[cl-typesetting-devel] *use-exact-char-boxes*

[Dmitriy Ivanov]

Marc Battyani wrote on Mon, 15 May 2006 17:07:42 +0200 18:07:

| In fact, the only bug is the character descent missing in the first
| table.
| 
| In make-char-box:
| :dy *leading* :baseline *font-size*
| should be replaced by something like:
| :dy *leading* :baseline (- *font-size* *descender*)
| With *descender* being the maximum descender for the font.
| Or better by adddding *base-line*:
| :dy *leading* :baseline *base-line*

I have found quite a simple solution working when
*use-exact-char-boxes* is nil.

The descender slot is already present in every pdf::font-metrics instance.
It
holds a minumum descender (as descenders are non-positive norlmally) among
the characters of the font. So we can add the same slot to the font class
definition (see cl-pdf/font.lisp):

(defclass font ()
((name :accessor name :initform "helvetica" :initarg :name)
  ...
  ;; minimum descender among chars
  (descender :accessor descender :initform 0)))

are simply copy it on initializing:

(defmethod initialize-instance :after ((font font) &key encoding
                                                &allow-other-keys)
  (let ((font-metrics (gethash (name font) *font-metrics*)))
    ...
    (setf (font-metrics font) font-metrics
          (descender font) (descender font-metrics))
  ...)))

In cl-typesetting, we are using the value of the font descender in
make-char-box and make-white-char-box.

My gut feeling is that the font ascender should be used similarly somewhere
but I cannot figure out where.

I will provide a patch as soon as I resolve troubles with
updating/committing from/to the repository.
--
Sincerely,
Dmitriy Ivanov
lisp.ystok.ru