Emitted when the input method wants to delete the context surrounding the cursor.
If offset is a negative value, it means a position before the start of the selection, or before the cursor if there is no
selection. The text to be deleted can include part of the selection. If n_chars is 0, nothing is deleted and the cursor is
moved by offset.
Both offset and n_chars are counted in UTF-16 code units, not in characters: a character outside the Basic
Multilingual Plane, like most emoji, counts as 2. Note that the indexes passed to
notify_surrounding are in bytes instead.
| offset |
the offset of the text to be deleted from the start of the selection, in UTF-16 code units |
| n_chars |
the number of UTF-16 code units to be deleted |