Editing GNU TeXmacs (section)

==== Graphics ====
Graphics objects are also part of the TeXmacs format and can be manipulated programmatically from Scheme. An example of TeXmacs graphics generated in a TeXmacs Scheme session is shown below together with the session which generated the image. Images generated programmatically in a Scheme session can also be edited using the internal drawing editor, as they are inserted in the document as a tree; Scheme scripts can also be executed through the <code>extern</code> TeXmacs macro—in this case only the typeset material is available in the document and no direct editing is possible (the modifications must be made within the Scheme code).<syntaxhighlight lang="scheme">
Scheme]  (define pi (acos -1))
;; A function to define a point in the TeXmacs graphics format using two coordinates
Scheme]  (define (pt x y)
  ‘(point ,(number->string x) ,(number->string y)))
;; Set points
Scheme]  (define xC (- (* 2 (cos (/ pi 3)))))
Scheme]  (define yC (* 2 (sin (/ pi 3))))
Scheme]  (define pA (pt -2 0))
Scheme]  (define pB (pt 2 0))
Scheme]  (define pC (pt xC yC))
Scheme]  (define tA (pt -2.3 -0.5))
Scheme]  (define tB (pt 2.1 -0.5))
Scheme]  (define tC (pt (- xC 0.2) (+ yC 0.2)))
;; Generate graphics
Scheme]  (stree->tree
 ‘(with "gr-geometry" (tuple "geometry" "400px" "300px" "center")
    (graphics
      (with "color" "blue"  (text-at (TeXmacs) ,(pt -0.55 -0.75)))
      (with "color" "black" (arc ,pA ,pC ,pB))
      (with "color" "black" (line ,pA ,pB))
      (with "color" "red"   (cline ,pA ,pB ,pC))
      (with "color" "black" (text-at "A" ,tA))
      (with "color" "black" (text-at "B" ,tB))
      (with "color" "black" (text-at "C" ,tC)))))

</syntaxhighlight>[[File:TeXmacs graphics sample - triangle in a half-circle.png|alt=|frameless|360x360px]]