setText
Deletes current contents of @buffer, and inserts @text instead. This is automatically marked as an irreversible action in the undo stack. If you wish to mark this action as part of a larger undo operation, call method@TextBuffer.delete and method@TextBuffer.insert directly instead.
If @len is -1, @text must be nul-terminated.
Parameters
text
UTF-8 text to insert
len
length of @text in bytes