Introduce `align_latex` option that allows latex displays aligned left or centered

[klee]

This

%display latex
dm = get_display_manager()   
dm.preferences.align_latex = 'left'  # or 'center' or None
(1+x)^10/(1+x+x^2)

displays the expression flush left, which is the new default.

Motivated by ticket:32859#comment:32.

[klee]

New commits:

​6ef43a0

Introduce display_latex preference

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​5ebf3e5

Fix doctest failures

[git]

Branch pushed to git repo; I updated commit sha1. This was a forced push. New commits:

​a968e39	Introduce display_latex preference
​4fbbeb7	Fix doctest failures

[egourgoulhon]

Sorry for the delay in reviewing!

A few comments:

• the option name display_latex sounds a little too vague and also may - introduce some confusion with the magic %display latex. Wouldn't align_latex be a better name?
• I've tested the new feature with Jupyterlab 3.3 (cf. #32069), it works well!
• Regarding Jupyter (classic), LaTeX outputs are always left-aligned for me (on two distinct Ubuntu 20.04 computers), as discussed at ticket:32859#comment:16 and setting dm.preferences.display_latex = 'center' does not change this...
• Shouldn't 'left' be the default, instead of 'center'? Left-align is the default for SymPy MathJax display in a pure Python 3 notebook and I see no reason to deviate from SymPy policy here. It also better (more readable) for short outputs, like 0.

[klee]

Replying to egourgoulhon:

A few comments:

• the option name display_latex sounds a little too vague and also may - introduce some confusion with the magic %display latex. Wouldn't align_latex be a better name?

I agree.

• Regarding Jupyter (classic), LaTeX outputs are always left-aligned for me (on two distinct Ubuntu 20.04 computers), as discussed at ticket:32859#comment:16 and setting dm.preferences.display_latex = 'center' does not change this...

"left" alignment is forced in the classic notebook. It seems developers decided so. Hence align_latex is only for jupyterlab.

• Shouldn't 'left' be the default, instead of 'center'? Left-align is the default for SymPy MathJax display in a pure Python 3 notebook and I see no reason to deviate from SymPy policy here. It also better (more readable) for short outputs, like 0.

I personally agree. But since "center" alignment has been de facto default in jupyterlab, and "left" alignment is expensive in that the additional code `\displaystyle" is inserted in every output cell, I am not sure if changing the default is a right thing... If you strongly insist, then I would follow. Do you?

[egourgoulhon]

Replying to klee:

• Shouldn't 'left' be the default, instead of 'center'? Left-align is the default for SymPy MathJax display in a pure Python 3 notebook and I see no reason to deviate from SymPy policy here. It also better (more readable) for short outputs, like 0.

I personally agree. But since "center" alignment has been de facto default in jupyterlab,

What do you mean by "de facto default"? I have the impression that, on the contrary, Jupyterlab's default is left-aligned, see e.g. the discussion ​LaTeX display math in output cells should be left-aligned on Jupyterlab github. For instance, in Jupyterlab with Python 3 kernel, the following cells all result in a left-aligned output:

import sympy
sympy.sqrt(2)

from IPython.display import Latex
Latex(r"$\sqrt{2+x}$")

Latex(r"$$\sqrt{2+x}$$")

Latex(r"\[\sqrt{2+x}\]")

Latex(r"\begin{equation}\sqrt{2+x}\end{equation}")

and "left" alignment is expensive in that the additional code `\displaystyle" is inserted in every output cell

Yes this is (one more!) drawback of our "%display latex" magic; instead of relying on Jupyter's native latex display...

I am not sure if changing the default is a right thing... If you strongly insist, then I would follow. Do you?

Despite the \displaystyle burden, I would vote in favor on the left-aligned default, for compatibility both with the display in Sage classic Jupyter and with the default for SymPy and Latex in Jupyterlab. It seems also that users prefer left-aligned, cf. ​https://ask.sagemath.org/question/59775/. Shall we organize a vote on sage-devel?

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​de883c1	Merge branch 'develop'
​45e530a	Rename to align_latex

[klee]

Replying to egourgoulhon:

Replying to klee:

• Shouldn't 'left' be the default, instead of 'center'? Left-align is the default for SymPy MathJax display in a pure Python 3 notebook and I see no reason to deviate from SymPy policy here. It also better (more readable) for short outputs, like 0.

I personally agree. But since "center" alignment has been de facto default in jupyterlab,

What do you mean by "de facto default"?

I meant center alignment is status quo, and is what users got used to in jupyterlab (including myself).

I have the impression that, on the contrary, Jupyterlab's default is left-aligned, see e.g. the discussion ​LaTeX display math in output cells should be left-aligned on Jupyterlab github. For instance, in Jupyterlab with Python 3 kernel, the following cells all result in a left-aligned output:

import sympy
sympy.sqrt(2)

from IPython.display import Latex
Latex(r"$\sqrt{2+x}$")

Latex(r"$$\sqrt{2+x}$$")

Latex(r"\[\sqrt{2+x}\]")

Latex(r"\begin{equation}\sqrt{2+x}\end{equation}")

and "left" alignment is expensive in that the additional code `\displaystyle" is inserted in every output cell

Yes this is (one more!) drawback of our "%display latex" magic; instead of relying on Jupyter's native latex display...

I am not sure if changing the default is a right thing... If you strongly insist, then I would follow. Do you?

Despite the \displaystyle burden, I would vote in favor on the left-aligned default, for compatibility both with the display in Sage classic Jupyter and with the default for SymPy and Latex in Jupyterlab. It seems also that users prefer left-aligned, cf. ​https://ask.sagemath.org/question/59775/. Shall we organize a vote on sage-devel?

I agree. The current default center alignment may be regarded as a defect. No vote in fixing a defect. But perhaps we need to advertise (in release tour?) how to change the behavior for those users that do not like the new default.

[egourgoulhon]

Replying to klee:

I agree. The current default center alignment may be regarded as a defect. No vote in fixing a defect. But perhaps we need to advertise (in release tour?) how to change the behavior for those users that do not like the new default.

OK. Thanks for the changes.

There are 2 doctests failures in src/sage/misc/html.py.

[klee]

Replying to egourgoulhon:

There are 2 doctests failures in src/sage/misc/html.py.

Fixed. Thanks

I preemptively solved merge conflicts with already positively reviewed #33475, by adding it as dependency.

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​ecac525	Fix two doctest failures
​f3d3fda	deTeX documentation title
​528ef65	Use new commands \SL and \PSL
​9187bf1	Fix a glitch
​eff36ec	Fix another glitch
​fe4811c	Fix doctest failures
​7285ad3	Fix more doctest failures
​11ed990	Speed up macro parsing
​7da2b5f	Fix an error in removing $
​74e2696	Merge branch 'trac33475'

[egourgoulhon]

The following notebook cell

%display latex
x

yields

\displaystylex

The argument of \displaystyle should be wrapped into curly brackets.

[klee]

Replying to egourgoulhon:

The following notebook cell

%display latex
x

yields

\displaystylex

In src/sage/misc/html.py, the argument of \displaystyle should be wrapped into curly brackets.

\displaystyle does not take an argument. I put a space after \displaystyle to prevent it from being combined with the following string. I am running doctesting.

[git]

Branch pushed to git repo; I updated commit sha1. New commits:

​3427da0

Put a space after \displaystyle

[egourgoulhon]

Looks good. I've tested the latest version on various notebooks, both with Jupyter and Jupyterlab. Thanks!

[klee]

Thank you!

I will announce this change on sage-devel.