The header controls are a bit weird. It seems v6 returns 0 for this, but unlike v5 it has its own IAccessible implementation. Since Wine doesn't have that yet, and we can't easily change behavior based on version, I think it makes sense to return a value.
-- v4: comctl32/tests: Remove individual OBJID_QUERYCLASSNAMEIDX tests. comctl32: Implement OBJID_QUERYCLASSNAMEIDX for updown controls. comctl32: Implement OBJID_QUERYCLASSNAMEIDX for treeviews. comctl32: Implement OBJID_QUERYCLASSNAMEIDX for trackbar controls. comctl32: Implement OBJID_QUERYCLASSNAMEIDX for tooltips. comctl32: Implement OBJID_QUERYCLASSNAMEIDX for listviews. comctl32: Implement OBJID_QUERYCLASSNAMEIDX for hotkey controls. comctl32: Implement OBJID_QUERYCLASSNAMEIDX for Animate controls. comctl32/tests: Add general tests for OBJID_QUERYCLASSNAMEIDX.