Re: Where does paper-height come from?

[b1]

Thanks Alexander,

This does indeed look suspiciously close to the truth. 
But which part of the code might do this conversion?  I looked at the 
level of raw module-define! and ly_module_lookup(), I do not see how 
these can contain any conversion code?


Quoting Alexander Kobel <address@hidden>:
> address@hidden wrote:
> > Hi all,
> >
> > I am playing with the vertical spacing algorithms, and am very
> > surprised by the behavior of "page-height". 
> >
> > Let's say for example that I set my paper to A6.  This, by ISO216, is
> > 148mm high. 
> > when calc-printable-height applies (ly:output-def-lookup layout
> > 'paper-height), it ends up in Output_def::lookup_variable() and
> > ultimately in ly_module_lookup().  This does not return 148, but
> > 84.22!!! [...]
>
> Hi. 
>
> Are you aware of the units?  I'm not at all, and neither did have a look
> in the code, but 84.22 is suspiciously near to 148 / (7/4), where the
> parenthesized term is 7 mm per 4 staff units, which is (not considering
> rounding errors) the default global staff size. 
> More accurate: I think LilyPond uses a pt size of 1/72.27 in, so a staff
> (with four staff units) has height 20*25.4/72.27 mm = 7.0292 mm, and 148
> / (7.0292 / 4) = 84.22 to a precision of three digits. 
>
> So I'm quite sure that the output of output-def-lookup is in global
> staff size units, not in mm, and a conversion happening somewhere hidden
> in the code, and not specifically for page-height. 
>
>
> HTH,
> Alexander