/////////////////////////////////////////////////////////////////////////////
// Name:        printing
// Purpose:     topic overview
// Author:      wxWidgets team
// RCS-ID:      $Id$
// Licence:     wxWindows license
/////////////////////////////////////////////////////////////////////////////

/*!

 @page printing_overview Printing overview

 Classes: #wxPrintout,
 #wxPrinter,
 #wxPrintPreview,
 #wxPrinterDC,
 #wxPostScriptDC,
 #wxPrintDialog,
 #wxPrintData,
 #wxPrintDialogData,
 #wxPageSetupDialog,
 #wxPageSetupDialogData
 The printing framework relies on the application to provide classes whose member
 functions can respond to particular requests, such as 'print this page' or 'does
 this page exist in the document?'. This method allows wxWidgets to take over the
 housekeeping duties of turning preview pages, calling the print dialog box,
 creating the printer device context, and so on: the application can concentrate
 on the rendering of the information onto a device context.
 In most cases, the only class you will need to derive from is
 #wxPrintout; all others will be used as-is.
 A brief description of each class's role and how they work together follows.
 For the special case of printing under Unix, where various different
 printing backends have to be offered, please have a look at the
 @ref unixprinting_overview.
 @ref topic9_overview
 @ref topic10_overview
 @ref topic11_overview
 @ref topic12_overview
 @ref topic13_overview
 @ref topic14_overview
 @ref topic15_overview
 @ref topic16_overview
 @ref topic17_overview
 @ref topic18_overview


 @section topic9 #wxPrintout

 A document's printing ability is represented in an application by a derived
 wxPrintout class. This class prints a page on request, and can be passed to the
 Print function of a wxPrinter object to actually print the document, or can be
 passed to a wxPrintPreview object to initiate previewing. The following code
 (from the printing sample) shows how easy it is to initiate printing, previewing
 and the print setup dialog, once the wxPrintout functionality has been defined.
 Notice the use of MyPrintout for both printing and previewing. All the preview
 user interface functionality is taken care of by wxWidgets. For more details on how
 MyPrintout is defined, please look at the printout sample code.

 @code
 case WXPRINT_PRINT:
     {
       wxPrinter printer;
       MyPrintout printout("My printout");
       printer.Print(this, , @true);
       break;
     }
     case WXPRINT_PREVIEW:
     {
       // Pass two printout objects: for preview, and possible printing.
       wxPrintPreview *preview = new wxPrintPreview(new MyPrintout, new MyPrintout);
       wxPreviewFrame *frame = new wxPreviewFrame(preview, this, "Demo Print Preview", wxPoint(100, 100), wxSize(600, 650));
       frame-Centre(wxBOTH);
       frame-Initialize();
       frame-Show(@true);
       break;
     }
 @endcode

 Class #wxPrintout assembles the printed page and (using
 your subclass's overrides) writes requested pages to a #wxDC that
 is passed to it. This wxDC could be a #wxMemoryDC (for
 displaying the preview image on-screen), a #wxPrinterDC
 (for printing under MSW and Mac), or a #wxPostScriptDC
 (for printing under GTK or generating PostScript output).
 The @ref docview_overview creates a default
 wxPrintout object for every view, calling wxView::OnDraw to achieve a
 prepackaged print/preview facility.
 If your window classes have a Draw(wxDC *dc) routine to do screen rendering,
 your wxPrintout subclass will typically call those routines to create portions
 of the image on your printout. Your wxPrintout subclass can also make its own
 calls to its wxDC to draw headers, footers, page numbers, etc.
 The scaling of the drawn image typically differs from the screen to the preview
 and printed images. This class provides a set of routines named
 FitThisSizeToXXX(), MapScreenSizeToXXX(), and GetLogicalXXXRect, which can be
 used to set the user scale and origin of the wxPrintout's DC so that your class
 can easily map your image to the printout withough getting into the details of
 screen and printer PPI and scaling. See the printing sample for examples of how
 these routines are used.

 @section topic10 #wxPrinter

 Class wxPrinter encapsulates the platform-dependent print function with a common
 interface. In most cases, you will not need to derive a class from wxPrinter;
 simply create a wxPrinter object in your Print function as in the example above.

 @section topic11 #wxPrintPreview

 Class wxPrintPreview manages the print preview process. Among other things, it
 constructs the wxDCs that get passed to your wxPrintout subclass for printing
 and manages the display of multiple pages, a zoomable preview image, and so
 forth. In most cases you will use this class as-is, but you can create your own
 subclass, for example, to change the layout or contents of the preview window.


