Before we start, I'm no font designer. I don't know a lot about fonts. All the information in this post I've gathered from this forum, and/or my own observations.
So I wanted to consolidate as much of the font rules and best practices for the Kobo as I could into one post. Currently this information is scattered about multiple posts over many threads. Here goes:
Font Naming:
The Kobo is very strict about how fonts should be named. The filename of the font files should be as follows
Code:
FontName-Regular.xxx OR FontName.xxx
FontName-Italic.xxx
FontName-Bold.xxx
FontName-BoldItalic.xxx
Where
FontName matches that of the internal font name EXACTLY, and
xxx is
otf OR
ttf
There may be other font naming conventions that are allowed, but this seems to be the most common, and guaranteed to work.
OpenType or TrueType?
This is not actually quite the correct question...
It should be
PostScript Outlines or
TrueType Outlines?, with
OpenType Layout.
By convention it seems that PS outline fonts have an extension of
.otf whereas TT outline fonts have an extension of
.ttf
So which to use? If you wish to use the
Advanced Font Control on the Kobo, then fonts with TrueType outlines should be used. Otherwise it doesn't seem to matter too much.
Kerning:
Adobe RMSDK (epub) seems to make use of the more advanced GPOS for kerning, however, the ACCESS (kepub) only recognizes the "Legacy" kerning features.
If you only read epub, there is no need to add legacy kerning support to the font. Otherwise, for kerning support in kepub, the legacy kerning table is required to be added to the font.
PANOSE:
PANOSE information can be used by applications to identify the characteristics of a font. However in kobo devices.....
Lets just say, that Kobo Nickel gets very confused very easily when it comes to PANOSE. I don't know what parts are problematic, and what is not. I personally completely remove the information (set all fields to 0, or Any), which Nickel seems quite happy about.
Indications of PANOSE problems in Nickel are the font selection list displaying the font in bold and/or italic, rather than the regular variant that it should. This also shows in the page numbers at the bottom of the screen.
Hinting:
Hinting will generally have no noticeable effects. There are some cases it can have a detrimental effect however. This seems to be the case with hand-hinted fonts for the most part. If a font looks ugly/uneven, chances are it could be a hinting, and you should try stripping hints from the font to see if that improves matters.
Hopefully I have covered the main points in this post, and that people find it useful. If anybody has any additions or corrections, please let me know, and I will update the post.