Re: Move arbitrary text by an offset

[Hans-Bernhard B. <br...@ph...>]

On Sat, 3 Jul 2004, Harald Harders wrote:

> There is one problem with logarithmic axes: It is difficult to handle
> offsets given in plot coordinates (`first', `second') with log axes.
> Hans-Bernhard has suggested to use the coordinates as factors then.
> `offset first 2,2' could mean to put the text to the position with double
> value of the default position. This sounds good to me.

While at it, let's also note that vaguely similar problems exist with
relative positions on time/date axes.  It's surprisingly hard to 
predict what 'set xtics' & friends will do if you specify the tic step 
size explicitly.

There's another precedent to be kept in mind: the 'rto' way of specifying
arrow endpoints relative to their starts instead of absolutely.  All such
usages of relative positions and offsets had better have a consistent user
interface.  E.g. 'rto' could be renamed to 'to offset'.

> - Which kind of interface do you think is best, 

I like the idea you've presented.  'offset' tells the reader of the
command exactly what it does, and it should be easy to memorize.

> and shall all kinds of text output have the `offset' functionality?

Definitely.

> - How shall this new function be implemented? Which function and which
>   struct are to be extended?

Wrap both term->put_text() and write_multiline() into new functions,
term_offset_text() and write_multiline_offset that call the basic 
functions with the appropriate changes to the position.

Which reminds me of another project that feels overdue: splitting term.c
into (at least) 3 parts: routines called by *.trm functions (e.g.  
do_point(), do_arrow()); wrappers around term->foo() functions serving as
a buffer layer between them and the main core of gnuplot, and a .c file
whose sole job it is to #include "term.h".  Effectively, we may end up
renaming term.h to a .c file...

The new "output text with positional offset" functions would go into
the second of those parts.

-- 
Hans-Bernhard Broeker (br...@ph...)
Even if all the snow were burnt, ashes would remain.