Re: Help with espressivo adjustments

[Janek Warchoł]

This excellent!  it's premium material for extending manual - could
you post it as a patch?  If you don't have time to texinfo it, let's
at least add an issue to the tracker.

Janek

2013/4/13 Thomas Morley <address@hidden>:
> 2013/4/12 SoundsFromSound <address@hidden>:
>> Thomas:
>>
>> That works beautifully!
>>
>> When you get a free moment, could you please break down that code for me
>> piece by piece so I can understand how I may be able to edit it in the
>> future, if need be (for further adjustments / size changes)?
>>
>> Thank you again,
>>
>> Ben
>
> Ok, I'll try, though, please remember I'm not a programmer. My
> explanations may be not complete.
>
> I decided to develope the code in step by step manner.
> (You'll notice that in the end the code is changed a bit, compared
> with my previous post.)
>
> I) PROBLEM
> With { f\espressivo } the "espressivo"-sign (i.e. every small hairpin)
> should become longer, but not higher.
>
> II) possible SOLUTIONS
> a) create a new stencil
> b) scale the default-stencil in direction of X-axis
>
> III) THOUGHTS about II)
> Solution a) is doable. But will result in a higher coding effort.
> Solution b) is cheaper. It's disadvantage is that it will not print
> acceptable results in all cases.
> (Although you may not know this before you've tried :) )
> Result: choose solution b)
>
> IV) CODING
> i) If you want to manipulate the default-stencil you have to find/get it.
> Looking in the IR
> http://lilypond.org/doc/v2.17/Documentation/internals/script
> shows:
>   stencil (stencil):
>       ly:script-interface::print
>
> Let us test if it is correct.
> To be sure that I affect the correct grob, I often use colors. There
> is a predefined function, which does so:
> From IR
> http://lilypond.org/doc/v2.17/Documentation/internals/scheme-functions
>   Function: ly:stencil-in-color stc r g b
>       Put stc in a different color.
>
> This will result in:
>
> colorDefaultStencil =
> \once \override Script #'stencil =
>   ;; `lambda´ starts a procedure, it's argument is `grob´
>   #(lambda (grob)
>      ;; In `let´ local variables are defined.
>      (let ((stil (ly:script-interface::print grob)))
>      ;; The procedure returns the colored default-stencil:
>      (ly:stencil-in-color
>        stil
>       1 0 0)))
>
>      { \colorDefaultStencil f''\espressivo }
>
> Fine, works.
>
> ii) Wanting to get a scaled stencil, we have to use
>   Function: ly:stencil-scale stil x y
>       Scale stil using the horizontal and vertical scaling factors x and y.
> from the same IR-chapter.
>
> Resulting in:
>
> scaleColorDefaultStencil =
> \once \override Script #'stencil =
>   #(lambda (grob)
>      (let ((stil (ly:script-interface::print grob)))
>      (ly:stencil-in-color
>        (ly:stencil-scale
>          stil
>          ;; 1 is the neutrat element with ly:stencil-scale
>          ;; i.e. scaling with: 1 1 (for x- and y-axis) returns a not (visible)
>          ;; changed stencil.
>          2 1)
>       1 0 0)))
>
>      { \scaleColorDefaultStencil f''\espressivo }
>
> Well, apart from the color that seems to be the desired output.
>
> iii) Though, there are some problems.
>
> Look at:
>
>      { \scaleColorDefaultStencil <f'' a''>_\espressivo ^\fermata }
>
> a) The fermata is scaled, too.
> b) Typing the command before and \espressivo after the note(s) is annoying.
>
> Solution for both: use tweak!
>
>      {
>              <f'' a''>
>              -\tweak #'stencil
>              #(lambda (grob)
>                       (let ((stil (ly:script-interface::print grob)))
>                       (ly:stencil-in-color
>                         (ly:stencil-scale
>                           stil
>                           2 1)
>                        1 0 0)))
>              _\espressivo ^\fermata
>      }
>
> Does what we want, though, typing this isn't nice.
>
> Ok, let's define a variable and use it with the tweak.
>
> With some copy/paste we get:
>
> #(define longer-script  ;;[1]
>   (lambda (grob)
>           (let ((stil (ly:script-interface::print grob)))
>           (ly:stencil-in-color
>             (ly:stencil-scale stil 2 1)
>             1 0 0))))
>
>      {
>              <f'' a''>
>              -\tweak #'stencil #longer-script
>              _\espressivo ^\fermata
>      }
>
> Works fine, though the scaling values are hard-coded and there might
> be the possibility to avoid typing of
>    -\tweak #'stencil #longer-script
>
> First, let's introduce some variables in `longer-script´ for scaling
> in x- and y-axis:
>
> #(define (longer-script x y)
>   (lambda (grob)
>           (let ((stil (ly:script-interface::print grob)))
>           (ly:stencil-in-color
>             (ly:stencil-scale stil x y)
>             1 0 0))))
>
> Second, to reduce typing-effort we define an event-function:
>
> scaleScript =
> #(define-event-function (parser location x-val y-val)(number? number?)
> #{
>         \tweak #'stencil #(longer-script x-val y-val)
>         \espressivo
> #})
>
> { <f'' a''>_\scaleScript #2 #1 ^\fermata }
>
> Works as expected, fine!
>
> iv) Clean up
> - We only want scaling in x-direction: Let's hardcode y-scaling in the
> event-function.
> - Delete the color.
>
> V) THE FINISHED CODE
>
> \version "2.17.15"
>
> #(define (longer-script x y) ;; [2]
>   (lambda (grob)
>           (let ((stil (ly:script-interface::print grob)))
>           (ly:stencil-scale stil x y))))
>
> longEspressivo =
> #(define-event-function (parser location x-val)(number?)
> #{
>         \tweak #'stencil #(longer-script x-val 1)
>         \espressivo
> #})
>
>      { f''^\longEspressivo #2 _\fermata }
>
> VI) REMARKS
> [1] Coding
>     #(define (longer-script x y)
>       (lambda (grob)
>        ...
> or
>     #(define ((longer-script x y) grob)
>        ...
> is nearly the same. It's more a matter of taste.
> Sometimes the use of `lambda´ is regarded the more elegant method.
>
> [2] It's possible to affect every grob with this definition, as long
> the default-stencil is
> `ly:script-interface::print´
>
> In general:
> Explaining/commenting is more work than coding itself.
> That's the reason why our documentation is sometimes not on the same
> level as the functionality of the program. ;)
>
> There might be special, more complex cases, where the code above will not 
> work.
> I omitted any comment about these. This would belong to a new thread.
>
> VI) LAST
> I didn't explain predefined guile-procedures/macros etc
> i.e. "define", "let", "number?"
> (or at least not very verbose)
> If you're interested to dive in deeper, you may refer to the
> guile-manual and/or one of the scheme-tutorials available online.
>
>
> I hope I forgot nothing important and did not to many typos. ;)
>
>
>
> Cheers,
>   Harm
>
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