Call for testing: Stretching of Operators
Frédéric Wang
As some of you probably know, there is undergoing work on MathML
stretching. For the impatient, I set a TryServer here:
https://build.mozilla.org/tryserver-builds/fred...@free.fr-try-08c872a8d318/
If I don't miss anything, the list of bugs reported by users and related
to stretchy operators is:
1) Bug 414294: double vertical bar
2) Bug 416140: underbraces and overbraces
3) Bug 416065: tilde, check and hat accents
4) Bug 464592: square root rendering too large in MathML
5) Bug 491370: right and left angle brackets
6) Bug 516292: triple arrow
7) Bug 518330: large operator
and there are essentially three suggestions that have been made to fix
these bugs:
I) Bug 407101: Complete support for STIX fonts
II) Bug 414277: Use a scale transform to improve stretching
III) Bug 534970: Update MathML Operator Dictionary
A patch has recently been pushed for I), fixing most of the issues 1-7)
above when the user has STIX fonts installed. I've long been stuck on
II) but a recent upgrade of the Cairo library seems to have solved my
problem. The current set of patches for II) and III) fixes all the
issues 1-7) above.
Unfortunately, the patch for II) possibly makes new bugs appear: some
operators may stretch in situation where they should not, because of
errors in our Operator Dictionary or in the way we determine the
Operator Form. Normally, I've fixed all the issues I'm aware of, but it
is possible that there are remaining ones. I would like to be sure that
it is not the case, before asking for a review. That's why I've set a
TryServer and ask people to test on "real-world" MathML markup. Please
check improvements and report any unexpected behaviors. It could also be
interesting to test *without* STIX fonts installed.
Some precisions on 7). MathML3 changed the properties of large operators
(such that ∑ or ∫) to have the same behavior as TeX, i.e.
they are only drawn larger, not stretched vertically. This is also what
we are going to do and the size of the largeop operator are increased by
a factor of sqrt(2) in display mode. I don't know if this factor is
ideal, maybe 2 is better for integrals. The patch for II) will also give
more flexibility to people, allowing them to enable/disable stretchy or
largeop attributes as they want (on the trunk version, only
stretchy="false" or largeop="false" have an effect).
Some precisions on the way the patch for II) works. Our current support
for stretchy char is based on two methods: either using "char variants"
of different sizes or assembling several glyphs to build "composite
chars". Using these methods, we try to find a character as near as
possible to the desired container size. With the patch for II), we apply
an additional scale transform to this character, so that it exactly fits
the container size. Of course, scaling is not the same as stretching: if
the aspect ratio of the scaled character is too different from the
original one, then we may obtain some unelegant deformation. So the idea
is the following: if we are already able to stretch very closely to the
container size, then the scaling gives a slight improvement (consider
for instance the rendering of radical in the test 13 of torture test) ;
if we don't support stretching by the classical methods (for instance
6), for triple arrows) or if the user does not have the appropriate
fonts installed, then the scaling is considered an acceptable fallback
to use for stretching.
Fr�d�ric Wang
Frédéric Wang
On 14/05/2010 19:13, Fr�d�ric Wang wrote:
> Hi folks!
>
> As some of you probably know, there is undergoing work on MathML
> stretching. For the impatient, I set a TryServer here:
>
> https://build.mozilla.org/tryserver-builds/fred...@free.fr-try-08c872a8d318/
>
>
New builds, that should improve the rendering of integral symbols:
http://ftp.mozilla.org/pub/mozilla.org/firefox/tryserver-builds/fred...@free.fr-2c8ac775ab39
--
Fr�d�ric Wang.
Website <http://www.maths-informatique-jeux.com/> - Weblog
<http://www.maths-informatique-jeux.com/blog/frederic/>
Frédéric Wang
support for some variants of integral symbols.
http://ftp.mozilla.org/pub/mozilla.org/firefox/tryserver-builds/fred...@free.fr-ed9b166431cb/