Re: Inserting a grob into a Spanner NOT at last position

[Joe Neeman]

On Tue, 2010-03-16 at 15:46 +0100, Reinhold Kainhofer wrote:
> In the Figured_bass_engraver, I have a BassFigureAlignment spanner, where 
> Align_interface::add_element is used to append new figures. However, with 
> extenders turned on, it happens frequently that a new figure needs to be 
> inserted into the spanner at some fixed position (e.g. the beginning). 
> 
> AFAICS, Align_interface::add_element always appends the newly inserted grob 
> and places it at the bottom. I could not find any way how to insert a grob at 
> a specified position (e.g. at the beginning rathen than at the end, or before 
> another specified grob).
> 
> AFAICS, Align_interface::add_element basically propagates the new grob to 
> Pointer_group_interface::add_grob, where it is appended to the Grob_array 
> (stored as the 'elements object of the spanner). 
> 
> So, how can I insert a grob at some other position?
> 
> 1) Shall I simply append it using add_element and then try to extract the 
> 'elements object and manually try to reorder afterwards?

This is more or less how alignAboveContext is handled (in
vertical-align-engraver.cc). If you moved that code to Align_interface
then you could reuse it.

Cheers,
Joe