What does the timeline back button do?

If I scroll up a bunch in a topic, the back button appears next to the Discourse post scroll bar. But depending on how far I scroll up, I often have to click the button several times to get back to where I was. I’m having trouble figuring out how the back button works, so if anyone could explain it that would be very helpful.

The blue back button in the vertical timeline (or on mobile, it pops up above the timeline docked at the bottom) takes you to your lowest read position in the topic.

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(I am testing in https://bbs.boingboing.net/t/post-your-pet-or-animal-pics/72032 which I do have read position on, it is post #1983)

However if your lowest read position is at the absolute bottom of the topic, the button will not appear because you can already reach the bottom by pressing the end key or clicking/tapping the bottom of the timeline.

Do note that there has to be room for it to physically appear, so you must scroll up “enough” for it to be a meaningful jump, which depends somewhat on post count.

I can’t repro any problem with “clicking the button several times”. In the above topic every time I click the blue back button on the timeline, I am taken to my last read position.

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Below is a sample workflow for me that shows the issue. Let me know if there’s anything else you want me to try or show you.


Last read position:
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Scroll up a bit to get the back button to appear:
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Scroll up a lot more:
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After clicking the back button once:
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After second click:
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After third click:
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After fourth click:
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Looks like a bug with the site or theme maybe. Can you repro it here on meta? Just pick a long topic you haven’t read before, enter at the top, scroll down a bit and experiment.

The timeline back button should stay docked to the lowest read point, it looks to me like it is inappropriately following scroll for you.

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Ah, yes I am able to reproduce on meta. I tried on a couple topics and couldn’t reproduce at first. But it looks like it might only happen if your last read post is just before the last post.

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Interesting, the tick mark on the timeline is where it’s supposed to be, but the button is incorrect. Perhaps this is an off-by-one bug @eviltrout?

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Any update on this one?

Did you want to assign this to someone else @eviltrout? It does feel like a legit bug to me.

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@maja can you see if you can reproduce and hopefully fix this?

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Fixed in:

https://github.com/discourse/discourse/commit/9a17b196365a1f9a5e88a0f8a36e2e35c56b39bc

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