(This patch is available for firmware versions 2.8.1 - 3.15.0 but is no longer needed in current firmware as the problem described below was fixed in firmware version 3.16.0)
The Kobo firmware has separate built-in stylesheets for the EPUB and KEPUB readers where the default line height is set. There is a long-standing fault in the EPUB stylesheet which causes the line height to be set in proportion to the font size set from the font size slider, instead of in proportion to the final font size on the page as is done in the KEPUB reader. The
`ePub unitless line height` patch fixes this fault.
(This problem might not be very noticable in books which don't use a wide range of font sizes, or where headings don't span multiple lines, or where the publisher forces a fixed line height instead of using the default set by the reader.)
The screenshots below (Glo, 3.2.0) show a page from a
demonstration epub which has three different font sizes set in the book (xx-large, medium, xx-small), with the line spacing adjusted via the slider to suit the medium font size:
1. Unpatched,
2. Patched.