wxWidgets/samples/printing/printing.cpp

/////////////////////////////////////////////////////////////////////////////
// Name:        samples/printing.cpp
// Purpose:     Printing demo for wxWidgets
// Author:      Julian Smart
// Modified by:
// Created:     1995
// RCS-ID:      $Id$
// Copyright:   (c) Julian Smart
// Licence:     wxWindows licence
/////////////////////////////////////////////////////////////////////////////

// For compilers that support precompilation, includes "wx/wx.h".
#include "wx/wxprec.h"

#ifdef __BORLANDC__
#pragma hdrstop
#endif

#ifndef WX_PRECOMP
#include "wx/wx.h"
#endif

#if !wxUSE_PRINTING_ARCHITECTURE
#error "You must set wxUSE_PRINTING_ARCHITECTURE to 1 in setup.h, and recompile the library."
#endif

// Set this to 1 if you want to test PostScript printing under MSW.
// However, you'll also need to edit src/msw/makefile.nt.
#define wxTEST_POSTSCRIPT_IN_MSW 0

#include <ctype.h>
#include "wx/metafile.h"
#include "wx/print.h"
#include "wx/printdlg.h"
#include "wx/image.h"
#include "wx/accel.h"

#if wxTEST_POSTSCRIPT_IN_MSW
#include "wx/generic/printps.h"
#include "wx/generic/prntdlgg.h"
#endif

#ifdef __WXMAC__
#include "wx/mac/printdlg.h"
#endif

#include "printing.h"

#ifndef __WXMSW__
#include "mondrian.xpm"
#endif

#if wxUSE_LIBGNOMEPRINT
#include "wx/html/forcelnk.h"
FORCE_LINK(gnome_print)
#endif


// Declare a frame
MyFrame   *frame = (MyFrame *) NULL;
// int orientation = wxPORTRAIT;

// Global print data, to remember settings during the session
wxPrintData *g_printData = (wxPrintData*) NULL ;

// Global page setup data
wxPageSetupDialogData* g_pageSetupData = (wxPageSetupDialogData*) NULL;

// Main proc
IMPLEMENT_APP(MyApp)

// Writes a header on a page. Margin units are in millimetres.
bool WritePageHeader(wxPrintout *printout, wxDC *dc, const wxChar *text, float mmToLogical);

// The `main program' equivalent, creating the windows and returning the
// main frame

bool MyApp::OnInit(void)
{
    if ( !wxApp::OnInit() )
        return false;

    wxInitAllImageHandlers();

    m_testFont.Create(10, wxSWISS, wxNORMAL, wxNORMAL);

    g_printData = new wxPrintData;
    // You could set an initial paper size here
//    g_printData->SetPaperId(wxPAPER_LETTER); // for Americans
//    g_printData->SetPaperId(wxPAPER_A4);    // for everyone else    

    g_pageSetupData = new wxPageSetupDialogData;
    // copy over initial paper size from print record
    (*g_pageSetupData) = *g_printData;
    // Set some initial page margins in mm. 
    g_pageSetupData->SetMarginTopLeft(wxPoint(15, 15));
    g_pageSetupData->SetMarginBottomRight(wxPoint(15, 15));

    // Create the main frame window
    frame = new MyFrame((wxFrame *) NULL, _T("wxWidgets Printing Demo"), 
        wxPoint(0, 0), wxSize(400, 400));

#if wxUSE_STATUSBAR
    // Give it a status line
    frame->CreateStatusBar(2);
#endif // wxUSE_STATUSBAR

    // Load icon and bitmap
    frame->SetIcon( wxICON( mondrian) );

    // Make a menubar
    wxMenu *file_menu = new wxMenu;

    file_menu->Append(WXPRINT_PRINT, _T("&Print..."),              _T("Print"));
    file_menu->Append(WXPRINT_PAGE_SETUP, _T("Page Set&up..."),              _T("Page setup"));
#ifdef __WXMAC__
    file_menu->Append(WXPRINT_PAGE_MARGINS, _T("Page Margins..."), _T("Page margins"));
#endif
    file_menu->Append(WXPRINT_PREVIEW, _T("Print Pre&view"),              _T("Preview"));

