[texhax] A question about stretchability and shrinkability

[Pierre MacKay]

Rodolfo Medina wrote:

>Hi all.
>
>Suppose that in a certain place of my text I say something like, e.g.:
>
> \vskip 25 pt
>
>and that I mean exactly 25 pt with no stretchability neither shrinkability.
>Will it be enough to say:
>
> \vskip 25 pt plus 0 pt minus 0 pt
>  
>
It will be too much.  \vskip will not insert stretchable glue unless you 
tell it to. 

But you can get some surprises if you do not take account of interline 
glue values.  If you want a strict baseline to baseline 25 points, you 
also have to make sure that there is no descender depth counted before 
the transition from hmode into vmode.  My own crude but effective way of 
handling this is to insert a vrule of specific depth greater than any 
glyph depth possible, and then either cancel it or  subtract that amount 
from the following \vskip.  Inelegant, perhaps, but it has saved a lot 
of trouble for the past ten years.  It is one way to get \vadjust 
material on the same baseline as the preceding hmode text.  

You can usually check out the accuracy of the \vskip by turning on 
\tracingpages and looking at the log file, although the log sometimes 
unaccountably skips reporting on one or more lines. 

Pierre MacKay