From: "Joe C. Hecht" <joehecht@gte.net>
Subject: Re: changing printer orientation [long and technical explanation]
Date: 21 Jan 1999 00:00:00 GMT
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Robert Kennedy wrote:
>
> Using Delphi 3, is there a way to change the orientation of the printer
> from portrait to landscape in mid print job?  I can stop the job,
> reorient, then continue printing in a new job but this is
> unsatisfactory.
>
> Is there a way to do it without producing multiple print jobs?
>
> Using this statement in mid print job causes an error.
> Printer.orientation := poLandscape;
>
> Thanks for any help or suggestions.
>
> Robert Kennedy

Yes, it is perhaps possible to change many of the settings
of between pages a printjob. I thought that I had written
a Ti or FAQ detailing how to do this, but I am unable to
locate it.

Basically, you will need to patch TPrinter to make a callback
to a unit that will sit between you and TPrinter. This is an
interesting workaround. I have been told (by the father of
Delphi himself and other notables) that you cannot make changes
to TPrinters interface without risking breaking other VCL code.
The workaround is rather simple. Create you intermediate unit,
and reference it only from the *implementation* section of
TPrinter.

You want to create a callback to the intermediate unit that
occures *between* every page that is printed. You can assign
a callback in the intermediate unit from your application,
so that your callback function in your application will get
called whenever the callback funcion in the intermediate unit
gets called. From there, you can get access to the printers
DevMode structure and use API functions like ReSetDc()
to attempt to change the printer setup in between pages.

ResetDC() is pretty good about reporting if the printer
supports this escape, and if the call fails (rarely),
your application can seperate the pages into individual
print jobs. Note that most print drivers do support
changing the settings between jobs.

[As a technical side note, the ResetDC() function actually
makes an escape call into 16 bit drivers (IMHO, is not well
documented for 16 bit dirvers). A further note is that non
NT platforms use 16 bit print drivers (although some of them
are actuall marked as 32 bit dlls)].

A well implemenated unit can make it very painless to use
these features without ever touching the interface section
of TPrinter.

Sorry to say, I cannot directly post the code, however
(and here comes the plug), the code is contined in a book
that I took part in authoring called "Delphi 3 Special Edition"
published by Que.

Please note that I have tried to be specific enough in the
general theory for you to implement a suitiable workaround,
and that I recieve no royalties should your decide to purchase
the book. ie: I have no financial interest in selling you anything.

On the other hand, you may find some of the tips and techniques
contained in the book to be a valuable asset, especally if you
are doing graphics, printing, or wirking with the Windows API.

Joe
--
Joe C. Hecht
http://home1.gte.net/joehecht/index.htm