Hi Andrew,
On 07/15/2016 10:48 AM, Andrew Bernard wrote:
What does the property Beam.positions actually represent? I have seen
code that treats it as the y position coordinates of the end points of
the beam, but I cannot make sense of this. Nor can I make sense of the
manual page for Beam, which gives, as far as I can see, negative
information! -
positions (pair of numbers):
beam::place-broken-parts-individually
Pair of staff coordinates (left . right), where both left and right
are in staff-space units of the current staff. For slurs, this value
selects which slur candidate to use; if extreme positions are
requested, the closest one is taken.
How anybody can read that and understand what it says about beams is
somewhat beyond me. This makes it difficult to program with the
properties in question.
One factor is that the doc strings for these properties are not specific
to one grob. The positions property is (re-)used for many grobs and so
the doc string is very general and often doesn't speak to their use by
particular grobs. The mention of slurs is because of this.
What on earth is ‘beam::place-broken-parts-individually’ in the
context of beam start end vertical positioning? Dear me.
It's a callback function that is called to calculate the value of that
property for this grob. So you have to look at the code in this case to
learn more.
Maybe that helps explain what's going on with the documentation at least.
-Paul
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