Running text & slow drawText

[KL-7]

Hi.
I want to implement a running text line for typing trainer. I need it to be smooth, so I cant use QLineEdit and move text by one character.
So I wrote my own widget which draw text with QPainter::drawText and move every character aproximately in 10 steps with 10 milisecond interval.

It works quite good, but drawText seems to be a quite slow operation.
When I use 35 font size it works perfect, but when I use smth like 55-75 (the text to draw become bigger) my widget cant keep pace with me (I type about 60wpm) on my old computer (and CPU usage jump from 20% to 98%).

So I need to make it faster. Are there any better (faster) ways to draw text?