Looks like that nsIPhonetic is not used anybody (including add-ons and BlueGriffon). IIRC, it was used for a11y to retrieve phonetic of active composition string. However, the implementation was really hacky: https://searchfox.org/mozilla-central/rev/224cc663d54085994a4871ef464b7662e0721e83/editor/libeditor/EditorBase.cpp#2526,2528-2532,2537-2539 So, I guess that a11y stop using it with some reason (e.g., giving up to implement it or using new API on some platforms).

Marking this instantly as dev-doc-complete, as we never documented this on MDN anyway, therefore no docs work is needed.

Comment on attachment 8866236 [details] Bug 1363278 Get rid of nsIPhonetic and HTMLInputElement.phonetic https://reviewboard.mozilla.org/r/137864/#review141036 ::: dom/html/HTMLInputElement.h (Diff revision 1) > > class HTMLInputElement final : public nsGenericHTMLFormElementWithState, > public nsImageLoadingContent, > public nsIDOMHTMLInputElement, > public nsITextControlElement, > - public nsIPhonetic, Thanks! This reduces the size of input elements by 4 or 8 bytes (32bit vs 64bit systems).

Pushed by masayuki@d-toybox.com: https://hg.mozilla.org/integration/autoland/rev/57330642868c Get rid of nsIPhonetic and HTMLInputElement.phonetic r=smaug