Make per_page default to true to make math lazyloaded

[wafer-li]

PR Checklist

Please check if your PR fulfills the following requirements:

• The commit message follows our guidelines.
• Tests for the changes have been added (for bug fixes / features).
  • Muse | Mist have been tested.
  • Pisces | Gemini have been tested.
• Docs have been added / updated (for bug fixes / features).

PR Type

What kind of change does this PR introduce?

• Bugfix.
• Feature.
• Code style update (formatting, local variables).
• Refactoring (no functional changes, no api changes).
• Build related changes.
• CI related changes.
• Documentation content changes.
• Other... Please describe:

What is the current behavior?

per_page default is false and will render math EVERY PAGE.

What is the new behavior?

per_page default is true and will render math on demand.

That is it will only render those posts with mathjax: true by default

Related: #32 (comment)

How to use?

In NexT _config.yml:

# This is default opiton now
math:
  enable: false
  per_page: true

Does this PR introduce a breaking change?

• Yes.
• No.

[ivan-nginx]

Nice!

[tsanie]

GJ. 👍

And I think it is not a breaking change, because the users' current config will not make the different result, until they change their config.

[ivan-nginx]

It's just optimization.

[ivan-nginx]

And milestone please.

[tsanie]

@sli1989 The code is not changed, and just change the default parameter and docs, the logic works like it before as. And yes, if it is set to true, only the post contains mathjax: true will be rendered with mathjax.

---

original words:
代码没有变动，这次 PR 只是修改了默认选项和文档，逻辑上就和以前一样。如果设置为 true，那就只有含有 mathjax: true 的文章会进行数学公式渲染。

[sli1989]

好吧，还以为改了代码。为啥不考虑删除not呀，为了保持一致性？

[baoang]

正在用这个功能。我觉得单页比较好，因为不是每一篇博客都含有数学化学等公式的，如果每页均要引入mathjax的话，对页面的加载来说是个负担。

目前我的做法就是在含有数学公式的md文件的头部加个mathjax: true

[sli1989]

The question is the logic: per_page: true=not load per page. 😄