[XeTeX] Unicode-Math in LuaLaTeX and XeLaTeX

[Mathias Schickel]

Dear LuaTeX and XeTeX teams,

it seems that recent versions of LuaLaTeX and XeLaTeX contain some issues regarding the rendering of opentype fonts using the unicode-math package. I have already contacted Will Robertson about these bugs because I supposed the unicode-math package could cause them. According to Will the math rendering is done by the engines and not by unicode-math. This is why I am contacting you now.

The first issue is the usage of the staircase kerning boxes of opentype math fonts. They are obviously not applied in expressions like $f_j$ using LuaLaTeX. The index is rendered too far away from the glyph. If we use XeLaTeX we get the correct output.

The second issue is present in both LuaLaTeX and XeLaTeX. If we have an index together with an exponent like j the index is rendered too high – in fact it is risen compared to the expression that uses an index only. A typical example is $f_n^j$.

I have prepared a minimal example that shows the problems and have attached it and the outputs using the current versions of  LuaLaTeX and XeLaTeX contained in TeXLive.

For the sake of completeness it should be mentioned that ConTeXt using the LuaTeX engine as well does not show any of these issues. This leads me to the conclusion that either LuaLaTeX does not use the most recent version of LuaTeX or that the issues are not caused by the engine itself.

Maybe you have a clue what leads to the bugs I mentioned. I hope they can be solved soon.


Kind regards,
Mathias Schickel




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