Maximum length of 'kern' table supported in .ttf?

[Rob T]

Hi,

I am trying to use Adobe Source Serif in WPS Office on Linux. I notice that it 
ignores kerning pairs in the .otf version. In the .ttf version it also ignores 
kerning pairs. This is because WPS doesn't support GPOS kerning.
However, if I open either of the original fonts in fontforge and export as .ttf 
with a 'kern' table then kerning is activated in WPS Office.
I notice that there are 200,000 kern pairs in 15 subtables in my generated 
fonts. What is the limit of entries that freetype can handle?
thanks
Rob