Originally Posted by Toxaris
Can you give cases where a ligature should not appear? If I recall correctly, it is only for certain languages like German.
Yes, this is probably a field that is interesting only for some particular languages (German, in my case).
(Just as a general info for non-Germans: In good German typography, it is forbidden to have a ligature across different parts of a compound word. For a word like e.g. auffinden
, which is made from the two morphems "auf"+"finden", one may bind the 2nd "f" with the "i", but one must not bind the two "f". A similar idea might also exist for English, but because English rarely combines words together to a new single word this way, this is probably not relevant here.)
@theducks: Thanks for moving to the right place!
@Jellby: Thanks for pointing me to the Test EPUB! So, obviously at least some readers are able to handle these things correctly. My own device ("Pocketbook Touch"), however, even fails completely at the "Ligatures" chapter of your Test EPUB(s). (Unfortunately this rises more questions as it answers, because this device succeeds in building ligatures for the fonts that I am using for creating my EPUBs, whereas it fails completely at building the ligatures in your Test EPUB. So, there must still be some [font-internal!?] differences that I've not understood so far...)
@dgatwood: Thanks for the suggestion! The good news is: It works (at least with my EPUBs on the Pocketbook Touch), i.e. the combination U+200C U+2060 breaks ligatures (without generating unwanted spaces or line-breaks).
Concerning what the difference might be between these two, I can only guess: Maybe it is related to the full-text-search, maybe the U+2060 breaks the word into two different parts so that the search does not find it, whereas the U+200C should probably not prevent a full-text-search. (But I am not sure about that, and I can even observe for a normal MozillaFirefox on a PC that the full-text-search finds neither a U+200C-separated word nor a U+2060-separated word.)