gjc@eileen.mga.com (George J. Carrette) (09/15/89)
From the perspective of another longtime lispmachine user and system implementor, and also a developer who used the VAX/VMS VWS/UIS I can understand the advantages of NOT having backing store. There are many abilities that shine in X that I would not trade for a mere backing store. And the proof of the pudding for me is the XTURTLE example (originated at DIGITAL perhaps?), where the implementor keeps his own backing store by invoking all Xlib graphics commands on both the WINDOW and the PIXEL-ARRAY. It is far better to buy two cheap items to get a job done than it is to buy one expensive item with a lots of extras that end up costing you log(n)*n, n^2, or worse in overall system performance in any PRACTICAL implementation. What screws me every day is not having stack-groups to deal with the limitations of obvious compromises like XT-APP-ADD-WORK-PROC and XT-APP-ADD-INPUT. That is, when I use VMS why do I have to live with designed-in limitations based in the lack of modern functionalities of Unix? But that is LIFE, I understand why and can deal with it without complaining too much. -gjc