Re: Slur with left and/or right arrow head

[Aaron Hill]

On 2019-04-19 3:29 am, Thomas Morley wrote:
> Am Mi., 17. Apr. 2019 um 21:16 Uhr schrieb Thomas Morley
> <address@hidden>:
> > Am Di., 16. Apr. 2019 um 23:45 Uhr schrieb Aaron Hill
>
> > > Also, I "fixed" the font-size issue by bypassing the font settings
> > > within the grob itself, because simply scaling the glyph results in
> > > thicker lines.  So while font-size is now consistent between the
> > > different grobs, it is unfortunately now a hard-coded value.  I am
> > > uncertain whether this tradeoff would be acceptable.
> >
> > Not sure either, why does Tie has a font-size property at all?
>
> Hi Aaron,
>
> still on the journey to understand all subtleties of your code...
>
> One detail: meanwhile I don't think it's nice hardcoding the
> font-size, looks bad for high or low staff-spaces.
>
> How about looking at staff-space and derive a suitable value from it?
> I.e. in `curve-adjusted-arrow-head´:
>
> [...]
>       (let* ((staff-space (ly:staff-symbol-staff-space curve))
>              ;; reducing fs-from-staff-space a bit looks nicer
>              (fs-from-staff-space (1- (magnification->font-size 
> staff-space)))
>              (grob-font
>                (ly:paper-get-font
>                  (ly:grob-layout curve)
>                  `(((font-encoding . fetaMusic)
>                     (font-size . ,fs-from-staff-space)))))
> [...]

Seems a reasonable approach, but isn't font-size already relative to 
staff-space?

My understanding is that a 20pt staff results in a 5pt staff-space and a 
font of 11pt at font-size 0.  If you change the staff size, fonts will 
scale accordingly (unless you are using something like \abs-fontsize).  
That means that a font-size of 0 will always be 11/5 of the staff-space.

So if the issue is the arrow head being too big, then we should only 
need to set the font-size to a smaller, though still constant, value.

The main reason I was unhappy with hard-coding the size is that for some 
slurs/ties, a user might want a larger arrow head, meaning we should 
ideally be listening to font-size of the grob so each individual curve 
could have its own sized arrow heads.  For instance, PhrasingSlurs, 
which typically extend a larger distance, could use a larger arrow head. 
 But shorter curves read better with smaller arrow heads.  So any 
hard-coded size means all arrows are the same.

Since Ties have a default font-size of -6, a user of this code would 
need to manually override that to something suitable just as they will 
need to provide a value for Slurs and PhrasingSlurs.  Providing they are 
not using the debug annotations, then font-size for any of these grobs 
is unused as a property, so we can party on it without concern.  (Well, 
the only concern is that we document things clearly, lest folks are 
confused why slurs and ties seem to behave differently without the 
overrides.)


-- Aaron Hill