docs/latex/wx/tprint.tex

   1 \section{Printing overview}\label{printingoverview}
   2
   3 Classes: \helpref{wxPrintout}{wxprintout},
   4 \helpref{wxPrinter}{wxprinter},
   5 \helpref{wxPrintPreview}{wxprintpreview},
   6 \helpref{wxPrinterDC}{wxprinterdc},
   7 \helpref{wxPostScriptDC}{wxpostscriptdc},
   8 \helpref{wxPrintDialog}{wxprintdialog},
   9 \helpref{wxPrintData}{wxprintdata},
  10 \helpref{wxPrintDialogData}{wxprintdialogdata},
  11 \helpref{wxPageSetupDialog}{wxpagesetupdialog},
  12 \helpref{wxPageSetupDialogData}{wxpagesetupdialogdata}
  13
  14 The printing framework relies on the application to provide classes whose member
  15 functions can respond to particular requests, such as `print this page' or `does
  16 this page exist in the document?'. This method allows wxWidgets to take over the
  17 housekeeping duties of turning preview pages, calling the print dialog box,
  18 creating the printer device context, and so on: the application can concentrate
  19 on the rendering of the information onto a device context.
  20
  21 In most cases, the only class you will need to derive from is
  22 \helpref{wxPrintout}{wxprintout}; all others will be used as-is.
  23
  24 A brief description of each class's role and how they work together follows.
  25
  26 \subsection{\helpref{wxPrintout}{wxprintout}}
  27
  28 A document's printing ability is represented in an application by a derived
  29 wxPrintout class. This class prints a page on request, and can be passed to the
  30 Print function of a wxPrinter object to actually print the document, or can be
  31 passed to a wxPrintPreview object to initiate previewing. The following code
  32 (from the printing sample) shows how easy it is to initiate printing, previewing
  33 and the print setup dialog, once the wxPrintout functionality has been defined.
  34 Notice the use of MyPrintout for both printing and previewing. All the preview
  35 user interface functionality is taken care of by wxWidgets. For more details on how
  36 MyPrintout is defined, please look at the printout sample code.
  37
  38 \begin{verbatim}
  39     case WXPRINT_PRINT:
  40     {
  41       wxPrinter printer;
  42       MyPrintout printout("My printout");
  43       printer.Print(this, &printout, true);
  44       break;
  45     }
  46     case WXPRINT_PREVIEW:
  47     {
  48       // Pass two printout objects: for preview, and possible printing.
  49       wxPrintPreview *preview = new wxPrintPreview(new MyPrintout, new MyPrintout);
  50       wxPreviewFrame *frame = new wxPreviewFrame(preview, this, "Demo Print Preview", wxPoint(100, 100), wxSize(600, 650));
  51       frame->Centre(wxBOTH);
  52       frame->Initialize();
  53       frame->Show(true);
  54       break;
  55     }
  56 \end{verbatim}
  57
  58 Class \helpref{wxPrintout}{wxprintout} assembles the printed page and (using
  59 your subclass's overrides) writes requested pages to a \helpref{wxDC}{wxdc} that
  60 is passed to it. This wxDC could be a \helpref{wxMemoryDC}{wxmemorydc} (for
  61 displaying the preview image on-screen), a \helpref{wxPrinterDC}{wxprinterdc}
  62 (for printing under MSW and Mac), or a \helpref{wxPostScriptDC}{wxpostscriptdc}
  63 (for printing under GTK or generating PostScript output).
  64
  65 The \helpref{document/view framework}{docviewoverview} creates a default
  66 wxPrintout object for every view, calling wxView::OnDraw to achieve a
  67 prepackaged print/preview facility.
  68
  69 If your window classes have a Draw(wxDC *dc) routine to do screen rendering,
  70 your wxPrintout subclass will typically call those routines to create portions
  71 of the image on your printout. Your wxPrintout subclass can also make its own
  72 calls to its wxDC to draw headers, footers, page numbers, etc.
