Re: Tweak Slur direction "neutral"

[Jean Abou Samra]

On 30/01/2023 02:20, Ahanu Banerjee wrote:
> When I attempt to change the "direction" property of a slur, whether that is 
> with \tweak or \override, I cannot set the direction to neutral (0). UP (1) 
> and DOWN (-1) work fine, but when setting to 0, I get the following error: 
> 
> "Assertion failed: d, file 
> /home/lily/lilypond-2.24.0/release/binaries/mingw/lilypond/lilypond-2.24.0/flower/include/drul-array.hh,
>  line 56
> Exited with return code 3."
> 
> This is necessary for a function I am creating; Slur.direction has already 
> been set to UP or DOWN earlier in the document, and I need to temporarily set 
> it to neutral while also changing its color. (\once \slurNeutral is not 
> practical here)
> 
> Below is example code that generates the error: 
> 
> \version "2.24"
> \language "english"
> { c' d' \tweak Slur.direction #0 ( e' ) c' }
> 
> Any suggestions?


You can see with

\void \displayLilyMusic \slurNeutral


that \slurNeutral is not equivalent to \override Slur.direction = #0,
but \revert Slur.direction, which reverts Slur.direction to its default
value #ly:slur::calc-direction. So you want

\version "2.24.0"


\language "english"
{ c' d' \tweak Slur.direction #ly:slur::calc-direction ( e' ) c' }


Jean

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