Finally got back around to this... I have since: 1. Given up on trying to have one commit with a tidied-up version of the original author's work, followed by several incremental commits. It's now squashed into a single commit. 2. Expanded the z-range of several quads, so that z results cover a range larger than [0.0, 1.0] 3. Added a quad and test point that are outside of the viewport. 4. Discovered that while not much affects pre-transformed vertices, untransformed vertices (that is, transformed when executing the execute buffer) are affected by the transform/render state, so I added some tests with that in mind.
Note: I believe that when I looked at this a while back, I decided that clearing to a depth value other than 1.0 is more trouble than it's worth for this, and none of the other ddraw1 tests are enabling z-depth testing.