  73
  74 The scaling of the drawn image typically differs from the screen to the preview
  75 and printed images. This class provides a set of routines named
  76 FitThisSizeToXXX(), MapScreenSizeToXXX(), and GetLogicalXXXRect, which can be
  77 used to set the user scale and origin of the wxPrintout's DC so that your class
  78 can easily map your image to the printout withough getting into the details of
  79 screen and printer PPI and scaling. See the printing sample for examples of how
  80 these routines are used.
  81
  82 \subsection{\helpref{wxPrinter}{wxprinter}}
  83
  84 Class wxPrinter encapsulates the platform-dependent print function with a common
  85 interface. In most cases, you will not need to derive a class from wxPrinter;
  86 simply create a wxPrinter object in your Print function as in the example above.
  87
  88 \subsection{\helpref{wxPrintPreview}{wxprintpreview}}
  89
  90 Class wxPrintPreview manages the print preview process. Among other things, it
  91 constructs the wxDCs that get passed to your wxPrintout subclass for printing
  92 and manages the display of multiple pages, a zoomable preview image, and so
  93 forth. In most cases you will use this class as-is, but you can create your own
  94 subclass, for example, to change the layout or contents of the preview window.
  95
  96
  97 \subsection{\helpref{wxPrinterDC}{wxprinterdc}}
  98
  99 Class wxPrinterDC is the wxDC that represents the actual printed page under MSW
 100 and Mac. During printing, an object of this class will be passed to your derived
 101 wxPrintout object to draw upon. The size of the wxPrinterDC will depend on the
 102 paper orientation and the resolution of the printer.
 103
 104 There are two important rectangles in printing: the \em{page rectangle} defines
 105 the printable area seen by the application, and under MSW and Mac, it is the
 106 printable area specified by the printer. (For PostScript printing, the page
 107 rectangle is the entire page.) The inherited function
 108 \helpref{wxDC::GetSize}{wxdcgetsize} returns the page size in device pixels. The
 109 point (0,0) on the wxPrinterDC represents the top left corner of the page
 110 rectangle; that is, the page rect is given by wxRect(0, 0, w, h), where (w,h)
 111 are the values returned by GetSize.
 112
 113 The \em{paper rectangle}, on the other hand, represents the entire paper area
 114 including the non-printable border. Thus, the coordinates of the top left corner
 115 of the paper rectangle will have small negative values, while the width and
 116 height will be somewhat larger than that of the page rectangle. The
 117 wxPrinterDC-specific function
 118 \helpref{wxPrinterDC::GetPaperRect}{wxprinterdcgetpaperrect} returns the paper
 119 rectangle of the given wxPrinterDC.
 120
 121 \subsection{\helpref{wxPostScriptDC}{wxpostscriptdc}}
 122
 123 Class wxPostScriptDC is the wxDC that represents the actual printed page under
 124 GTK and other PostScript printing. During printing, an object of this class will
 125 be passed to your derived wxPrintout object to draw upon. The size of the
 126 wxPostScriptDC will depend upon the \helpref{wxPrintData}{wxprintdata} used to
 127 construct it.
 128
 129 Unlike a wxPrinterDC, there is no distinction between the page rectangle and the
 130 paper rectangle in a wxPostScriptDC; both rectangles are taken to represent the
 131 entire sheet of paper.
 132
 133 \subsection{\helpref{wxPrintDialog}{wxprintdialog}}
 134
 135 Class wxPrintDialog puts up the standard print dialog, which allows you to
 136 select the page range for printing (as well as many other print settings, which
 137 may vary from platform to platform). You provide an object of type
 138 \helpref{wxPrintDialogData}{wxprintdialogdata} to the wxPrintDialog at
 139 construction, which is used to populate the dialog.
