Re: Where does paper-height come from?

[Alexander Kobel]

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