#if wxUSE_ACCEL
    // Accelerators
    wxAcceleratorEntry entries[1];
    entries[0].Set(wxACCEL_CTRL, (int) 'V', WXPRINT_PREVIEW);
    wxAcceleratorTable accel(1, entries);
    frame->SetAcceleratorTable(accel);
#endif

#if defined(__WXMSW__) && wxTEST_POSTSCRIPT_IN_MSW
    file_menu->AppendSeparator();
    file_menu->Append(WXPRINT_PRINT_PS, _T("Print PostScript..."),              _T("Print (PostScript)"));
    file_menu->Append(WXPRINT_PAGE_SETUP_PS, _T("Page Setup PostScript..."),              _T("Page setup (PostScript)"));
    file_menu->Append(WXPRINT_PREVIEW_PS, _T("Print Preview PostScript"),              _T("Preview (PostScript)"));
#endif

    file_menu->AppendSeparator();
    file_menu->Append(WXPRINT_ANGLEUP, _T("Angle up\tAlt-U"),                _T("Raise rotated text angle"));
    file_menu->Append(WXPRINT_ANGLEDOWN, _T("Angle down\tAlt-D"),            _T("Lower rotated text angle"));
    file_menu->AppendSeparator();
    file_menu->Append(WXPRINT_QUIT, _T("E&xit"),                _T("Exit program"));

    wxMenu *help_menu = new wxMenu;
    help_menu->Append(WXPRINT_ABOUT, _T("&About"),              _T("About this demo"));

    wxMenuBar *menu_bar = new wxMenuBar;

    menu_bar->Append(file_menu, _T("&File"));
    menu_bar->Append(help_menu, _T("&Help"));

    // Associate the menu bar with the frame
    frame->SetMenuBar(menu_bar);

    MyCanvas *canvas = new MyCanvas(frame, wxPoint(0, 0), wxSize(100, 100), wxRETAINED|wxHSCROLL|wxVSCROLL);

    // Give it scrollbars: the virtual canvas is 20 * 50 = 1000 pixels in each direction
    canvas->SetScrollbars(20, 20, 50, 50);

    frame->canvas = canvas;

    frame->Centre(wxBOTH);
    frame->Show();

#if wxUSE_STATUSBAR
    frame->SetStatusText(_T("Printing demo"));
#endif // wxUSE_STATUSBAR

    SetTopWindow(frame);

    return true;
}

int MyApp::OnExit()
{
    delete g_printData;
    delete g_pageSetupData;
    return 1;
}

BEGIN_EVENT_TABLE(MyFrame, wxFrame)
EVT_MENU(WXPRINT_QUIT, MyFrame::OnExit)
EVT_MENU(WXPRINT_PRINT, MyFrame::OnPrint)
EVT_MENU(WXPRINT_PREVIEW, MyFrame::OnPrintPreview)
EVT_MENU(WXPRINT_PAGE_SETUP, MyFrame::OnPageSetup)
EVT_MENU(WXPRINT_ABOUT, MyFrame::OnPrintAbout)
#if defined(__WXMSW__) && wxTEST_POSTSCRIPT_IN_MSW
EVT_MENU(WXPRINT_PRINT_PS, MyFrame::OnPrintPS)
EVT_MENU(WXPRINT_PREVIEW_PS, MyFrame::OnPrintPreviewPS)
EVT_MENU(WXPRINT_PAGE_SETUP_PS, MyFrame::OnPageSetupPS)
#endif
#ifdef __WXMAC__
EVT_MENU(WXPRINT_PAGE_MARGINS, MyFrame::OnPageMargins)
#endif
EVT_MENU(WXPRINT_ANGLEUP, MyFrame::OnAngleUp)
EVT_MENU(WXPRINT_ANGLEDOWN, MyFrame::OnAngleDown)
END_EVENT_TABLE()

