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

[Dmitriy Ivanov]

Hello Marc,

| Hi Dmitriy,
|
| If you set *use-exact-char-boxes* to t then the characters on a line
| will use their real bounding box like it is defined in the char
| metrics. If it is set to t then the height of the bounding box will be
| replaced by the value of *leading* to ensure that the lines have all
| the same leading.

Not sure. According to make-char-box, if *use-exact-char-boxes* is set to
nil, the height is replaced by *leading*. On the contrary, when it is t, the
height is determined by ascender and descender. The same should be done for
make-white-char-box, see my version below. With this approach the *leading*
is really gone so I have to the following hack to fit-lines:

(defmethod fit-lines ((content text-content) dx dy &optional (v-align
:top)(advance t))
   ... ;snip
   (setf (boxes text-line)(nreverse line-boxes))
   ;; ugly hack: somehow catch and respect current *leading*
   (when *use-exact-char-boxes*
      (let ((delta-size (- *leading* (dy text-line))))
         (when (plusp delta-size)
            (incf (dy text-line) delta-size)
            (incf (internal-baseline text-line) delta-size))))
 ...)

(defun make-white-char-box (char &optional (trimmable-p t))
  ;; DI: In exact mode, we must also use ascender for not making baseline
too large.
  (if *use-exact-char-boxes*
      (multiple-value-bind (width ascender descender)
          (pdf:get-char-size char *font* *font-size*)
        (setq width (* width *text-x-scale*))
        (make-instance 'white-char-box :trimmable-p trimmable-p
                       :dx width
                       :dy (- ascender descender)  :baseline ascender
                       :max-expansion (* width 10) :max-compression (* width
0.7)
                       :expansibility (* width 2.0) :compressibility width))
      (let ((width (* (pdf:get-char-width char *font* *font-size*)
*text-x-scale*)))
        (make-instance 'white-char-box :trimmable-p trimmable-p
                       :dx width
                       :dy *leading*  :baseline *font-size*
                       :max-expansion (* width 10) :max-compression (* width
0.7)
                       :expansibility (* width 2.0) :compressibility
width))))

| In fact generally you want to have the same leading for all the lines.
| I added *use-exact-char-boxes* for the math mode to deal with the
| special math characters.

It would be better to have both *use-exact-char-boxes* and *leading* working
together :-)

| BTW it was nice to meet you at the ECLM. I hope you have recovered your
| voice... ;-)

It is fine now, thanks :-)
--
Sincerely,
Dmitriy Ivanov
lisp.ystok.ru