setSurrounding
Sets surrounding context around the insertion point and preedit string.
This function is expected to be called in response to the signal@Gtk.IMContext::retrieve-surrounding signal, and will likely have no effect if called at other times.
Parameters
text
text surrounding the insertion point, as UTF-8. the preedit string should not be included within @text
len
the length of @text, or -1 if @text is nul-terminated
cursorIndex
the byte index of the insertion cursor within @text.