How to center a text printed with glutBitmapCharacter ?

Hi everybody.

In fact, I print characters in 3D using glutBitmapCharacter ang glRasterPos
And Whan I move the camera, the text turn with it and scale in order to always be printed with the same number of pixels on the screen.

For exemple “test”

The text turn around the point precised in glRasterPos and is fixed with the first t. So In fact, it turns arround this.

And I would like the text to turn around the middle of the word.

How can I do that?

Thanks in advance