SetDIBits fails on WM_PAINT when trying to draw - c++

Question

I am trying to draw plot using matrix, where each element is DWORD value, that represent pixel ARGB value. Idea behind the application is that one separate thread do the calculation (mat. formula), whose result will be the matrix with ARGB values. When WM_PAINT is raised I will use function to draw, using the filled matrix:
void DrawImage( HDC hDC, WORD wWidth, WORD wHeight )
{
HBITMAP hBitmap;
HDC hMemDC;
BITMAPINFO bi;
int iSize = sizeof( BITMAPINFO );
memcpy( &bi, dwBytes + 3, iSize);
hBitmap = CreateCompatibleBitmap(hDC, wWidth, wHeight);
hMemDC = CreateCompatibleDC( hDC );
if ( 0 == SetDIBits( hDC, hBitmap, 0,
wHeight, dwBytes, &bi, DIB_RGB_COLORS ) )
{
// error MSDN http://msdn.microsoft.com/en-us/library/
//windows/desktop/dd162973%28v=vs.85%29.aspx
}
hBitmap = (HBITMAP) SelectObject(hMemDC, hBitmap);
BitBlt(hDC, 0, 0, wWidth, wHeight, hMemDC, 0, 0, SRCCOPY);
DeleteObject(SelectObject(hMemDC, hBitmap));
DeleteDC(hMemDC);
}
so, when WM_PAINT is raised:
case WM_PAINT:
{
PAINTSTRUCT ps = { 0 };
HDC hDC = BeginPaint( hWnd, &ps );
DrawImage( hDC, iWidth, iHeight );
EndPaint( hWnd, &ps );
return 0L;
}
but nothing happens. The area is black. When SetDIBits returns 0 it means that "One or more of the input parameters is invalid" according to MSDN. I am out of ideas..

Answer 1

sizeof( BITMAPINFO ) includes only 1 pixel. BITMAPINFO is a variable-length structure so you need to compute its size dynamically and allocate sufficient memory dynamically.

Answer 2

You pointed me to investigate handling BITMAPINFO structure, and there it was. After I have changed one plane, 32 bits per pixel and width 800 and height 600 - it worked!
void DrawImage( HDC hDC, WORD wWidth, WORD wHeight )
{
HDC hMemDC;
BITMAPINFO bmi;
ZeroMemory(&bmi, sizeof(BITMAPINFO));
bmi.bmiHeader.biSize = sizeof(BITMAPINFOHEADER);
bmi.bmiHeader.biBitCount = 32;
bmi.bmiHeader.biHeight = 600;
bmi.bmiHeader.biWidth = 800;
bmi.bmiHeader.biPlanes = 1;
hMemDC = CreateCompatibleDC( hDC );
HBITMAP hBitmap = CreateDIBSection( hMemDC, &bmi, DIB_RGB_COLORS,
(void**) &dwBytes, NULL, 0);
SetDIBits( hDC, hBitmap, 0, wHeight, dwBytes, &bmi, DIB_RGB_COLORS );
HBITMAP hOldBitmap = (HBITMAP) SelectObject( hMemDC, hBitmap );
BitBlt(hDC, 0, 0, wWidth, wHeight, hMemDC, 0, 0, SRCCOPY);
SelectObject( hMemDC, hBitmap );
DeleteObject( hBitmap );
DeleteDC(hMemDC);
}
I got proper result: