Add callback factory grob::inherit-parent-property

Add callback factory grob::inherit-parent-property

"@var{grob} callback generator for inheriting a @var{property} from
an @var{axis} parent, defaulting to @var{default} if there is no
parent or the parent has no setting."

[MikeSol, 2013-04-17 18:27:05]

Hey, I hadn't seen this. I just finished writing an equivalent patch.  Yours is
better, so keep it.  You can use this for the inherit-X-parent-visibility and
eliminate the inherit-Y-parent-visibility callback, which is cruft and can be
replaced with the X one.

[dak, 2013-04-17 18:45:01]

On 2013/04/17 18:27:05, MikeSol wrote:
> Hey, I hadn't seen this. I just finished writing an equivalent patch.  Yours
is
> better, so keep it.  You can use this for the inherit-X-parent-visibility and
> eliminate the inherit-Y-parent-visibility callback, which is cruft and can be
> replaced with the X one.

I did not actually replace anything because I was not sure of the intent of the
code matching the actual code.

inherit-x-parent-visibility is used only once, so is
inherent-y-parent-visibility.

Apart from the axis discrepancy, the only visible difference is that
inherit-x-parent-visibility has a default of all-invisible, while
inherit-y-parent-visibility has a default of '() and thus can distinguish the
default use, possibly substituting something else.

I was planning to remove _both_ functions here.  The question is what call to
replace inherit-y-parent-visibility with: use rather the X or Y axis parent, and
which default to use.  I am not familiar with the footnote code enough to make
that decision, so I was planning on leaving the actual replacement with you.

I think there are several other rarely used callbacks which would warrant
replacing by a call to grob::inherit-parent-property since that puts the
programmer-interesting information right in define-grobs.scm and does not
scatter it to other files.

[mike7, 2013-04-17 18:59:04]

On 17 avr. 2013, at 21:45, dak@gnu.org wrote:

> Reviewers: MikeSol,
> 
> Message:
> On 2013/04/17 18:27:05, MikeSol wrote:
>> Hey, I hadn't seen this. I just finished writing an equivalent patch.
> Yours is
>> better, so keep it.  You can use this for the
> inherit-X-parent-visibility and
>> eliminate the inherit-Y-parent-visibility callback, which is cruft and
> can be
>> replaced with the X one.
> 
> I did not actually replace anything because I was not sure of the intent
> of the code matching the actual code.
> 
> inherit-x-parent-visibility is used only once, so is
> inherent-y-parent-visibility.
> 
> Apart from the axis discrepancy, the only visible difference is that
> inherit-x-parent-visibility has a default of all-invisible, while
> inherit-y-parent-visibility has a default of '() and thus can
> distinguish the default use, possibly substituting something else.

I think the y callback should have never been added - you should use the x one
instead.  I tested out replacing the y with x and didn't see any visual changes,
so it should be ok.  I think the X parent of a FootnoteItem is the Y parent
anyway.

Cheers,
MS

[dak, 2013-04-18 15:52:30]

Replace a few trivial callbacks with grob::inherit-parent-property and remove
dead code

[dak, 2013-04-18 16:33:58]

Remove goofy quoting of X.  Embarrassing.

[dak, 2013-04-18 17:49:07]

On 2013/04/17 18:27:05, MikeSol wrote:
> Hey, I hadn't seen this. I just finished writing an equivalent patch.  Yours
is
> better, so keep it.  You can use this for the inherit-X-parent-visibility and
> eliminate the inherit-Y-parent-visibility callback, which is cruft and can be
> replaced with the X one.

Would it make sense to rename grob::calc-property-by-copy to
grob::inherit-event-property?  That meshes better with
grob::inherit-parent-property and is more descriptive.