Notify context that the context surrounding the cursor has changed.
If there's no selection selection_index is the same as cursor_index.
text surrounding the insertion point
the length of text, or -1 if text is nul-terminated
the byte index of the insertion cursor within text.
the byte index of the selection cursor within text.
Notify context that the context surrounding the cursor has changed.
If there's no selection selection_index is the same as cursor_index.