Re: [matplotlib-devel] Different behaviour of mathtext and LaTeX rendering

On Fri, Dec 12, 2008 at 2:22 PM, Michael Droettboom <md...@st...> wrote:

> Darren Dale wrote:
>
>> On Fri, Dec 12, 2008 at 1:06 PM, Michael Droettboom <md...@st...<mailto:
>> md...@st...>> wrote:
>>
>>    Darren Dale wrote:
>>
>>        On Fri, Dec 12, 2008 at 9:46 AM, Michael Droettboom
>>        <md...@st... <mailto:md...@st...>
>>        <mailto:md...@st... <mailto:md...@st...>>> wrote:
>>
>>           Manuel Metz wrote:
>>           > Michael Droettboom wrote:
>>           >
>>           >> There was a discussion on this list around a year ago about
>>           this.  The
>>           >> concern was that not rendering $ as $ would break
>>        (matplotlib)
>>           backward
>>           >> compatibility with scripts that don't care about math at all
>>           but use a
>>           >> lot of dollar signs (e.g. financial plots).  This is one
>>        of the few
>>           >> places where we deliberately broke usetex compatibility in
>>           favour of
>>           >> matplotlib compatibility.
>>           >>
>>           >> That said, it's probably a bug that the escaped dollar
>>        sign in
>>           non-math
>>           >> context is not rendered as a dollar sign.
>>           >>
>>           >> As a workaround "$\$%1.2f$" works with usetex on or off,
>>        with the
>>           >> proviso that it uses math- rather than text-rendering
>>        for the
>>           numbers.
>>           >>
>>           >> Mike
>>           >>
>>           >
>>           > In that case I suggest to note this somewhere in the docs
>>        (and User
>>           > Guide) with three exclamation marks (or is it ???).
>>           >
>>           So there's really two sub-bugs here:
>>
>>           1) '\$8' gives '\$8' in mathtext (well, actually it gets
>>        sent verbatim
>>           to the non-math text renderer, which is a bug).  This,
>>        IMHO, is a
>>           "must-fix".
>>
>>           2) '$8' gives '$8' in mathtext and an error in usetex.
>>         This could be
>>           solved in two ways:
>>
>>           a) document the difference
>>           b) make '$8' give '$8' in usetex as well
>>
>>           I realise b) is technically making usetex accept a string
>>        that is not
>>           normally valid TeX -- but it's not like a user would ever enter
>>           '$8' and
>>           *want* to get a TeX error back.  And usetex strings aren't
>>           perfectly TeX
>>           anyway.
>>
>>           Personally, I'm leaning toward b), because it requires less
>>        mental
>>           effort for the user turning usetex on/off.  And it doesn't
>>        force us to
>>           backtrack on the idea of supporting "$100.00" easily.
>>
>>           But before I commit -- any feedback?
>>
>>         I opposed to b). If we go that route, we can look forward to
>>        advertising usetex as "a latex backend, with familiar,
>>        standard latex markup, except when it isnt."
>>
>>    It's not as bad as that.  '\$8' will still work as in LaTeX as it
>>    always has and as a LaTeX expert would expect it to.  All I'm
>>    proposing is that '$8', which is currently a LaTeX syntax error,
>>    will behave as it does when usetex is turned off.  So it's not
>>    breaking anything that's already valid.
>>
>>    It's a question of which pain is worse, I guess.
>>
>>    The deeper question is -- should usetex even strive to have any
>>    compatibility with standard text?  If not, then I can see your point.
>>
>>
>> http://matplotlib.sourceforge.net/users/mathtext.html advertises \$ as
>> markup for $.
>>
> That's always worked and still worked -- that's not the bug at hand.
>
>> I think it was unwise to accept $ for $ in mathtext in the first place,
>> since mathtext uses tex markup anyway.
>>
> I'm not proposing that at all.  I think we're running into a
> misunderstanding about what I mean by "mathtext" and the scope of the
> proposed change.  By mathtext, I mean "the text between a pair of $ $ when
> usetex is off".  mathtext aims to be TeX-compatible (for a subset).  Regular
> text does not (and in fact has no markup whatsoever).  That last point, I
> believe, is the root of this problem and why reconciling usetex with
> non-usetex may be a losing battle, as you're starting to convince me.
>  usetex is simply not the same thing as regular matplotlib text.
>
> I'll clarify anyway -- but I'm starting to think that unless there is
> someone doing financial plots with usetex that is dying for this feature,
> I'll just leave it.
>
> The bug at hand deals with regular text, not math text.  There has been a
> test in the non-usetex code path for a long time to determine if there is
> any math in the string (by looking for an even number of non-escaped $) and
> allow the simple monetary case to work without needing to escape the $.


Right. I'm not criticizing the work you did on mathtext, which I think is
amazing and could not have done myself. And I forgot that because mathtext
used to be an all-or-nothing enterprise, there was no reason to escape the $
in regular text. Once you made it possible to embed mathtext in a regular
string, I think it would have been better in the long run to require \$, but
the powerful financial interests and their fat-cat lobbyists won the day.


> It used to be impossible to interleave math and regular text in the same
> string and I needed a way to add support for interleaving without breaking
> existing usage, and without requiring an explicit flag saying "my string has
> math".  It's not perfect -- if you want to have math *and* use a dollar
> sign, you still have to know what you're doing and do some sort of escaping.
>  But it's served well for over a year.
>

Thanks for reminding me, I forgot the context.


>
> The question, then, is whether to bring those smarts over to usetex, and
> whether any sort of usetex/non-usetex consistency is a goal.
>
>>
>> If we went with b), how sure are you that you can identify when a dollar
>> sign is intended and when mathmode is intended? Does "$A-$100+B*$200$" mean
>> $(A-100+200B) or A-100+200 or ..., I know this is an unlikely example, I'm
>> just trying to think of the unintended consequences of circumventing one of
>> the least buggy pieces of software in existence (I mean tex, not latex).
>>
>>  It means [A-]100+B*[200] (where the contents in brackets is math,
> otherwise text), just like in TeX.  An example where there is ambiguity is
> when you have an odd number, such as "$A-$100+B$". In TeX, that's a syntax
> error, but with my proposed change (and in non-usetex already) it would
> render as "$A-$100+B$".  So at best, it's a "does the right thing", and at
> worst is a "silent fail", depending on your perspective.
>
> Hope that clears things up.
>


What I would prefer is to raise a deprecation warning when an odd number of
dollar signs are encountered, giving people time to learn to escape their $
and modify their code. I wonder how disruptive this would be to people using
mpl for finance? If that is unacceptable, I guess the best solution is as
you propose, but maybe usetex should issue a warning that it has modified
the string rather than strictly interpret it.

Do you know if there are any other inconsistencies between the text/mathtext
markup and latex?