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Re: Questions about indentshift

From: Neil Soiffer <NeilS@dessci.com>
Date: Sun, 6 Apr 2014 16:34:19 -0700
Message-ID: <CAESRWkDP34RHPWW4mv0=cxfPoWxzWJkxofP4r2T+v27-8wK=Kg@mail.gmail.com>
To: "Davide P. Cervone" <dpvc@union.edu>
Cc: Neil Soiffer <NeilS@dessci.com>, "www-math@w3.org" <www-math@w3.org>
They aren't the same because indentalign="auto", and MathPlayer (which
generated the image) indents based on the depth in the expression tree at
the point on the alignment. I've attached two images, one with indentalign
equal to  "auto" and one with it equal to "left". With "left", you'll  see
that they are indented the same amount.

As I said in my earlier email, the test would have been clearer if
identalign="left" so auto indenting didn't enter into the mix. I've set the
background to a color in the attached images so you can see the edges.

I hope this is clearer now.

Neil Soiffer
Senior Scientist
Design Science, Inc.
~ Makers of MathType, MathFlow, MathPlayer, MathDaisy, Equation Editor ~

On Sat, Apr 5, 2014 at 12:41 PM, Davide P. Cervone <dpvc@union.edu> wrote:

> Neil:
> Thanks for getting back to me on this, but I'm afraid I'm still confused.
>  I wasn't asking about how indentshift relates to indentalign, but on how
> indentshiftfirst relates to indentshift.  A simplified version of the test
> that I cited is
> <math indentshift="3em" display="block">
>    <mrow>
>       <mi>a</mi>
>       <mspace linebreak="newline" />
>       <mo>+</mo>
>       <mi>b</mi>
>   </mrow>
> </math>
> Here, indentshift is 3em, so I understand that the plus sign will be 3em
> to the right of where it would have been if identshift were 0.  My question
> is where should the "a" be placed?  It should be controlled by the value of
> indentshiftfirst, but the default of indentshiftfirst is "inherited
> (indentshift)".  If I understand this right, the value of indentshiftfirst
> should be the value of indentshift, since there is no setting for
> indentshiftfirst.  So the first line should ALSO be 3em to the right of
> indentalign.
> So what I expect to see if BOTH the "a" and the "+" indented the SAME
> amount (3em).  But in the image for that test, the second line is 3em
> farther to the right of the position of the first line.  (Unless you mean
> that MathPlayer is using the <mrow> around the whole equation to say that
> the line break is nested, so needs to be indented further.  But that would
> mean that the first line would have to be considered as starting outside
> the <mrow>, which seems a bit of a stretch).
> Here is the image from the test:
>  [image: Created by: MathPlayer?]
> The indent shifts for the lines are set to be 3em for the second, 6em for
> the third, and 9em for the fourth.  There is no extra nesting between the
> 6em and the 9em, so the difference between those lines has to be 3em (not
> an adjustment due to nesting), and that means the first line here really is
> 0em.
> I do not see why the first two lines are not at the same indentation.  Can
> you tell me what I am missing?
> For the issue with negative indentshiftlast, I missed the
> indentalignlast="right" in the mstyle at the top of the equation.  Sorry.
>  Now it makes sense.
> Davide
> On Mar 28, 2014, at 3:06 AM, Neil Soiffer wrote:
> First off, I apologize for the very late response. I try to be responsive
> to requests for information, but between a machine crash, a conference, and
> spring break, it didn't happen this time.
> The key to understanding the example is that indentshift is an
> *additional* shift to that specified by the indentalign attribute. That
> attribute defaults to auto, which for MathPlayer (which generated the
> images) indents based on how deeply nested the breakpoint is in the
> expression tree. This gives a visual indication of the grouping of
> expressions. Looking closely at the indentation, I see a bug in the
> algorithm that determines the nesting level, so that doesn't help
> understand the output. This example would have been a better example if it
> had indentalign="left" since it would have made the effect of indentoffset
> clearer.
> The image is also confusing because no indentation is shown for the first
> line. That's likely my fault as I probably made a screenshot and just
> selected the rectangular area around what was drawn. Using a debugger, I
> can see MathPlayer really does indent the first line 3em.
> A negative value for indentshift shifts the line to the left an
> *additional* amount to that specified by the indentalign attribute; in that
> second example, that means 20pts to the left of the right margin.
> Note that MathPlayer (and MathJax?) center block equations, but that is
> not the same as indentalign="center". That attribute would center each
> line. That's not the same as centering the bounding box of the entire
> equation.
> I hope that clarifies the examples,
> Neil Soiffer
> Senior Scientist
> Design Science, Inc.
> www.dessci.com
> ~ Makers of MathType, MathFlow, MathPlayer, MathDaisy, Equation Editor ~
> On Fri, Mar 14, 2014 at 10:29 PM, Davide P. Cervone <dpvc@union.edu>wrote:
>> I was looking at some of the linebreak tests in the MathML3 test suite,
>> and some of them confuse me.  For example,
>> http://www.w3.org/Math/testsuite/build/main/Topics/LineBreak/linebreaking011-indentamount-full.xhtml
>> starts with
>> <math xmlns="http://www.w3.org/1998/Math/MathML" indentshift="3em"
>> display="block">
>> and has some <mi> and <mo> elements then
>> <mspace linebreak="newline"/>
>> According to
>> http://www.w3.org/TR/MathML3/chapter3.html#presm.lbindent.attrs
>> the default for indentshiftfirst is indentshift, and since indentshift is
>> set to 3em, it seems to me that the first and second lines both should be
>> indented to 3em.  But the image of the correct rendering shows the first
>> line not indented, while the second line is indented 3em.  What am I
>> missing, here?
>> A second confusion for me is in
>> http://www.w3.org/Math/testsuite/build/main/Topics/LineBreak/linebreaking010-indentshift-full.xhtml
>> where indenshiftlast is set to -20pt.  The image shows the last line
>> right-aligned (with what appears to be about 20pt of space at the right, so
>> it seems that a negative indentshift is supposed to mean indenting from the
>> opposite side from what indentalign specifies?  There is no mention of this
>> in the spec that I can find.  Can someone clarify the intended meaning of
>> negative indents?
>> Finally, the tests seem to assume a default indentalign of left, but the
>> spec indicates that the default is up to the renderer.  MathJax uses
>> centering by default, so the tests "fail".  it might be good if the tests
>> set indent align explicitly.
>> Davide

(image/png attachment: linebreaking011-indentamount.png)

(image/png attachment: indentalign-auto.png)

(image/png attachment: indentalign-left.png)

Received on Sunday, 6 April 2014 23:34:48 UTC

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