Set GDI page settings for printing C++ - c++

Question

I am having trouble setting the "default" page size for my document. I am using Visual C++ on Windows, with GDI calls (required for backward-compatibility).
So far my basic approach is to get a default DEVMODE, set the properties on it that I want, and then prompt the user if he wants to change it. But it seems to make no difference on the page size. It works on Orientation.
What am I doing wrong?
HDC GetPrinterDC () {
// Initialize device
PRINTDLG pd = {0};
pd.lStructSize = sizeof( pd );
pd.Flags = PD_RETURNDEFAULT;
PrintDlg(&pd);
// If device initialization failed, abort
if (pd.hDevMode == NULL) return NULL;
// Get the actual memory pointer
PDEVMODE dm = (PDEVMODE)GlobalLock(pd.hDevMode);
if (dm) {
// Set any properties that are specific for our document
if (dm->dmFields & DM_ORIENTATION)
dm->dmOrientation = DMORIENT_LANDSCAPE;
if (dm->dmFields & DM_PAPERSIZE)
dm->dmPaperSize = 0;
if (dm->dmFields & DM_PAPERLENGTH)
dm->dmPaperLength = 3302; // 13in
if (dm->dmFields & DM_PAPERWIDTH)
dm->dmPaperWidth = 4572; // 18in
GlobalUnlock(pd.hDevMode);
}
// Initialize a PRINTDLG structure.
pd.hwndOwner = GetForegroundWindow();
pd.Flags = PD_RETURNDC | PD_HIDEPRINTTOFILE | PD_DISABLEPRINTTOFILE | PD_NOPAGENUMS | PD_NOSELECTION | PD_USEDEVMODECOPIESANDCOLLATE ;
// Retrieve the printer DC
HDC hdc = NULL;
if (PrintDlg(&pd)) hdc = pd.hDC;
// Free the resources allocated
if (pd.hDevMode != NULL) GlobalFree(pd.hDevMode);
if (pd.hDevNames != NULL) GlobalFree(pd.hDevNames);
return hdc;
}

Answer 1

Apparently you can specify dmFields in the DEVMODE struct to be anything you want.
The code should look like this:
PDEVMODE dm = (PDEVMODE)GlobalLock(pd.hDevMode);
if (dm) {
// Set any properties that are specific for our document
dm->dmFields = dm->dmFields | DM_ORIENTATION | DM_PAPERSIZE
| DM_PAPERLENGTH | DM_PAPERWIDTH;
dm->dmOrientation = DMORIENT_LANDSCAPE;
dm->dmPaperSize = 0;
dm->dmPaperLength = 3302; // 13in
dm->dmPaperWidth = 4572; // 18in
GlobalUnlock(pd.hDevMode);
}