Re: Adds dimension stencil command to correct with-dimension (issue 12957047)

[dak]

On 2013/08/25 08:22:01, mike7 wrote:
> On 25 août 2013, at 09:15, mailto:address@hidden wrote:

> > A second stencil is not a very good data structure for reserving
space.
> > Skylines are better at this, and we can \once\override 'padding and
> > 'horizon-padding to get padding that follows the outlines of the
> > stencil.
> [...]
> If
> we're going to do that, then we should think of the general problem
we're trying
> to solve.  To me, the general problem seems to be "how can we replace
the
> outline of one shape with that of another?"

No, that is _absolutely_ not the general problem here.  The general
problem is: "how can we replace the outline/skylines of one stencil with
a different outline/skyline?"

Requiring the replacement to be the outline/skyline of an actually
existing stencil is _not_ the general problem.  Why should we need to
create a stencil in the first place if what we want is a horizontal and
a vertical skyline pair?

You create a "filled box" here for \with-dimensions.  That's absurd.
Worse: if you want to compute a skyline _from_ an existing skyline,
there is no way.  You first have to figure out what _stencil_ would have
the kind of skyline you want.

> So far, this question is only ever
> asked in the specific form "how can we replace the outline of one
shape with a
> box?"

No.  With regard to \with-dimensions, the question is how to replace the
outline of one shape with two specified extents.  For pad-x, the
question is how to replace the _horizontal_ (?) skylines with _one_
specified extent calculated from box extents.  Actually, I'd argue that
it would make more sense to shift the horizontal skylines rather than
place an extent.

> But I think if we hardcode the "box" in that question (as both of our
> initial patch sets do), we will lead to the proliferation of multiple
stencil
> primitives for different shapes if the need comes up.

You need a primitive for replacing a subset of four skylines.  And it is
not a primitive but a derived operation, so the backends do not need to
know about it.

> The necessity that comes to mind for the more general solution is the
work I did
> on line spanners, where we often want different skyline padding for
the word in
> the spanner and the line.

"Different skyline padding" is not the same as "skyline of an existing
different stencil".

https://codereview.appspot.com/12957047/