 @section topic12 #wxPrinterDC

 Class wxPrinterDC is the wxDC that represents the actual printed page under MSW
 and Mac. During printing, an object of this class will be passed to your derived
 wxPrintout object to draw upon. The size of the wxPrinterDC will depend on the
 paper orientation and the resolution of the printer.
 There are two important rectangles in printing: the page rectangle defines
 the printable area seen by the application, and under MSW and Mac, it is the
 printable area specified by the printer. (For PostScript printing, the page
 rectangle is the entire page.) The inherited function
 wxDC::GetSize returns the page size in device pixels. The
 point (0,0) on the wxPrinterDC represents the top left corner of the page
 rectangle; that is, the page rect is given by wxRect(0, 0, w, h), where (w,h)
 are the values returned by GetSize.
 The paper rectangle, on the other hand, represents the entire paper area
 including the non-printable border. Thus, the coordinates of the top left corner
 of the paper rectangle will have small negative values, while the width and
 height will be somewhat larger than that of the page rectangle. The
 wxPrinterDC-specific function
 wxPrinterDC::GetPaperRect returns the paper
 rectangle of the given wxPrinterDC.

 @section topic13 #wxPostScriptDC

 Class wxPostScriptDC is the wxDC that represents the actual printed page under
 GTK and other PostScript printing. During printing, an object of this class will
 be passed to your derived wxPrintout object to draw upon. The size of the
 wxPostScriptDC will depend upon the #wxPrintData used to
 construct it.
 Unlike a wxPrinterDC, there is no distinction between the page rectangle and the
 paper rectangle in a wxPostScriptDC; both rectangles are taken to represent the
 entire sheet of paper.

 @section topic14 #wxPrintDialog

 Class wxPrintDialog puts up the standard print dialog, which allows you to
 select the page range for printing (as well as many other print settings, which
 may vary from platform to platform). You provide an object of type
 #wxPrintDialogData to the wxPrintDialog at
 construction, which is used to populate the dialog.

 @section topic15 #wxPrintData

 Class wxPrintData is a subset of wxPrintDialogData that is used (internally) to
 initialize a wxPrinterDC or wxPostScriptDC. (In fact, a wxPrintData is a data
 member of a wxPrintDialogData and a wxPageSetupDialogData). Essentially,
 wxPrintData contains those bits of information from the two dialogs necessary to
 configure the wxPrinterDC or wxPostScriptDC (e.g., size, orientation, etc.). You
 might wish to create a global instance of this object to provide call-to-call
 persistence to your application's print settings.

 @section topic16 #wxPrintDialogData

 Class wxPrintDialogData contains the settings entered by the user in the print
 dialog. It contains such things as page range, number of copies, and so forth.
 In most cases, you won't need to access this information; the framework takes
 care of asking your wxPrintout derived object for the pages requested by the
 user.

 @section topic17 #wxPageSetupDialog

 Class wxPageSetupDialog puts up the standard page setup dialog, which allows you
 to specify the orientation, paper size, and related settings. You provide it
 with a wxPageSetupDialogData object at intialization, which is used to populate
 the dialog; when the dialog is dismissed, this object contains the settings
 chosen by the user, including orientation and/or page margins.
 Note that on Macintosh, the native page setup dialog does not contain entries
 that allow you to change the page margins. You can use the Mac-specific class
 wxMacPageMarginsDialog (which, like wxPageSetupDialog, takes a
 wxPageSetupDialogData object in its constructor) to provide this capability; see
 the printing sample for an example.

 @section topic18 #wxPageSetupDialogData

 Class wxPageSetupDialogData contains settings affecting the page size (paper
 size), orientation, margins, and so forth. Note that not all platforms populate
 all fields; for example, the MSW page setup dialog lets you set the page margins
 while the Mac setup dialog does not.
 You will typically create a global instance of each of a wxPrintData and
 wxPageSetupDialogData at program initiation, which will contain the default
 settings provided by the system. Each time the user calls up either the
 wxPrintDialog or the wxPageSetupDialog, you pass these data structures to
 initialize the dialog values and to be updated by the dialog. The framework then
 queries these data structures to get information like the printed page range
 (from the wxPrintDialogData) or the paper size and/or page orientation (from the
 wxPageSetupDialogData).

 */