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.
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v3: 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.
https://gitlab.winehq.org/wine/wine/-/merge_requests/8566