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Printing Notes
This is a collection of notes from a discussion of an attempt at design of a common printing system for Rebol3.
For Rebol2, there are scattered attempts at some form of simple printing system. Such examples are John Niclasen's postscript.r dialect, which allows direct printing to a few postscript printers.
However, it does not take any advantage of the OS that Rebol2 resides on for printing, which means no access do official OS print dialogs and worse, no access to the printer driver.
It is therefore, sadly, a process that requires great effort to print simple things in Rebol2.
This must change for Rebol3 in an effort to bring true, easy printing to Rebol3.
- Printing should work natively on Windows, Linux and MacOSX. This means accessing OS printer drivers and use the native printer dialog in the same way as Rebol is capable of using the native file requester.
- A finished Rebol3 should be able to access the printer system for its respective platform out of the box.
- If the printing system for a specific platform is not available, Rebol3 should still be able to function without it.
- What we can draw should be printable.
Having WYSIWYG for DRAW would be a great asset, not only for simple desktop publishing, but for any kind of printing that requires just a bit more than text, such as straight lines. Since most drawing operations are done with DRAW (some are limited effects constructed with GOBs), it makes sense to start with DRAW and work from there.
DRAW is optimized for the screen, and in order to print, the same dialect should be used for a printable output. This is considered the easiest way to print what we can see on screen. A print dialect would also have additional features for printer friendly output, such as setting margins and paper sizes in a friendly and recognizable way.
It should be possible to take a DRAW block and feed it to the printer dialect without problems.
The Print Dialect is output specific. On Windows it would output one dataset, suitable for Windows printer driver systems. On MacOSX, it would use a different set. Generic printing systems like Postscript and PCL should be supported as well. These are necessary in cases where you may want to access the printer directly or that the OS does not have printer support.
That printing is a platform specific task is unavoidable, but we can do some things to reduce the dependability, by using common code right out to the printer driver. From the OS, platform specific code is necessary to take care of this task. It is expected that all code that is needed, will be possible to make in the open part of Rebol3, so the whole printing system is open source.
There are many types of printing systems available for Windows. It's worth considering which ones are useful (i.e. most compatible) and which ones are not.
- GDI : This is the most common form of printing in Windows for legacy applications. It's a C compatible API that goes back to 16-bit Windows. C++ is not required.
- GDI+ : This system was introduced in Windows XP and 2003, with runtimes available for Windows NT 4.0 SP6, 98, 98SE, Me and 2000. This provides some more capabilities and a simpler, C++ API. Windows 95, and Windows NT prior to 4.0 SP6 are not supported. This is probably our best bet for native printing on Windows, though extensive wrapping will likely be required.
- XPS : This system is new for Windows Vista. It uses .NET 3.0 and is not fully supported on platforms older than Vista. On Windows XP or 2003 with .NET 3.0 installed, XPS is supported through a print-to-file driver. Windows 2000 or earlier is not supported. It is not recommended that Rebol use this system at this time.
Write something about using NSView.
NSView is used for both printing and showing the native printer dialog. For MacOSX, it's usually encouraged to make the printer dialog as a sheet attached to the current window, rather than a dialog. This depends on how Rebol3 will be implemented for MacOSX. We're not that far yet.
Read more about the printing system here: http://developer.apple.com/documentation/Printing/Conceptual/About_MacOSX_Printing/index.html#//apple_ref/doc/uid/20001017.
Write something about postscript.
Since Linux doesn't itself have a native printing requester, one must access either the one for a specific desktop, if there is one .
For Rebol2, file dialogs currently use the built-in file requester, instead of attempting to use a native one. This may be necessary here as well.