How to implement auto-complete for text editor on Qt 5?

Question

Qt

Good afternoon, I'm writing an IDE for Qt 5 and I ran into the fact that I can't implement auto-complete. Help me please!

Answer 1

doc.qt.io/qt-5/qcompleter.html

Answer 2

What does "can't implement" mean? Do not know how to insert a drop-down list in the text? Don't know how to add pictures to the list? Do not know how to compose the contents of the list?
In general, if you have such questions, it's too early for you to write an IDE.