void gtk_text_buffer_set_text ( GtkTextBuffer* buffer, const char* text, int len )
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
gtk_text_buffer_insert() directly instead.
len is -1,
text must be nul-terminated.
text must be valid UTF-8.