`mirror: "all"`: spurious ticks
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Description
The documentation of mirror states that:
If "all", axis lines are mirrored on all shared-axes subplots. If "allticks", axis lines and ticks are mirrored on all shared-axes subplots.
I.e., from what I gather mirror: "all" should not put any tick marks but merely draw a line. Presently, however, it does put tick marks on the mirrored axis of the first subplot (or even solitary plot).
Previously, a variant of this was noted in #4136 where mirror: "all" would behave like mirror: "allticks". This was addressed in #4140, but the fix seems only to have addressed part of the issue, however. Specifically:
| Example | Behavior | |
|---|---|---|
| Before #4140 (v1.49.3) | https://codepen.io/thchr/pen/yLbpowE | Ticks on all mirrored axes |
| After #4140 (v1.49.4 and later) | https://codepen.io/thchr/pen/qBmpXge | Ticks on mirrored axis of first subplot |
What I thought expected behavior would be is this (i.e. tick on no mirrored axis; only the left-most non-mirrored y-axis of the first subplot):

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Research direction
Reproduce the behavior using the linked CodePen examples and compare mirror: "all" with mirror: "allticks" on shared-axis subplots. Trace the axis-mirroring behavior responsible for the first subplot, then verify that mirror: "all" draws mirrored lines without tick marks while the expected non-mirrored axis retains its ticks.
Written by the indexing model from the issue text.
Assessment
- Tech stack
- javascript
- Domain
- data-visualization
- Issue type
- Bug
- Difficulty
- 3/5
- Estimated time
- 1-2 days
- Activity status
- Stale
- Clarity
- Mostly clear
- Newbie friendliness
- 45/100