Re: @Diag question

[j . van den hoff]

Jeff Kingston <jeff <at> it.usyd.edu.au> writes:

> 
> > I was not able to find out how to freely position start and
> > end point of links on the object boundary in @Diag.
> 
> Sounds like you need a bit of algebra, as in Section 9.11 of
> the User's Guide.
> 
> > I tried verbatim the example on page 209 of the manual, ...
> > this does _not_ produce the diagram as in the manual.
> 
> It's all a question of how much space is made available to
> the diagram by its context.  If you had used @CD @Diag ...
> instead of @Diag ... for example, you would have got what
> you see in the manual, because only the minimum amount of
> horizontal space is made available to a centred display.
> Lout is basically keen to give as much space as possible
> to everything, on the principle that it is easy to elec
> not to use it if you don't want it.
> 
> Jeff
> 
> 

thanks for this explanation. this (the necessity for @CD) was not obvious to a 
beginner (me, anyway)
from the context of the example. maybe a remark could be added to the manual 
(which is overall very good, by the way!)? --

concerning my initial aim of drawing two (three, four, ...) boxes aligned on a 
"grid" and connected by 'off-center' arrows like this:

     ______   k1 ______
     |    | ---->|    |
     | c1 |      | c2 |   ,
     |    | <----|    |
     ------   k2 ------

I'm still not happy. using low level alignment with white space like this:

@CD
@Diag vsize {5f} hsize {5f} arrowwidth {.5f}
margin {0f}
{
A::@Box 
address@hidden {c sub 1}}
&5f
B::@Box address@hidden {c sub 2}}

C::@Box address@hidden {c sub 3 = k sub 3 cdot int from 0 to t c sub 2 }}

@Line from address@hidden 1.25f}} to address@hidden 1.25f}}
   ylabel address@hidden  {K sub 1}}
@Arrow from address@hidden 1.25f}} to address@hidden 1.25f}}

@Line from address@hidden 1.25f}} to address@hidden 1.25f}}
   ylabelprox {below}
   ylabel address@hidden  {k sub 2}}
@Arrow from address@hidden 1.25f}} to address@hidden 1.25f}}

}

worked OK. I only noted that th `ylabel' on an arrow is not centered on the 
arrow as a whole but rather on the line excluding the arrowhead. this 
necessitates the awkward double drawing of lines (with labels) and arrows to 
get the vertical alignment of k1 and k2 right. question: is this as it should 
be or am I missing something?

but trying to actually use the positioning scheme proposed in the manual I 
ended up with (positions of arrows are not the same as above intentionally):

@CD @Diag 
margin {0c} arrowwidth {.5f}

{ 

6c @Wide 2c @High 
// 
A:: @Box 
   translate { W to 0, 0.5 } 
   2c @Wide 2c @High
   { @CD @Eq { c sub 1 } }

B:: @Box
   translate { E to 1, 0.5 } 
   2c @Wide 2c @High
   { @CD @Eq { c sub 2 } }

@Arrow from address@hidden 0.333c}} to address@hidden 0.333c}}
ylabel address@hidden  {K sub 1}}
@Arrow from address@hidden 0.333c}} to address@hidden 0.333c}} 
ylabel address@hidden  {k sub 2}}

(note that here the arrow labels are actually not aligned as already noted 
above). what's more of a problem to me is that now the boxed text is no longer
centered in the boxes. question: how do I do this right?

joerg
}