How to draw lines in WM_PAINT message handler more faster?

[EDN Admin]

I want to draw a lot of lines in the WM_PAINT message handler with the following code.<br/>
<br/>
<pre class="prettyprint //DrawLine with double buffering
LRESULT CALLBACK CMyDoc::OnPaint(HWND hWnd, WPARAM wParam, LPARAM lParam)
{
std::vector<Gdiplus:oint> points;
std::vector<Gdiplus:oint>::iterator iter1, iter2;
HDC hdc, hdcMem;
HBITMAP hbmScreen, hbmOldBitmap;
PAINTSTRUCT ps;
RECT rect;

hdc = BeginPaint(hWnd, &ps);

//Create memory dc
hdcMem = CreateCompatibleDC(hdc);
GetClientRect(hWnd, &rect);
hbmScreen = CreateCompatibleBitmap(hdc, rect.right, rect.bottom);
hbmOldBitmap = (HBITMAP)SelectObject(hdcMem, hbmScreen);

//Fill the rect with white
FillRect(hdcMem, &rect, (HBRUSH)GetStockObject(WHITE_BRUSH));

//Draw the lines
Gdiplus::Graphics graphics(hdcMem);
Gdiplus:en blackPen(Gdiplus::Color(255, 0, 0));

points = m_pPolyLine->GetPoints();
for (iter1 = points.begin(); iter1 != points.end(); iter1++) {
for (iter2 = iter1 + 1; iter2 != points.end(); iter2++)
graphics.DrawLine(&blackPen, *iter1, *iter2);
}

//Copy the bitmap from memory dc to the real dc
BitBlt(hdc, 0, 0, rect.right, rect.bottom, hdcMem, 0, 0, SRCCOPY);

//Clean up
SelectObject(hdcMem, hbmOldBitmap);
DeleteObject(hbmScreen);
DeleteDC(hdcMem);

EndPaint(hWnd, &ps);
return 0;
}
[/code]
<br/>
<br/>
However, if the size of points exceed 20, the client rect just flicker. I think the reason is that Gdiplus:rawLines is too slow.
<br/>
<br/>
Is there any method to solve the flicker problem? <br/>
Thanks.<br/>

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