// Define my frame constructor
MyFrame::MyFrame(wxFrame *frame, const wxString& title, const wxPoint& pos, const wxSize& size):
wxFrame(frame, wxID_ANY, title, pos, size)
{
    canvas = NULL;
    m_angle = 30;
#if 0
    wxImage image( wxT("test.jpg") );
    image.SetAlpha();
    int i,j;
    for (i = 0; i < image.GetWidth(); i++)
       for (j = 0; j < image.GetHeight(); j++)
          image.SetAlpha( i, j, 50 );
    m_bitmap = image;
#endif
}

void MyFrame::OnExit(wxCommandEvent& WXUNUSED(event))
{
    Close(true /*force closing*/);
}

void MyFrame::OnPrint(wxCommandEvent& WXUNUSED(event))
{
    wxPrintDialogData printDialogData(* g_printData);

    wxPrinter printer(& printDialogData);
    MyPrintout printout(_T("My printout"));
    if (!printer.Print(this, &printout, true /*prompt*/))
    {
        if (wxPrinter::GetLastError() == wxPRINTER_ERROR)
            wxMessageBox(_T("There was a problem printing.\nPerhaps your current printer is not set correctly?"), _T("Printing"), wxOK);
        else
            wxMessageBox(_T("You canceled printing"), _T("Printing"), wxOK);
    }
    else
    {
        (*g_printData) = printer.GetPrintDialogData().GetPrintData();
    }
}

void MyFrame::OnPrintPreview(wxCommandEvent& WXUNUSED(event))
{
    // Pass two printout objects: for preview, and possible printing.
    wxPrintDialogData printDialogData(* g_printData);
    wxPrintPreview *preview = new wxPrintPreview(new MyPrintout, new MyPrintout, & printDialogData);
    if (!preview->Ok())
    {
        delete preview;
        wxMessageBox(_T("There was a problem previewing.\nPerhaps your current printer is not set correctly?"), _T("Previewing"), wxOK);
        return;
    }

    wxPreviewFrame *frame = new wxPreviewFrame(preview, this, _T("Demo Print Preview"), wxPoint(100, 100), wxSize(600, 650));
    frame->Centre(wxBOTH);
    frame->Initialize();
    frame->Show();
}

void MyFrame::OnPageSetup(wxCommandEvent& WXUNUSED(event))
{
    (*g_pageSetupData) = *g_printData;

    wxPageSetupDialog pageSetupDialog(this, g_pageSetupData);
    pageSetupDialog.ShowModal();

    (*g_printData) = pageSetupDialog.GetPageSetupDialogData().GetPrintData();
    (*g_pageSetupData) = pageSetupDialog.GetPageSetupDialogData();
}

#if defined(__WXMSW__) && wxTEST_POSTSCRIPT_IN_MSW
void MyFrame::OnPrintPS(wxCommandEvent& WXUNUSED(event))
{
    wxPostScriptPrinter printer(g_printData);
    MyPrintout printout(_T("My printout"));
    printer.Print(this, &printout, true/*prompt*/);

    (*g_printData) = printer.GetPrintData();
}

void MyFrame::OnPrintPreviewPS(wxCommandEvent& WXUNUSED(event))
{
    // Pass two printout objects: for preview, and possible printing.
    wxPrintDialogData printDialogData(* g_printData);
    wxPrintPreview *preview = new wxPrintPreview(new MyPrintout, new MyPrintout, & printDialogData);
    wxPreviewFrame *frame = new wxPreviewFrame(preview, this, _T("Demo Print Preview"), wxPoint(100, 100), wxSize(600, 650));
    frame->Centre(wxBOTH);
    frame->Initialize();
    frame->Show();
}

void MyFrame::OnPageSetupPS(wxCommandEvent& WXUNUSED(event))
{
    (*g_pageSetupData) = * g_printData;

    wxGenericPageSetupDialog pageSetupDialog(this, g_pageSetupData);
    pageSetupDialog.ShowModal();

