VW 7.5 Glyph question

Hello
I have a question concerning glyph properties: How do I ask VW for the width and height of the glyph
I want to paint? Please see the attached screenshot. Getting the properties of the red bounding box
works, but how do I get the blue box's dimension (which is really the dimensions of the glyph painted)?
If one wants to assemble (rather complicated) math terms, the blue box is essential...

I hope someone can help me; thanks a lot in advance

Mike