Описание тега qtextcursor
The QTextCursor class offers an API to access and modify QTextDocuments.
Text cursors are objects that are used to access and modify the contents and underlying structure of text documents via a programming interface that mimics the behavior of a cursor in a text editor. QTextCursor contains information about both the cursor's position within a QTextDocument and any selection that it has made.
QTextCursor behaves in the same was as a text cursor works in a normal text editor's user interface. It always points either between two symbols of the string, before the first symbol, or after the last symbol. It can also hold a text that was selected.