    (*g_printData) = pageSetupDialog.GetPageSetupDialogData().GetPrintData();
    (*g_pageSetupData) = pageSetupDialog.GetPageSetupDialogData();
}
#endif


#ifdef __WXMAC__
void MyFrame::OnPageMargins(wxCommandEvent& WXUNUSED(event))
{
    (*g_pageSetupData) = *g_printData;

    wxMacPageMarginsDialog pageMarginsDialog(this, g_pageSetupData);
    pageMarginsDialog.ShowModal();

    (*g_printData) = pageMarginsDialog.GetPageSetupDialogData().GetPrintData();
    (*g_pageSetupData) = pageMarginsDialog.GetPageSetupDialogData();
}
#endif


void MyFrame::OnPrintAbout(wxCommandEvent& WXUNUSED(event))
{
    (void)wxMessageBox(_T("wxWidgets printing demo\nAuthor: Julian Smart"),
        _T("About wxWidgets printing demo"), wxOK|wxCENTRE);
}

void MyFrame::OnAngleUp(wxCommandEvent& WXUNUSED(event))
{
    m_angle += 5;
    canvas->Refresh();
}

void MyFrame::OnAngleDown(wxCommandEvent& WXUNUSED(event))
{
    m_angle -= 5;
    canvas->Refresh();
}

void MyFrame::Draw(wxDC& dc)
{
    // This routine just draws a bunch of random stuff on the screen so that we
    // can check that different types of object are being drawn consistently
    // between the screen image, the print preview image (at various zoom
    // levels), and the printed page.
    dc.SetBackground(*wxWHITE_BRUSH);
    dc.Clear();
    dc.SetFont(wxGetApp().m_testFont);

    dc.SetBackgroundMode(wxTRANSPARENT);

    dc.SetPen(*wxBLACK_PEN);
    dc.SetBrush(*wxLIGHT_GREY_BRUSH);
    dc.DrawRectangle(0, 0, 230, 350);
    dc.DrawLine(0, 0, 229, 349);
    dc.DrawLine(229, 0, 0, 349);
    dc.SetBrush(*wxTRANSPARENT_BRUSH);

    dc.SetBrush(*wxCYAN_BRUSH);
    dc.SetPen(*wxRED_PEN);

    dc.DrawRoundedRectangle(0, 20, 200, 80, 20);

    dc.DrawText( wxT("Rectangle 200 by 80"), 40, 40);

    dc.SetPen( wxPen(*wxBLACK,0,wxDOT_DASH) );
    dc.DrawEllipse(50, 140, 100, 50);
    dc.SetPen(*wxRED_PEN);

    dc.DrawText( wxT("Test message: this is in 10 point text"), 10, 180);
    
#if wxUSE_UNICODE
    char *test = "Hebrew    שלום -- Japanese (日本語)";
    wxString tmp = wxConvUTF8.cMB2WC( test );
    dc.DrawText( tmp, 10, 200 );
#endif

    wxPoint points[5];
    points[0].x = 0;
    points[0].y = 0;
    points[1].x = 20;
    points[1].y = 0;
    points[2].x = 20;
    points[2].y = 20;
    points[3].x = 10;
    points[3].y = 20;
    points[4].x = 10;
    points[4].y = -20;
    dc.DrawPolygon( 5, points, 20, 250, wxODDEVEN_RULE );
    dc.DrawPolygon( 5, points, 50, 250, wxWINDING_RULE );

    dc.DrawEllipticArc( 80, 250, 60, 30, 0.0, 270.0 );

    points[0].x = 150;
    points[0].y = 250;
    points[1].x = 180;
    points[1].y = 250;
    points[2].x = 180;
    points[2].y = 220;
    points[3].x = 200;
    points[3].y = 220;
    dc.DrawSpline( 4, points );

