drawing lines (new markups with parameters)

[Germain G. Ivanoff-Trinadtzaty]

Dear all,
please help me with these markups.
Thanks,
Germain

\version 2.12.3
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1) Creating a new markup with two (number-pair?) parameters.

- calling :
{ a4-\myline #'(x . y) #'(dx . dy) }

- should produce the same result as :
{ a4-\markup {\postscript #"[0.2 0.4] 0 setdash x y moveto dx dy rline 
stroke"} }

where x, y, dx and dy are numbers.

Tip : reading the file "output-ps.scm" could be of interest (I'm not sure).
Here I have another question : what is the starting point ? (ie, from where 
do we "moveto" (x y) ?
That starting point seems not to change with respect to :
\override TextScript #'self-alignment-X = #CENTER %or #RIGHT or #LEFT
while {a4-"azerty"} does.

----------------
2) Creating another new markup with two (number-pair?) parameters.

- calling :
{a4-\mydraw-line #'(x . y) #'(dx . dy) }    % maybe the name cannot contain 
a "-"

- should produce the same result as :
{ a4-\draw-line #'(dx . dy) } but starting from #'(x . y) instead of #'(0 . 
0)

dx and dy should be offsets from x and y.

For this second function, there is a (inconvenient) work-around :
{
\override  TextScript #'extra-offset = #'(x . y)
a4-\markup \with-dimensions #'(0 . 0) #'(0 . 0) {
 %\override #'(style . dashed-line)    % doesn't work
 %\override #'(thickness . 2)    % ok
 %\override #'(X-offset . 2)        % doesn't work
 \draw-line #'(dx . dy) }
}

Tip :  this is the definition of built-in "draw-line", from 
"define-markup-commands.scm" :

(define-builtin-markup-command (draw-line layout props dest)
 (number-pair?)
 graphic
 ((thickness 1))
 "drawing lines within text /.../"
 (let ((th (* (ly:output-def-lookup layout 'line-thickness)
              thickness))
       (x (car dest))
       (y (cdr dest)))
   (make-line-stencil th 0 0 x y)))

So I wrote this in my .ly file :

#(define-markup-command (zdraw layout props from dest)
 (number-pair? number-pair?)
 graphic
 ;((thickness 1))    ;; because Lilypond complains about "unbounded 
variable thickness"
 "drawing lines within text /.../"
 (let ((th (* (ly:output-def-lookup layout 'line-thickness)
              1))    ;; was "thickness"
       (x (car from))
       (y (cdr from))
       (dx (car dest))
       (dy (cdr dest)))
   (make-line-stencil th x y (+ x dx) (+ y dy))))

But it works as expected only with this calling :
{a4-\markup \with-dimensions #'(0 . 0) #'(0 . 0) { \zdraw #'(5 . 0) #'(10 . 
5) }

How to get rid of this "with-dimensions" ?
Is there a way to specify that the line should be dashed ?

Besides this, typing :
{a4-\markup \with-dimensions #'(0 . 0) #'(0 . 0) { \override #'(thickness . 
3) \zdraw #'(5 . 0) #'(10 . 5) }
has no effect on the thickness of the line.