Adds the mark at position where.
The mark must not be added to another buffer, and if its name is not null then there must not be another mark in the buffer with the same name.
Emits the [[email protected]:GtkTextBuffer:mark-set] signal as notification of the mark's initial placement.
| this |
a `GtkTextBuffer` |
| mark |
the mark to add |
| where |
location to place mark |