We made some tests with aqrits' ddraw versions and scaling:
1-st image is war2 windowed mode with your version 154 (based on test2), scaled to 800x600:
2-nd image is war2 windowed mode with aqrit's test4 version scaled to 800x600 (by 3-rd part software as it doesn't support scaling itself).
Interesting thing is it uses such smooth scaling on intel videocards only, but not so smooth on nvidias.
And we can see: test4 support smooth scaling, but your version have some distortions.
is that possible to make your 154 version as beautiful as test4, keeping it based on test2?
Would be great to use such smooth scaling on your ddraw, also being kept compatible with all computers, even with no shader support