Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!tut.cis.ohio-state.edu!bloom-beacon!apple!voder!pyramid!decwrl!shelby!polya!ali
From: ali@polya.Stanford.EDU (Ali T. Ozer)
Newsgroups: comp.sys.next
Subject: Re: App printing problem
Message-ID: <8969@polya.Stanford.EDU>
Date: 5 May 89 14:51:12 GMT
References: <1601@hub.ucsb.edu>
Sender: Ali T. Ozer <ali@polya.Stanford.EDU>
Reply-To: aozer@NeXT.com (Ali Ozer)
Organization: .
Lines: 31

In article <1601@hub.ucsb.edu> trainoff@sbphy.ucsb.edu writes:
>I have just written my first App.  I created a CustomView that
>basically emulates a graphics library ...  The print: method just
>calls [self printPSCode:self] This correctly fires up a print panel
>and spools a file to the printer.  The problem is that it prints two
>blank pages, not what is on the screen.  I traced the problem down to
>the fact that I had implemented a bunch of methods in my View that
>send PS to the current context via pswrap routines or PSxxxx() calls.
>I did not, however, create a drawSelf:: method.  Evidently
>printPSCode: calls display or drawSelf:: to create its page.  

Every view should implement drawSelf::, and drawSelf:: should be able
to recreate whatever is visible in the view at the time it is called.
It's possible to create views that do not have drawSelf:: methods, of
course, but then you run into problems such as the above. 

If you do not create a drawSelf:: method, then you are probably using
some other mechanism to draw in your view. That makes your view highly
unportable; as you noticed, it becomes harder to print, and it will
also be harder to do such things as put your view in an Interface
Builder palette, or cut/copy PostScript from your view into the
pasteboard, to put your view in a ScrollView, and so on. With
drawSelf:: in place, and correctly working, the above tasks reduce to
a few lines (if any) of code.

You might want to create a drawSelf:: method that calls your other drawing
routines in the correct order to recreate what's in the view. Leave
everything else as it is...

Ali Ozer, NeXT Developer Support
aozer@NeXT.com