Re: [Lilypond-auto] Issue 3330 in lilypond: bracketify-stencil moves grob's refpoint

[lilypond]

Comment #5 on issue 3330 by address@hidden: bracketify-stencil moves grob's  
refpoint
http://code.google.com/p/lilypond/issues/detail?id=3330

There is also issue 732 involved.  This is a wildly inconsistent mess.  Let  
me state a set of requirements that the bunch of increasingly fragile  
patches tries to meet at the same time:

\markup \parenthesize x should maintain the reference point of x
\markup { a \parenthesize b c } should allow sufficient space for the the  
parentheses
\markup { a \hspace #-1 b } should backspace b over a
\markup { a \null b } should have the same spacing as \markup { a b }
The spacing in a line is solely determined by stencil dimensions.
The reference point of a stencil is solely determined by stencil dimensions.

So if we can't use our X stencil dimensions for figuring out our X  
placement, let's draw the Y stencil dimensions into it:

commit a10833e185f24d63ba084634e24933347e347185
Author: Keith OHara <address@hidden>
Date:   Tue Dec 4 21:34:32 2012 -0800

    stencil.cc: Backspacing stencils are not empty

diff --git a/lily/stencil.cc b/lily/stencil.cc
index a488c59..eb3420d 100644
--- a/lily/stencil.cc
+++ b/lily/stencil.cc
@@ -66,10 +66,13 @@ Stencil::extent (Axis a) const

 bool
 Stencil::is_empty () const
+/* If only one of X- or Y-extent is empty; such a stencil can be useful
+ * for backspacing, as with \hspace #-2, so we do not consider it empty.
+ */

So now if only one extent is empty, it can be used for backspacing, but  
only in one direction.  So now our bracket/paren is backspacing into the  
previous character in a line as its other extent is not empty.

How do we get out of this nuthouse?

Here are a few observations:

a) negative escapements/dimensions are considered valid, so it does not  
make sense to declare one dimension "empty" unless we are talking about the  
untouched +inf,-inf dimension pair.  left > right is not at all the same  
as "empty" when we allow for backspacing material

b) if we distinguish backspacing/non-backspacing alone from the stencil  
dimensions and want \parenthesize x to have the same reference point as x,  
this stencil must not backspace inside of a line in spite of having a  
negative x-min.

c) if \hspace #-3 is supposed to backspace, in contrast, the distinguishing  
difference should be that \hspace #-3 has an _empty_ Y interval (currently  
it is a _non_-empty one).

And empty does _not_ mean min>max like it does with intervals.  People  
still with me on this?

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