 140
 141 \subsection{\helpref{wxPrintData}{wxprintdata}}
 142
 143 Class wxPrintData is a subset of wxPrintDialogData that is used (internally) to
 144 initialize a wxPrinterDC or wxPostScriptDC. (In fact, a wxPrintData is a data
 145 member of a wxPrintDialogData and a wxPageSetupDialogData). Essentially,
 146 wxPrintData contains those bits of information from the two dialogs necessary to
 147 configure the wxPrinterDC or wxPostScriptDC (e.g., size, orientation, etc.). You
 148 might wish to create a global instance of this object to provide call-to-call
 149 persistence to your application's print settings.
 150
 151 \subsection{\helpref{wxPrintDialogData}{wxprintdialogdata}}
 152
 153 Class wxPrintDialogData contains the settings entered by the user in the print
 154 dialog. It contains such things as page range, number of copies, and so forth.
 155 In most cases, you won't need to access this information; the framework takes
 156 care of asking your wxPrintout derived object for the pages requested by the
 157 user.
 158
 159 \subsection{\helpref{wxPageSetupDialog}{wxpagesetupdialog}}
 160
 161 Class wxPageSetupDialog puts up the standard page setup dialog, which allows you
 162 to specify the orientation, paper size, and related settings. You provide it
 163 with a wxPageSetupDialogData object at intialization, which is used to populate
 164 the dialog; when the dialog is dismissed, this object contains the settings
 165 chosen by the user, including orientation and/or page margins.
 166
 167 Note that on Macintosh, the native page setup dialog does not contain entries
 168 that allow you to change the page margins. You can use the Mac-specific class
 169 wxMacPageMarginsDialog (which, like wxPageSetupDialog, takes a
 170 wxPageSetupDialogData object in its constructor) to provide this capability; see
 171 the printing sample for an example.
 172
 173 \subsection{\helpref{wxPageSetupDialogData}{wxpagesetupdialogdata}}
 174
 175 Class wxPageSetupDialogData contains settings affecting the page size (paper
 176 size), orientation, margins, and so forth. Note that not all platforms populate
 177 all fields; for example, the MSW page setup dialog lets you set the page margins
 178 while the Mac setup dialog does not.
 179
 180 You will typically create a global instance of each of a wxPrintData and
 181 wxPageSetupDialogData at program initiation, which will contain the default
 182 settings provided by the system. Each time the user calls up either the
 183 wxPrintDialog or the wxPageSetupDialog, you pass these data structures to
 184 initialize the dialog values and to be updated by the dialog. The framework then
 185 queries these data structures to get information like the printed page range
 186 (from the wxPrintDialogData) or the paper size and/or page orientation (from the
 187 wxPageSetupDialogData).
 188
 189
 190
 191 \section{Printing under Unix (GTK+)}\label{unixprinting}
 192
 193 Printing under Unix has always been a cause of problems as Unix
 194 does not provide a standard way to display text and graphics
 195 on screen and print it to a printer using the same application
 196 programming interface - instead, displaying on screen is done
 197 via the X11 library while printing has to be done with using
 198 PostScript commands. This was particularly difficult to handle
 199 for the case of fonts with the result that only a selected
 200 number of application could offer WYSIWYG under Unix. Equally,
 201 wxWidgets offered its own printing implementation using PostScript
 202 which never really matched the screen display.
 203
 204 Starting with version 2.8.X, the GNOME project provides printing
 205 support through the libgnomeprint and libgnomeprintui libraries
 206 by which especially the font problem is mostly solved. Beginning
 207 with version 2.5.4, the GTK+ port of wxWidgets can make use of
 208 these libraries if wxWidgets is configured accordingly and if the
 209 libraries are present. You need to configure wxWidgets with the
 210 {\it configure --with-gnomeprint} switch and you application will
 211 then search for the GNOME print libraries at runtime. If they
 212 are found, printing will be done through these, otherwise the
 213 application will fall back to the old PostScript printing code.
 214 Note that the application will not require the GNOME print libraries
 215 to be installed in order to run (there will be no dependency on
 216 these libraries).
 217
 218 It is expected that the printing code that is currently implemented
 219 in the GNOME print libraries will be moved into GTK+ later.
 220