GDI Double Buffer Black Flicker - c++

Question

I am using this BitBlt wrapper:
http://www.codeproject.com/Articles/21426/Double-Buffering-in-a-Win-API-Program
I initialize it in main():
biop = new Bitmap_Operations();
biop->Initialize_Buffers(m_hDC, m_hWND, 1);
biop->Create_Buffer(0);
Helper Functions:
void CreateBuffer()
{
biop->Create_Buffer(0);
}
void Render()
{
biop->Copy_to_Screen(0);
}
void ClearBuffer()
{
biop->Free_Buffer(0);
}
void DrawBox(int x, int y, int r, int g, int b, int size, int thickness)
{
// Brush style to hollow
m_LogBrush.lbStyle = BS_NULL;
// Create a logical brush and select into the context
m_hBrush = CreateBrushIndirect(&m_LogBrush);
HBRUSH hbrOldBrush = (HBRUSH)SelectObject(biop->Get_DC_Buffer(0), m_hBrush);
// Create a logical pen and select into the context
m_hPen = CreatePen(PS_SOLID, thickness, RGB(r, g, b));
HPEN hpOldPen = (HPEN)SelectObject(biop->Get_DC_Buffer(0), m_hPen);
// Draw the rectangle
Rectangle(biop->Get_DC_Buffer(0), (x - size / 2), (y - size / 2), (x + size / 2), (y + size / 2));
// Remove the object
SelectObject(biop->Get_DC_Buffer(0), hbrOldBrush); // first you must restore DC to original state
SelectObject(biop->Get_DC_Buffer(0), hpOldPen); // same here
DeleteObject(m_hBrush);
DeleteObject(m_hPen);
}
I spawn a thread to render data:
// Inside a thread
while (1)
{
CreateBuffer();
for (int i = 0; i < 1028; i++)
{
//
DrawBox()
//
}
Render();
ClearBuffer();
}
I am using FindWindow() to render on top of another application. Everything works fine, the boxes get rendered, ect, but there is a crazy full-screen flicker that seems to have a black background. My guess its when I draw from memory to the application?
I am using double buffering to avoid a flicker, but it seems like it made it worse. Any ideas?
Thanks.

Answer 1

I would use UpdateLayeredWindow APIs instead, if you need to draw transparent things on top of existing windows.