src/display.lisp

   1 (in-package :lisp-on-lines)
   2
   3 (defvar *description*)
   4 (defvar *display*)
   5 (defvar *object*)
   6
   7 (deflayer display-layer)
   8
   9 (define-layered-function display-using-description (description display object &rest args)
  10   (:documentation
  11    "Displays OBJECT via description using/in/with/on display"))
  12
  13 (defun display (display object &rest args &key attributes )
  14   (let ((*display-attributes* attributes))
  15     (display-using-description (description-of object) display object args)))
  16
  17 (define-layered-method display-using-description
  18   :around (description display object &rest args)
  19   (declare (ignorable args))
  20   (let ((*description* description)
  21         (*display* display)
  22         (*object*  object))
  23     (call-next-method)))
  24
  25 (defun display/d (&rest args)
  26   (apply #'display-using-description args))
  27
  28
  29
  30 (define-layered-method display-using-description (description display object &rest args)
  31  (error "No DISPLAY-USING-DESCRIPTION methods are specified for: ~%  DESCRIPTION: ~A ~%  DISPLAY: ~A ~%  OBJECT: ~A ~%  ARGS: ~S
  32
  33 OMGWTF! If you didn't do this, it's a bug!" description display object args))
  34
  35
  36
  37 (defmacro define-display (&body body)
  38   (loop with in-descriptionp = (eq (car body) :in-description)
  39         with description = (if in-descriptionp (cadr body) 't)
  40         for tail on (if in-descriptionp (cddr body) body)
  41         until (listp (car tail))
  42         collect (car tail) into qualifiers
  43         finally
  44         (when (member :in-description qualifiers)
  45           (error "Incorrect occurrence of :in-description in defdisplay. Must occur before qualifiers."))
  46         (return
  47           (destructuring-bind (description-spec &optional  (display-spec (gensym)) (object-spec (gensym)))
  48               (car tail)
  49                 `(define-layered-method
  50                   display-using-description
  51                    :in-layer ,(if (eq t description)
  52                                   t
  53                                   (defining-description description))
  54                    ,@qualifiers
  55                    (,(if (listp description-spec)
  56                         (list (first description-spec)
  57                              (if (eq 'description (second description-spec))
  58                                      'description
  59                                      (defining-description (second description-spec)))))
  60                    ,display-spec
  61                    ,object-spec &rest args)
  62                    (declare (ignorable args))
  63                    ,@(cdr tail))))))
  64
  65
  66
  67