    dc.DrawArc( 20,10, 10,10, 25,40 );
        
    wxString str;
    int i = 0;
    str.Printf( wxT("---- Text at angle %d ----"), i );
    dc.DrawRotatedText( str, 100, 300, i );

    i = m_angle;
    str.Printf( wxT("---- Text at angle %d ----"), i );
    dc.DrawRotatedText( str, 100, 300, i );

    wxIcon my_icon = wxICON(mondrian) ;

    dc.DrawIcon( my_icon, 100, 100);

    if (m_bitmap.Ok())
        dc.DrawBitmap( m_bitmap, 10, 10 );
}

void MyFrame::OnSize(wxSizeEvent& event )
{
    wxFrame::OnSize(event);
}

BEGIN_EVENT_TABLE(MyCanvas, wxScrolledWindow)
EVT_MOUSE_EVENTS(MyCanvas::OnEvent)
END_EVENT_TABLE()

MyCanvas::MyCanvas(wxFrame *frame, const wxPoint& pos, const wxSize& size, long style):
    wxScrolledWindow(frame, wxID_ANY, pos, size, style)
{
    SetBackgroundColour(* wxWHITE);
}

void MyCanvas::OnDraw(wxDC& dc)
{
    frame->Draw(dc);
}

void MyCanvas::OnEvent(wxMouseEvent& WXUNUSED(event))
{
}

bool MyPrintout::OnPrintPage(int page)
{
    wxDC *dc = GetDC();
    if (dc)
    {
        if (page == 1)
            DrawPageOne();
        else if (page == 2)
            DrawPageTwo();

        // Draw page numbers at top left corner of printable area, sized so that
        // screen size of text matches paper size.
        MapScreenSizeToPage();
        wxChar buf[200];
        wxSprintf(buf, wxT("PAGE %d"), page);
        dc->DrawText(buf, 0, 0);

        return true;
    }
    else
        return false;
}

bool MyPrintout::OnBeginDocument(int startPage, int endPage)
{
    if (!wxPrintout::OnBeginDocument(startPage, endPage))
        return false;

    return true;
}

void MyPrintout::GetPageInfo(int *minPage, int *maxPage, int *selPageFrom, int *selPageTo)
{
    *minPage = 1;
    *maxPage = 2;
    *selPageFrom = 1;
    *selPageTo = 2;
}

bool MyPrintout::HasPage(int pageNum)
{
    return (pageNum == 1 || pageNum == 2);
}

void MyPrintout::DrawPageOne()
{
    // You might use THIS code if you were scaling graphics of known size to fit
    // on the page. The commented-out code illustrates different ways of scaling
    // the graphics.

    // We know the graphic is 230x350. If we didn't know this, we'd need to
    // calculate it.
    wxCoord maxX = 230;
    wxCoord maxY = 350;

    // This sets the user scale and origin of the DC so that the image fits
    // within the paper rectangle (but the edges could be cut off by printers
    // that can't print to the edges of the paper -- which is most of them. Use
    // this if your image already has its own margins.
//    FitThisSizeToPaper(wxSize(maxX, maxY));
//    wxRect fitRect = GetLogicalPaperRect();

    // This sets the user scale and origin of the DC so that the image fits
    // within the page rectangle, which is the printable area on Mac and MSW
    // and is the entire page on other platforms.
//    FitThisSizeToPage(wxSize(maxX, maxY));
//    wxRect fitRect = GetLogicalPageRect();

    // This sets the user scale and origin of the DC so that the image fits
    // within the page margins as specified by g_PageSetupData, which you can
    // change (on some platforms, at least) in the Page Setup dialog. Note that
    // on Mac, the native Page Setup dialog doesn't let you change the margins
    // of a wxPageSetupDialogData object, so you'll have to write your own dialog or
    // use the Mac-only wxMacPageMarginsDialog, as we do in this program.
    FitThisSizeToPageMargins(wxSize(maxX, maxY), *g_pageSetupData);
    wxRect fitRect = GetLogicalPageMarginsRect(*g_pageSetupData);

