HP printer & WINGDI - page size - windows

Question

I have to use GDI to print documents with printers in general.I can get the device no problem. I also communicate it desired page size like:
HANDLE hPrinter;
OpenPrinterW( printerName, &hPrinter, 0 );
DocumentPropertiesW( 0, hPrinter, printerName,
pDevMode, NULL, DM_OUT_BUFFER);
if( settings.paperLength > 0 && settings.paperWidth > 0 )
{
if( pDevMode->dmFields & DM_PAPERSIZE )
{
pDevMode->dmPaperSize = 0;
}
if( pDevMode->dmFields & DM_PAPERLENGTH )
{
pDevMode->dmPaperLength = settings.paperLength;
}
if( pDevMode->dmFields & DM_PAPERWIDTH )
{
pDevMode->dmPaperWidth = settings.paperWidth;
}
}
DocumentPropertiesW( 0, hPrinter, printerName, 0, pDevMode,
DM_IN_BUFFER | DM_OUT_BUFFER );
ClosePrinter( hPrinter );
Then I StretchBlt my document and print it.
DOCINFOW di;
memset ((void *) &di, 0, sizeof (di));
di.cbSize = sizeof (DOCINFOW);
di.lpszDocName = utf_to_widechar("Document").data();
HDC hdc = this->deviceContext;
auto cxpage = GetDeviceCaps( hdc, HORZRES );
auto cypage = GetDeviceCaps( hdc, VERTRES );
auto hdcMem = CreateCompatibleDC( hdc );
BITMAPINFO bi;
bi.bmiHeader = {sizeof(bi.bmiHeader), settings.width, settings.height,
1, 24, BI_RGB, 0, 0x0ec4, 0x0ec4, 0, 0};
LPVOID ppvBits;
auto hBitmap = CreateDIBSection( 0, &bi, DIB_RGB_COLORS, &ppvBits, 0, 0 );
auto hbmOld = SelectObject( hdcMem, hBitmap );
StartDocW( hdc, &di);
for(int i = 0; i < this->colorTables.size(); ++i)
{
int size = settings.width * settings.height * 3;
StartPage( hdc );
SetDIBits( 0, hBitmap, 0, settings.height,
(PVOID)&(colorTables[i][0]), &bi, DIB_RGB_COLORS );
SetMapMode( hdc, MM_ISOTROPIC )
SetWindowExtEx( hdc, cxpage, cypage, 0 );
SetViewportExtEx( hdc, cxpage, cypage, 0 );
SetViewportOrgEx( hdc, 0, 0, 0 );
StretchBlt( hdc, 0, 0, cxpage, cypage, hdcMem, 0, 0,
settings.width, settings.height, SRCCOPY );
EndPage( hdc );
}
EndDoc( hdc );
SelectObject( hdcMem, hbmOld );
DeleteDC( hdcMem );
Now, my document is 210mmx99mm. Most printers more or less properly handle this: the print size is proper, and either is it located left top corner, or top in the middle, if a printer supports smaller paper sizes. The issue is, I am working with HP printer now and it just doesn't work this way. The print is stretched all over A4 [which means that it is resized to cover whole A4 page, which is both wrong size and wrong proportions]. I know the printer can actually do it. I can use other software to print such documents properly. It just seems HP doesn't fully support some GDI functions. Is there some way to sort it out?