Inserts @len bytes of @text at position @iter. If @len is -1,
@text must be nul-terminated and will be inserted in its
entirety. Emits the “insert-text” signal; insertion actually occurs
in the default handler for the signal. @iter is invalidated when
insertion occurs (because the buffer contents change), but the
default signal handler revalidates it to point to the end of the
inserted text.
Inserts @len bytes of @text at position @iter. If @len is -1, @text must be nul-terminated and will be inserted in its entirety. Emits the “insert-text” signal; insertion actually occurs in the default handler for the signal. @iter is invalidated when insertion occurs (because the buffer contents change), but the default signal handler revalidates it to point to the end of the inserted text.