[RESOLVED] Double Buffer (CreateCompatibleDC) black/white screen flashing

I am trying to avoid screen blinking...How do you handle WM_ERASEBKGND message?

Indeed, if you don't handle the erase background (turning into a 'do nothing'), then turn your attention erasing the bitmap when appropriate, you WILL have flicker (really bad flicker).

Screen is not flickering anymore, trouble is it remains black instead of being white.

it is because your memory DC has a black bitmap in it.

to make it white:

LRESULT CALLBACK WndProc(HWND hwnd, UINT Msg, WPARAM wParam, LPARAM lParam)
{
HDC hDC;

switch (Msg)
{
case WM_DESTROY :

PostQuitMessage(WM_QUIT);
break;

case WM_ERASEBKGND:
RECT rt;
GetUpdateRect(hwnd, &rt, FALSE);
hDC=GetDC(hwnd);
FillRect(hDC, &rt, (HBRUSH)CreateSolidBrush(RGB(255, 255, 255)));
ReleaseDC(hwnd, hDC);
break;

case WM_PAINT :
{
PAINTSTRUCT ps;
hDC = BeginPaint(hwnd, &ps);

HDC memoryHDC = CreateCompatibleDC(hDC);
HBITMAP hMemoryBmp = CreateCompatibleBitmap(hDC, 700, 700);
HBITMAP hOldBmp = (HBITMAP)SelectObject(memoryHDC, hMemoryBmp);

// Create Bitmap Structure to fill the background of that window
LPBITMAPINFO lpbi = (LPBITMAPINFO)new BYTE[sizeof(BITMAPINFOHEADER)];
lpbi->bmiHeader.biBitCount = 32;
lpbi->bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
lpbi->bmiHeader.biWidth = 700;
lpbi->bmiHeader.biHeight = 700;
lpbi->bmiHeader.biPlanes = 1;
lpbi->bmiHeader.biCompression = BI_RGB;
lpbi->bmiHeader.biSizeImage = 0;
lpbi->bmiHeader.biXPelsPerMeter = 0;
lpbi->bmiHeader.biYPelsPerMeter = 0;
lpbi->bmiHeader.biClrUsed = 0;
lpbi->bmiHeader.biClrImportant = 0;
// Create Bit Array for the Bitmap
BYTE *bArray = new BYTE[4*700*700];
for(int i=0; i<700*700; i++)
{
bArray[(4*i)+0] = 0xff; //blue
bArray[(4*i)+1] = 0xff; //green
bArray[(4*i)+2] = 0xff; //red
bArray[(4*i)+3] = 0x00; //junk
}
// Set Bitmap Bits in Memory DC
SetDIBits(memoryHDC, hMemoryBmp, 0, 700, bArray, lpbi, DIB_RGB_COLORS);
delete[] lpbi;
delete[] bArray;

//DRAW STUFF ON MEMORY DC HERE

BitBlt(hDC, 0, 0, 700, 700, memoryHDC, 0, 0, SRCCOPY);

SelectObject(memoryHDC, hOldBmp);
DeleteObject(hMemoryBmp);
DeleteDC(memoryHDC);

EndPaint(hwnd, &ps);
}
break;

}

DeleteObject(hDC);
return DefWindowProc(hwnd, Msg, wParam, lParam);
}

Just a point to make...it may work now but.....

In all double buffering technique, the background erase should do nothing.

You're erasing the background in the example you posted, which is being erased so quickly at the moment that you don't see it, but you probably will when drawing becomes more complicated.

Part of the elimination of flicker is the elimination of the background erase, relying on the fact that the bitmap is a complete replacement of the viewing area, obviating the need for an on screen erasure.

(You erase the bitmap surface instead, as required - and in the PAINT cycle (or other bitmap drawing cycle), not in the background message response).

Just a point to make...it may work now but.....

In all double buffering technique, the background erase should do nothing.

You're erasing the background in the example you posted, which is being erased so quickly at the moment that you don't see it, but you probably will when drawing becomes more complicated.

Part of the elimination of flicker is the elimination of the background erase, relying on the fact that the bitmap is a complete replacement of the viewing area, obviating the need for an on screen erasure.

(You erase the bitmap surface instead, as required - and in the PAINT cycle (or other bitmap drawing cycle), not in the background message response).

if I don't handle WM_ERASEBKGND screen is flickering significantly. So how to avoid the future problems ?

You respond to the erase background, with the case like you've done, but you don't actually erase anything.