Re: Combining NoteHead and Stem stencils for rotation

[address@hidden]

On Mar 29, 2011, at 9:25 AM, David Kastrup wrote:

> address@hidden writes:
> 
>> Hey all,
>> 
>> I'd like to rotate a note head and its stem in one fell swoop.
>> 
>> This seems rather nightmarish to do.  I can envision two solutions:
>> 
>> (1) Combine the stem stencil with its notehead stencil and then make
>> the notehead transparent.  Then, rotate this uberstencil.
>> (2) Do trig on the stem to translate it after having rotated the
>> notehead (or vice versa).
>> 
>> Both of these options seem not easy, but option 2 seems more feasible.
>> In order to do this, though, I'd have to spend a fair bit of time
>> doing the math and work with different unit systems for X and Y (I
>> think).
>> 
>> Before I start on this, can anyone think of a quick & easy way to do
>> this rotation?
> 
> 2 seems rather trivial.  Note that rotation about (x,y) is the same as
> subtracting (x,y), rotating about (0,0), and then adding (x,y).  So it
> should be easy enough, given the rotation of one element, to make
> another rotate in a shifted coordinate system.

The difficulty I had with this is that I get the sense that noteheads cannot be 
separately translated.

#(define (goo grob)
  (let* ((refpy (ly:grob-common-refpoint grob (ly:grob-parent grob Y) Y))
         (coord-y (ly:grob-relative-coordinate grob refpy Y))
         (rad (+ coord-y 2.5))
         (angle (degrees->radians 15))
         (x-trans (* rad (cos angle)))
         (y-trans (- (* rad (sin angle))))
         (stencil (ly:note-head::print grob)))
         (ly:stencil-translate (ly:stencil-rotate stencil 15 -1 -1) (cons 
x-trans y-trans))))   

\relative c' {
\override Stem #'stencil = ##f <\tweak #'stencil #goo d \tweak #'stencil #goo f 
\tweak #'stencil #goo a>8
}

You'll see that the three noteheads never translate in their X dimension.  I'm 
suspecting that the note column tries to keep them in line.  Is there a 
workaround for this without messing with stencil extents?

Cheers,
MS