Re: Design flaw in Rest_collision

[address@hidden]

On 5 nov. 2012, at 09:26, David Kastrup <address@hidden> wrote:

> "address@hidden" <address@hidden> writes:
> 
>> On 5 nov. 2012, at 09:19, David Kastrup <address@hidden> wrote:
>> 
>>> "address@hidden" <address@hidden> writes:
>>> 
>>>> On 5 nov. 2012, at 06:51, address@hidden wrote:
>>>> 
>>>>> 1) rest->extent (common, Y_AXIS)
>>>>> 2) Rest::height
>>>>> 3) Rest::generic_extent_callback
>>>>> 4) Rest::brew_internal_stencil
>>>>> 5) Rest::glyph_name
>>>>> 6) Staff_symbol_referencer::get_position
>>>>> 7) rest->relative_coordinate (common, Y_AXIS);
>>>>> 8) Rest_collision::force_shift_callback_rest
>>>>> 9) Rest_collision::calc_positioning_done
>>>>> 10) rest->extent (common, Y_AXIS)
>>>> 
>>>> A better way to describe it just to wrap heads around it, with the
>>>> circular dependency underlined:
>>>> 
>>>> Rest extents depend on their stencil.  This stencil depends on
>>>> placement on/off the staff.  Placement may depend on the placement of
>>>> other rests.  To calculate the placement of other rests, we need to
>>>> shift all of them.  The amount of space one must shift depends on the
>>>> extent of the rest.
>>> 
>>> The co-dependent shifts should likely be done by Note_column.  About the
>>> rest dimensions used for that: I'd likely just pick the on-staff glyph,
>>> as the off-staff glyphs just differ by ledger lines IIRC.
>>> 
>>> Keep in mind that this advice is not based on any actual knowledge about
>>> the backend, so it is entirely possible that it is a bunch of nonsense.
>>> 
>> 
>> We're on the same wavelength - this is how rest pure height is
>> calculated.  That's what I've done for now in the code I'm working on
>> to be able to keep working.  It's ugly, tho, as it requires an
>> exception for rests (rest ? use pure height : use height).
> 
> Would the problem not be the same with notes? They depend on things like
> beam scoring, and also have the ledger line situation.
> 

The placement of notes does not depend on beam scoring.  As for ledger lines, 
ledger lines for notes are always a spanner and never built into the glyph.  
Their width is not taken into account in any horizontal spacing equations 
unless approximations are done (see, for example, 
Note_head::include_ledger_line_height).

Cheers,
MS