Default_Editable indicates the editability of text that doesn't have a tag affecting editability applied to it. Typically the result of Gtk.Text_View.Get_Editable is appropriate here. Text: UTF-8 format text to insert. Result: whether text was actually inserted.
Note that the final newline in the buffer may not be deleted; a Gtk_Text_Buffer always contains at least one newline. You can safely include the final newline in the range [Start,End) but it won't be affected by the deletion.
The caller of this function does not own a reference to the returned Gtk_Text_Mark, so you can ignore the return value if you like. Marks are owned by the buffer and go away when the buffer does. Emit the "mark_set" signal as notification of the mark's initial placement.
Return value: the new Gtk_Text_Mark object.
The currently-selected text in Buffer is the region between the "selection_bound" and "insert" marks. If "selection_bound" and "insert" are in the same place, then there is no current selection. Get_Selection_Bounds is another convenient function for handling the selection, if you just want to know whether there's a selection and what its bounds are.
If you want to get the position of the cursor, the simplest way is Get_Iter_At_Mark (Buffer, Iter, Get_Insert (Buffer));
If Tag_Name is NULL, the tag is anonymous, otherwise a tag called Tag_Name must not already exist in the tag table for this buffer.
The "interactive" buffer mutation functions, such as Insert_Interactive, automatically call begin/end user action around the buffer operations they perform, so there's no need to add extra calls if your user action consists solely of a single call to one of those functions.