    // This sets the user scale and origin of the DC so that the image appears
    // on the paper at the same size that it appears on screen (i.e., 10-point
    // type on screen is 10-point on the printed page) and is positioned in the
    // top left corner of the page rectangle (just as the screen image appears
    // in the top left corner of the window).
//    MapScreenSizeToPage();
//    wxRect fitRect = GetLogicalPageRect();

    // You could also map the screen image to the entire paper at the same size
    // as it appears on screen.
//    MapScreenSizeToPaper();
//    wxRect fitRect = GetLogicalPaperRect();

    // You might also wish to do you own scaling in order to draw objects at
    // full native device resolution. In this case, you should do the following.
    // Note that you can use the GetLogicalXXXRect() commands to obtain the
    // appropriate rect to scale to.
//    MapScreenSizeToDevice();
//    wxRect fitRect = GetLogicalPageRect();

    // Each of the preceding Fit or Map routines positions the origin so that
    // the drawn image is positioned at the top left corner of the reference
    // rectangle. You can easily center or right- or bottom-justify the image as
    // follows.

    // This offsets the image so that it is centered within the reference
    // rectangle defined above.
    wxCoord xoff = (fitRect.width - maxX) / 2;
    wxCoord yoff = (fitRect.height - maxY) / 2;
    OffsetLogicalOrigin(xoff, yoff);

    // This offsets the image so that it is positioned at the bottom right of
    // the reference rectangle defined above.
//    wxCoord xoff = (fitRect.width - maxX);
//    wxCoord yoff = (fitRect.height - maxY);
//    OffsetLogicalOrigin(xoff, yoff);

    frame->Draw(*GetDC());
}

void MyPrintout::DrawPageTwo()
{
    // You might use THIS code to set the printer DC to ROUGHLY reflect
    // the screen text size. This page also draws lines of actual length
    // 5cm on the page.

    // Compare this to DrawPageOne(), which uses the really convenient routines
    // from wxPrintout to fit the screen image onto the printed page. This page
    // illustrates how to do all the scaling calculations yourself, if you're so
    // inclined.

    wxDC *dc = GetDC();

    // Get the logical pixels per inch of screen and printer
    int ppiScreenX, ppiScreenY;
    GetPPIScreen(&ppiScreenX, &ppiScreenY);
    int ppiPrinterX, ppiPrinterY;
    GetPPIPrinter(&ppiPrinterX, &ppiPrinterY);

    // This scales the DC so that the printout roughly represents the the screen
    // scaling. The text point size _should_ be the right size but in fact is
    // too small for some reason. This is a detail that will need to be
    // addressed at some point but can be fudged for the moment.
    float scale = (float)((float)ppiPrinterX/(float)ppiScreenX);

    // Now we have to check in case our real page size is reduced (e.g. because
    // we're drawing to a print preview memory DC)
    int pageWidth, pageHeight;
    int w, h;
    dc->GetSize(&w, &h);
    GetPageSizePixels(&pageWidth, &pageHeight);

    // If printer pageWidth == current DC width, then this doesn't change. But w
    // might be the preview bitmap width, so scale down.
    float overallScale = scale * (float)(w/(float)pageWidth);
    dc->SetUserScale(overallScale, overallScale);

    // Calculate conversion factor for converting millimetres into logical
    // units. There are approx. 25.4 mm to the inch. There are ppi device units
    // to the inch. Therefore 1 mm corresponds to ppi/25.4 device units. We also
    // divide by the screen-to-printer scaling factor, because we need to
    // unscale to pass logical units to DrawLine.

