Currently the display 'Keyboard' and 'History' have the same fixed height no matter how much height the Qalculate window has, and they both can't be done at the same time. Viewing of the display 'Keyboard' along with 'History' should be able to be done simultaneously. I see no reason why one should exclude the other.
How about putting the 'History' above(or optionally below?) the display 'Keyboard, and have the 'History's' height vary based on how much vertical space Qalculate has?
The display 'Keyboard' having a fixed height seams fine right now to me, but not the 'History'. It's the 'History' that should change in vertical size based on Qalculate's vertical size not the vertical space for the last answer.