstance;
HWND hWnd = CreateWindowEx(
0,
szWindowClass,
szTitle,
WS_POPUP,
CW_USEDEFAULT, CW_USEDEFAULT,
1280, 720,
NULL,
NULL,
hInstance,
NULL
);
if (!hWnd)
{
MessageBox(NULL,
_T("Call to CreateWindow failed!"),
_T("Windows Desktop Guided Tour"),
0);
return 1;
}
MSG msg;
SetWindowLong(hWnd, GWL_EXSTYLE, WS_EX_LAYERED | WS_EX_TRANSPARENT | WS_EX_COMPOSITED);
SetLayeredWindowAttributes(hWnd, RGB(0, 0, 0), (255 * 50) / 100, LWA_ALPHA); //50%
ShowWindow(hWnd, SW_SHOW);
UpdateWindow(hWnd);
while(GetMessage(&msg,NULL,0,0)){
TranslateMessage(&msg);
DispatchMessage(&msg);
}return(int)msg.wParam;
}
and my WndProc
LRESULT CALLBACK WndProc(HWND hWnd, UINT message, WPARAM wParam, LPARAM lParam)
{
switch (message)
{
case WM_DESTROY:
PostQuitMessage(0);
break;
default:
return DefWindowProc(hWnd, message, wParam, lParam);
break;
}
return 0;
}
Here my code for drawing on the main window
while(1){
DrawLine(ScreenX, ScreenY/2,ScreenX/2 , id, targethdc);
Sleep(1);
id++;
if(id >= ScreenY){
id=0;
}
}
void DrawLine(float StartX, float StartY, float EndX, float EndY, HDC hdc)
{
int a, b = 0;
HPEN hOPen;
HPEN hNPen = CreatePen(PS_SOLID, 2, RGB(255,0,0));// penstyle, width, color
hOPen = (HPEN)SelectObject(hdc, hNPen);
MoveToEx(hdc, StartX, StartY, NULL); //start
a = LineTo(hdc, EndX, EndY); //end
DeleteObject(SelectObject(hdc, hOPen));
}
Thx