    // Draw 50 mm by 50 mm L shape
    float logUnitsFactor = (float)(ppiPrinterX/(scale*25.4));
    float logUnits = (float)(50*logUnitsFactor);
    dc->SetPen(* wxBLACK_PEN);
    dc->DrawLine(50, 250, (long)(50.0 + logUnits), 250);
    dc->DrawLine(50, 250, 50, (long)(250.0 + logUnits));

    dc->SetBackgroundMode(wxTRANSPARENT);
    dc->SetBrush(*wxTRANSPARENT_BRUSH);

    { // GetTextExtent demo:
        wxString words[7] = {_T("This "), _T("is "), _T("GetTextExtent "), _T("testing "), _T("string. "), _T("Enjoy "), _T("it!")};
        long w, h;
        long x = 200, y= 250;
        wxFont fnt(15, wxSWISS, wxNORMAL, wxNORMAL);

        dc->SetFont(fnt);

        for (int i = 0; i < 7; i++)
        {
            wxString word = words[i];
            word.Remove( word.Len()-1, 1 );
            dc->GetTextExtent(word, &w, &h);
            dc->DrawRectangle(x, y, w, h);
            dc->GetTextExtent(words[i], &w, &h);
            dc->DrawText(words[i], x, y);
            x += w;
        }

    }

    dc->SetFont(wxGetApp().m_testFont);

    dc->DrawText(_T("Some test text"), 200, 300 );

    // TESTING

    int leftMargin = 20;
    int rightMargin = 20;
    int topMargin = 20;
    int bottomMargin = 20;

    int pageWidthMM, pageHeightMM;
    GetPageSizeMM(&pageWidthMM, &pageHeightMM);

    float leftMarginLogical = (float)(logUnitsFactor*leftMargin);
    float topMarginLogical = (float)(logUnitsFactor*topMargin);
    float bottomMarginLogical = (float)(logUnitsFactor*(pageHeightMM - bottomMargin));
    float rightMarginLogical = (float)(logUnitsFactor*(pageWidthMM - rightMargin));

    dc->SetPen(* wxRED_PEN);
    dc->DrawLine( (long)leftMarginLogical, (long)topMarginLogical,
        (long)rightMarginLogical, (long)topMarginLogical);
    dc->DrawLine( (long)leftMarginLogical, (long)bottomMarginLogical,
        (long)rightMarginLogical,  (long)bottomMarginLogical);

    WritePageHeader(this, dc, _T("A header"), logUnitsFactor);
}

// Writes a header on a page. Margin units are in millimetres.
bool WritePageHeader(wxPrintout *printout, wxDC *dc, const wxChar *text, float mmToLogical)
{
/*
static wxFont *headerFont = (wxFont *) NULL;
if (!headerFont)
{
headerFont = wxTheFontList->FindOrCreateFont(16, wxSWISS, wxNORMAL, wxBOLD);
}
dc->SetFont(headerFont);
    */

    int pageWidthMM, pageHeightMM;

    printout->GetPageSizeMM(&pageWidthMM, &pageHeightMM);
    wxUnusedVar(pageHeightMM);

    int leftMargin = 10;
    int topMargin = 10;
    int rightMargin = 10;

    float leftMarginLogical = (float)(mmToLogical*leftMargin);
    float topMarginLogical = (float)(mmToLogical*topMargin);
    float rightMarginLogical = (float)(mmToLogical*(pageWidthMM - rightMargin));

    long xExtent, yExtent;
    dc->GetTextExtent(text, &xExtent, &yExtent);
    float xPos = (float)(((((pageWidthMM - leftMargin - rightMargin)/2.0)+leftMargin)*mmToLogical) - (xExtent/2.0));
    dc->DrawText(text, (long)xPos, (long)topMarginLogical);

    dc->SetPen(* wxBLACK_PEN);
    dc->DrawLine( (long)leftMarginLogical, (long)(topMarginLogical+yExtent),
        (long)rightMarginLogical, (long)topMarginLogical+yExtent );

    return true;
}