PrintDlgEx fails with "Invalid Argument" - c

Question

I am Working with Win32 API and C.
I need to get supported page sizes of my system default printer.
Referring to DeviceCapabilities of a network printer on this forum (which suggested PrintDlg), I am trying to use PrintDlgEx, with Flags=PD_RETURNDEFAULT.
My problem is, call to PrintDlgEx fails with error "E_INVALIDARG", ie, Invalid Argument.
I have written the code as a console program.
Can some one help me identify what is going wrong.
My code is pasted below
int main(void)
{
HWND Myhwnd = GetConsoleWindow();
if (Myhwnd == NULL)
printf("GetConsoleWindow Failed \n");
PRINTDLGEX pdlg;
memset(&pdlg, 0, sizeof(PRINTDLGEX));
pdlg.lStructSize = sizeof(PRINTDLGEX);
pdlg.hwndOwner = Myhwnd;
pdlg.Flags = PD_RETURNDEFAULT|| PD_NOPAGENUMS;
pdlg.nCopies = 1;
pdlg.nPropertyPages = 0;
pdlg.dwResultAction = 0;
pdlg.nStartPage = START_PAGE_GENERAL;
HRESULT result = PrintDlgEx(&pdlg);
switch (result)
{
... ...
case E_INVALIDARG:
printf("Invalid Argument\n");
break;
}
return 0;
}
I noticed in PrintDlgEx documentation it says "This structure must be declared dynamically using a memory allocation function.". So I changed my program as below, but still gives same error "Invalid Argument".
int main(void)
{
HWND Myhwnd = GetConsoleWindow();
if (Myhwnd == NULL)
printf("GetConsoleWindow Failed \n");
PRINTDLGEX * pdlg;
pdlg = malloc(sizeof(PRINTDLGEX));
memset(pdlg, 0, sizeof(PRINTDLGEX));
pdlg->lStructSize = sizeof(PRINTDLGEX);
pdlg->hwndOwner = Myhwnd;
pdlg->Flags = PD_RETURNDEFAULT|| PD_NOPAGENUMS;
pdlg->nCopies = 1;
pdlg->nPropertyPages = 0;
pdlg->dwResultAction = 0;
pdlg->nStartPage = START_PAGE_GENERAL;
HRESULT result = PrintDlgEx(pdlg);
switch (result)
{
... ...
case E_INVALIDARG:
printf("Invalid Argument\n");
break;
}
return 0;
}

Answer 1

I have checked your code with MSVC2019. As IInspectable said in a comment, the error is the use of boolean or || operator instead of bitwise or |operator.
I also checked that the call work with a statically allocated PRINTDLGEX variable or a dynamically allocated one.
The code is:
#include <stdio.h>
#include <stdlib.h>
#include <windows.h>
int main(void)
{
HWND Myhwnd = GetConsoleWindow();
if (Myhwnd == NULL)
printf("GetConsoleWindow Failed \n");
PRINTDLGEX pdlg;
memset(&pdlg, 0, sizeof(PRINTDLGEX));
pdlg.lStructSize = sizeof(PRINTDLGEX);
pdlg.hwndOwner = Myhwnd;
pdlg.Flags = PD_RETURNDEFAULT | PD_NOPAGENUMS;
pdlg.nCopies = 1;
pdlg.nPropertyPages = 0;
pdlg.dwResultAction = 0;
pdlg.nStartPage = START_PAGE_GENERAL;
HRESULT result = PrintDlgEx(&pdlg);
switch (result)
{
case S_OK:
printf("Success\n");
break;
case E_INVALIDARG:
printf("Invalid Argument\n");
break;
default:
printf("Error %d\n", result);
break;
}
return 0;
}