Thread: A GDI question that is perhaps deeper than I think...

So here is the story: I am creating a tetris clone. And I have a a 2-d int array that holds the whole board in terms of a number 0-7, 0 for nothing there, and 1-7 cooresponding to the color of square. (each of the 7 tetris piece types has its own color).

Now I have a function called "RefreshBoard" that re outputs everything on the board from this array. Here is that function:
hbmSquare is a HBITMAP array that holds in each cell an HBITMAP object for each of the 7 colors. Everything else should be self-explanatory.

The problem I am having is something to do with this function, I am asking some of you experienced windows programmers to just look at this function and tell me if you see something innately wrong with it. The problem I have having is pretty much that BitBlt is in fact failing. The message box that goes off when it fails is poping up. I can't explain why this is, and so I will just ask you to tell me if you see something wrong with it, and I'll go from there. Here is this function:

Code:

void Board::RefreshBoard(Piece* currentPiece)
{
   HDC hdcMemory2;
   hdcMemory2 = CreateCompatibleDC(hdc);
   HBITMAP hbmCurrentSq;
   bool check;
    for(int y=0; y<20; y++)
    {
        for(int x=0; x<10; x++)
        {
            if(theBoard[x][y] > 0) // if the square is not blank
            {
                hbmCurrentSq = hbmSquare[theBoard[x][y]-1];
                SelectObject(hdcMemory2, hbmCurrentSq);
                check = BitBlt(hdc, x*17, y*17, 17, 17, hdcMemory2, 0, 0, SRCCOPY);
                 if (!check)
                 {
                     HWND hwnd;
                     MessageBox(hwnd, "BitBlt Fails!", "C baby", MB_OK | MB_ICONEXCLAMATION);
                 }
            }
            else if(theBoard[x][y] == 0)
               currentPiece->RemoveOnePiece(x,y);
        }
    }   
   DeleteDC(hdcMemory2);
}

I appreciate your help! Keep in mind, this isn't throwing any compiler errors, the error is in the workings of the function, not its syntax.

Nimit

Make sure when you select something into a DC you save the old object and select it back in when you are finished. That having been said, lets continue. You're really not doing to much error checking. How about throwing some checks for the main hdc and the bitmap before you select it into the DC. I think maybe you are selecting an invalid bitmap into the DC. If you want more help, you can e-mail me or post the project here and I can dig around in there further. Hope that helps.