Aligning multiple sized text vertical center instead of baseline with Core Text in iOS.

Question

Is it possible to align multiple sized text by bounding center (of each size) instead of baseline?

I tried CTRunDelegate feature, but it doesn't work. It was possible with CTRunDelegateCallbacks.getAscent and CTRunDelegateCallbacks.getDescent, but the feature doesn't work. Only CTRunDelegateCallbacks.getWidth worked. I succeed to laying out multiple sized text, images, and any objects, but only baseline-alignment supported.