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

[Marc Battyani]

Dmitriy Ivanov wrote:

> | 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*.

Yes, it's a typo in my reply, the second t should be nil instead. ;-)

> 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:

OK but why? I mean the *use-exact-char-boxes* is only used for the math mode 
it is not supposed to be used in normal mode.

> (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 :-)

OK but again why? Using *use-exact-char-boxes* when not in math mode will 
give non homogeneous leading for lines.
For instance a line with "man" will have a much smaller leading than one 
with "Man p".

Marc