Undoes the last user action which modified the buffer. Use
gtk_source_buffer_can_undo() to check whether a call to this
function will have any effect.
Actions are defined as groups of operations between a call to
gtk_text_buffer_begin_user_action() and
gtk_text_buffer_end_user_action(), or sequences of similar edits
(inserts or deletes) on the same line.
Undoes the last user action which modified the buffer. Use gtk_source_buffer_can_undo() to check whether a call to this function will have any effect. Actions are defined as groups of operations between a call to gtk_text_buffer_begin_user_action() and gtk_text_buffer_end_user_action(), or sequences of similar edits (inserts or deletes) on the same line.