Setting Landscape Mode in an MFC Application Written in C++

Introduction

Visual Studio will create a starter program based on the MFC Library. In that starter program, there will be three menu items for printing something in the application. I wanted the printed output to be in Landscape mode. So I looked high and low for a solution to this issue. Several sites on the internet gave various solutions for this issue and I tried some of them. Some things seemed to work and some did not. However, all the research did finally lead to a comprehensive solution.

MFC provides many convenient features for managing the Windows environment. It also hides many significant features of the environment. For example, there is a object of class DEVMODE buried in an application. It does not always exist, but is created on the fly when needed. In the DEVMODE object are two variables of interest with respect to the orientation of the printed output. They are:

• dmOrientation
• dmFields

dmOrientation may be set to one of two values: DMORIENT_PORTRAIT and DMORIENT_LANDSCAPE. dmFields contains a bit for a number of fields in the object. The bit that specifies dmOrientation contains data is DM_ORIENTATION.

There are three printing functions supplied by Visual Studio:

1. Print
2. Print Preview
3. Print Setup

My goal was to have each of these functions default to Landscape Orientation. It turned out that two functions would accomplish that goal although they need to be called at different times in the execution of each function. But first, let me describe the two functions.

Get a DEVMODE Handle

The DEVMODE object, when it exists, is managed by CWinApp. When Visual Studio creates an application, it creates a class with the name of the Application that is a sub-class of CWinApp (or its big brother CWinAppEx). The function getDevMode() returns a handle to a DEVMODE object suitable for modification of the Printer Orientation. The application class declaration in the MyApp.h file may look like the following:

class MyApp : public CWinAppEx {

  o o o

  HANDLE     getDevMode() {return m_hDevMode ? m_hDevMode : defDevMode();}

private:

  HANDLE    defDevMode();
  };

The body (the MyApp.cpp file) of the application class should contain the private function:

HANDLE MyApp::defDevMode() {
PRINTDLG pd;

  pd.lStructSize = (DWORD) sizeof(PRINTDLG);

  return GetPrinterDeviceDefaults(&pd) ? pd.hDevMode : 0;
  }

The logic of these functions is as follows:

If a member variable of CWinApp is non-zero, it is a handle of the DEVMODE object, otherwise get the printer defaults and return the handle of the default DEVMODE object.

In my experience, one of the two works. Of course, if the Get Defaults function fails then returns 0, i.e., complete failure. By the way, this functionality is always available anywhere in the application due to the availability of "theApp". The call is theApp.getDevMode();

Setting the Orientation Mode

Clearly having a handle is not enough, the actual object must be available for modification. Here is that sequence of code. I put the code in the View class. The header file (i.e., MyAppView.h) of the View class would contain the following:

bool setPrntrOrient(HANDLE h, CDC* dc = 0);

The body (i.e., MyAppView.cpp) of the view class would contain:

bool MyAppView::setPrntrOrient(HANDLE h, CDC* dc) {
DEVMODE* devMode;

  if (!h) return false;

  devMode = (DEVMODE*)::GlobalLock(h);    if (!devMode) return false;

  switch (orient) {
    case Portrait : devMode->dmOrientation = DMORIENT_PORTRAIT;  // portrait mode
                    devMode->dmFields     |= DM_ORIENTATION; break;

    case Landscape: devMode->dmOrientation = DMORIENT_LANDSCAPE; // landscape mode
                    devMode->dmFields     |= DM_ORIENTATION; break;
    }

  if (dc) dc->ResetDC(devMode);

  ::GlobalUnlock(h); return true;
  }

Many places in the internet showed the GlobalLock and changing of the dmOrientation parameter. A little later, I'll touch on the reason for this article, just bear with me please.

The switch variable is an enum object defined in the View class so that only one call need be made to setup the mode. It could just as easily be an argument of the function.

This function is really ignorant of the source of the handle for the DEVMODE object. That is a good thing as it will then function with both the Print Setup and Print functions.

Modification of the Print Menu Functions

A successful changing of the Orietation of the printer setup and output is accomplished with two calls:

   view()->setOrientation(Landscape);                    // Sets the orient variable 
                                                         // in the View object
   view()->setPrntrOrient(theApp.getDevMode(), dc);      // Or dc allowed to be zero

Print Setup

Print Setup is always a command in the application class (e.g., MyApp). There is a command listed in the Message Map (search for BEGIN_MESSAGE_MAP):

ON_COMMAND(ID_FILE_PRINT_SETUP, &CWinApp::OnPrinterSetup)

One needs to replace that pointer with one to a MyApp function:

ON_COMMAND(ID_FILE_PRINT_SETUP, &MyApp::OnPrinterSetup) // The only change is "MyApp"

Then the MyApp version of OnPrinterSetup is:

void MyApp::OnPrinterSetup()
{view()->setPrntrOrient(getDevMode());   CWinApp::OnFilePrintSetup();}

In this case, the application object the handle for DEVMODE is zero so the getDevMode function returns the default DEVMODE object which is then set and OnFilePrintSetup displays landscape as the default orientation.

Print and Print Preview

Print and Print Preview seem to be slighly more complex. When Printing is started, several virtual functions are called one after another. One of the first such functions is OnBeginPrinting. In the MyAppView header file (MyAppView.h), add the following line in the public part of the view class:

virtual void OnBeginPrinting(CDC* pDC, CPrintInfo* pInfo);

In the MyAppView body file (MyAppView.cpp), add the function:

void MyAppView::OnBeginPrinting(CDC* pDC, CPrintInfo* pInfo) {

  setPrntrOrient(theApp.getDevMode(), pDC);

  CScrollView::OnBeginPrinting(pDC, pInfo);     // or CView::
  }

In this instance, the printing function has begun and the application object (i.e., theApp) contains the handle for the DEVMODE object and getDevMode returns it. Then setPrntrOrient changes it according to the View variable orient which has been set previously.

This work was done with Visual Studio 2017 in Windows 7. I did not explore several other ways to use these two functions as this was sufficient for my purposes.

History

• 8^th August, 2020: Initial version