To clarify -- is the problem you're reporting that C₅₀H₇₀ visually appears as ₇₀H₅₀C in the PDF?

yes!it changes

C50H70

to

70H50C

also <big> has this problem

volker.haas wrote:

This bug is part of a more general problem with right-to-left text:

The pdf framework we are using (reportlab) breaks a paragraph with "inline styles" like <sub>, <sup>, <big>, ... into fragments for further processing.
The bidi algorithm is then applied to the individual text fragments.

I don't really know how to fix this problem...

ab3550 wrote:

till will be solved for rtl wikis would you please disable it?
it disorganized the texts that has formula like
http://fa.wikipedia.org/wiki/%DA%A9%D8%B1%D8%A8%D9%86_%D8%AA%D8%B1%DB%8C_%D8%A7%DA%A9%D8%B3%DB%8C%D8%AF
also please tell me which part of The pdf framework (python file) works with "inline styles". i will ask form some of my friend who works in rtl text rendering

volker.haas wrote:

So the situation is the following:

Directionality for styled left-to-right text in right-to-left Wikis is currently broken.

In order to fix the directionality I would need to disable styling altogether and all fontswitching.

-> It doesn't seem sensible for me to break two features in order to fix another feature a little bit.

I am really sorry, but I doesn't seem to make sense to further try improving the PDF output for right-to-left wikis with the current rendering engine.

most of the bugs are solves except
<div dir="ltr" class="mw-content-ltr">

As already announced in Tech News, OfflineContentGenerator (OCG) will not be used anymore after October 1st, 2017 on Wikimedia sites. OCG will be replaced by Electron. You can read more on mediawiki.org.