Re: Argh: Why are arrows clipped to the graph?

[Daniel J S. <dan...@ie...>]

Aapo Lankinen wrote:
> On Wed, 2005-11-09 at 16:13 -0800, Ethan Merritt wrote:
> 
>>Well, in this particular case it is caused by the fact that when
>>post.trm expands its drawing limits, it does not change the values
>>of term->xmax and term->ymax.   Therefore if you clip against them,
>>it doesn't work.  So far as I know, other terminal drivers
>>correctly report what their actual limiting coordinates are.
> 
> 
> What is the exact reason that prevents fixing post.trm (and maybe other
> broken terminals) so that it would correctly update term->xmax and
> term->ymax?  I would imagine that it wouldn't be terribly difficult to
> change accordingly the values of these two variables when the postscript
> internal canvas grow.  Is it somehow a problem with backward
> compatibility?

I don't see why things have to be done this way.  Does "canvas" have the same meaning as "view port".  The thing is, in PostScript I don't think one has to worry at all about plotting beyond the "view port".  (Sorry, P.S. terminology isn't fresh in my mind right now.)  It automatically takes care of that, doesn't it?  Why impose some inferior clipping method?

Instead, in the case of P.S., interpret term->xmax and term->ymax as simply boundaries of where the plot is viewed.  Or, if those aren't the appropriate variables, conceptually I hope you understand my point.  Also, write a nicer do_arrow(), as Ethan suggests.  I think I could do it fairly easily, but I simply don't have time now.  It would have to wait until after the holidays.

Now, although that doesn't seem too difficult, there is a similar thing with the new image code.  One starts out writing a generic thing, but I now know--after having looked at PostScript books in the process of working on PostScript images--that eventually improvements can be made for PostScript images plotted at an angle.  Believe it or not, PostScript can have a viewing angle for rectangular images.  I think for now, the generic pixel (parallelogram) by pixel (parallelogram) method will have to do.

[Ethan, I hope that adding a view angle or such to the image terminal routine down the road doesn't cause any problems.  If so, perhaps we should think about that before the next release.]

Dan