need help with beginpage and array

[Wolfie7873]

Another newbie question . . . although I think i'm picking up fairly quickly...

From reading the PLRM, I understand there's a way to define a beginpage procedure that will execute when a new page is begun. Can this be used to display a "header" or banner or some other such thing? How do you define such a procedure? The PLRM is a little lacking in concrete examples.

Also, I think I get how to define an array (a useful thing for defining coordinate pairs in user space), but I don't understand the limitations, etc. For example if I say something like:

/inch 72 def
/width 8.5 inch mul def
/height 11 inch mul def
/size 2 array [width height] def
<</PageSize size>>setpagedevice

why doesn't it work? My understanding of the argument needed for PageSize is a 2x1 array and that's what size is, so why doesn't it work?

Eddie

 

[tgreer]

First for the array; you've simply defined it incorrectly.

There are two ways to create an array. One way is to use the array operator to create an emtpy array, and then later fill it:

2 array dup 0 width put 1 height put

That will leave a two element array on the stack, but doesn't associate it in userdict with a key.

The other way is to simply put a mark on the stack: &quot;[&quot;, then your array elements, and then the &quot;]&quot; operator.

Note the terminology: &quot;[&quot; is just a mark. &quot;]&quot; is a special operator that creates an array.

So for your purposes, rewrite your code as follows:

/inch 72 def
/width 8.5 inch mul def
/height 11 inch mul def
/size [width height] def
<</PageSize size>>setpagedevice

Ok, for BeginPage, yes, you can use it for headers, footers, watermarks, pagination, etc.

It works in conjunction with setpagedevice. Here's an example:

<<
   /BeginPage
   { gsave
      /Helvetica 144 selectfont
      45 rotate
      .5 setgray
      288 72  moveto (DRAFT) show
     grestore
   } bind

>> setpagedevice

Whenever you use &quot;showpage&quot;, this procedure will be called &quot;automatically&quot;.


Thomas D. Greer

http://www.tgreer.com

Providing PostScript & PDF
Training, Development & Consulting

 

[Wolfie7873]

OK! I get that - and the fun continues. . . .

if stringwidth returns two values, how do I use them? Is the information stored in an array or is it just two numbers pushed on the stack?

Eddie

 

[tgreer]

Two numbers on the stack. They don't really represent &quot;stringwidth&quot;, that's a misnomer. They represent offsets, in points, that showing the string would create to the currentpoint.

Does that make sense? Stringwidth pushes two numbers on the stack, first the distance that &quot;x&quot; would move, then the distance &quot;y&quot; would move. Unless you're dealing with kanjii fonts, &quot;y&quot; doesn't move. So stringwidth is almost invariably followed by &quot;pop&quot; to discard the useless y value, and preceded by &quot;dup&quot; since stringwidth consumes the string.

&quot;dup stringwidth pop&quot; leaves your original string plus it's &quot;width&quot; on the stack.

You can just it for example to right-justify a string.
If your right margin is say at 512, you could use this code snippet, assuming that &quot;y&quot; is previously defined:

(Right-justify this string) dup stringwidth pop
512 exch sub y moveto show

I noticed the forum removed my square brackets in the previous post, strange, but I think you got the point.

May I ask why you're embarking on PostScript? Just curious.



Thomas D. Greer

http://www.tgreer.com

Providing PostScript & PDF
Training, Development & Consulting

 

[Wolfie7873]

Mr. Greer,
Thank you for your continued help, I think I've almost got it. I'm trying to learn (self-teach, really) PostScript to supplement a utility I'm developing. Suffice it to say that the program I'm writing needs a device-independent printing procedure, and it seems that PostScript is the way to go. I'm writing my utility using C++ and the programmatic approach to device-independent printing appeals to me. I want my end-user to have the option of .txt .ps and .html (eventually, I want to do .pdf, too, but from glancing at that manual, it looks pretty tough). I also want seamless printing from the program. There won't be any paragraphs, just lines of text in certain spots; once i know the basic manipulations, I should be set.

Thanks again
Eddie

 

[Wolfie7873]

One other thing,
I've noticed that drawing the stack makes life a lot easier in terms of understanding PostScript's &quot;backwards&quot; notation.