
Ask HN: Details behind years old Windows taskbar bug? - MzHN
There is a long standing bug in Windows, where the hover state on taskbar items - highlight and a window preview - gets stuck after having the computer run for a while, as if the taskbar never notices the cursor leaving it.<p>I&#x27;ve had this bug on every single Windows version since Windows 7, on every single installation and every single Windows PC I&#x27;ve used actively.<p>Along the years I&#x27;ve seen people suggest all kinds of workarounds for this, but I&#x27;ve seen none that do more than temporarily fix the issue.<p>This bug has intrigued me ever since I noticed it being consistent across versions, and most recently I checked if it still applies to Windows 10 Anniversary Update, which it does. Why is it so persistent? Why did it survive the &quot;should-not-call-it-metro&quot; changes to the explorer shell?<p>Since there&#x27;s often interesting discussion and insight on obscure bugs in Hacker News, does anyone have any insight on this? Has anyone ever debugged it?
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adzm
It might be related to the TrackPopupMenu on notification tray workaround,
where one must set themselves to the foreground window and post WM_NULL or
other message in order for the window to be properly dismissed.

However that one in particular iirc has to do with the way input is handled
among threads, and how Windows is careful with how activation / focus gets
passed among processes.

Since the taskbar needs to do various things without taking input focus or
capturing the mouse etc, I would assume the bug has to do with managing this
obscure behavior, and missing a notification (or some obscure race condition?)
that results in the taskbar not transitioning to the non-hover state.

Outside the taskbar you can often see these bugs in situations such as click,
hold the mouse, then move outside of the window or have focus switched. Many
times the capturechanged events or activation events do not end up handled
properly -- trying to do all this without capturing the mouse or input is even
more difficult, though I presume a simple timer would suffice.

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AshleysBrain
If you can't reproduce it reliably and it's kind of rare... isn't that enough
to explain it? :P First thing you need in a bug report is a reliable way to
get it to happen!

Also having read Raymond Chen's "Old New Thing" blog for a while, it's very
common that some third party software/extension does something insane with the
desktop window and breaks things. It could be something like that. Can you
reproduce it on a completely empty fresh install of Windows?

~~~
MzHN
I am currently on a fairly fresh install of Windows 10 (past week or so), but
I do have some of my dev environment installed, so not completely clean. It
started happening pretty soon as always for me.

I'm starting to think it may have something to do with the way some people
interact with the UI, as some people do not get it at all and some, like me,
get it often.

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SippinLean
Related SuperUser question (from 2009) including demo and workaround:

[http://superuser.com/questions/61833/windows-7-taskbar-
icon-...](http://superuser.com/questions/61833/windows-7-taskbar-icon-
highlight-sticks)

~~~
MzHN
Also notable that these questions still pop up for Windows 10 even now. When
they had the UserVoice set up for Windows 10, this bug was there as well. I
think the UserVoice is gone now though.

One other "bug" I wish they would fix is when you change virtual desktops, the
taskbar items reset, apparently, to the order the windows were opened in.
Messes me up really bad as I keep the windows in specific order.

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ungzd
I've seen pressed/depressed button state bug periodically in older versions of
Windows (up to XP it seems). Sometimes multiple buttons in taskbar appeared in
pressed state (should be one which is active).

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Vexs
Weird, I've had all sorts of bugs happen to me, but I've never actually seen
this particular one happen across 4 or so systems.

As to your question, I figure it's the same as anything else in windows,
legacy code. One library gets stacked on top of another, then another, and
when the UI pulls from it, it drags up bugs from the entire stack.

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stinos
How exactly does one reproduce this?

~~~
cocotino
I think it has happened to everybody, but I can't reproduce it reliably. It
happens to me at random, if I don't reboot the computer for days it will
always appear.

You can kill explorer.exe to fix it.

~~~
nilved
I left my Windows PC on for years at a time and didn't notice this. I wouldn't
be surprised if it was non-deterministic.

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mintplant
There's a similar bug where a taskbar set to auto-hide will stop, well, auto-
hiding. The recommended solution is to pop open Task Manager, find
explorer.exe, and restart the process.

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friendzis
I have seen similar bug in probably all versions since XP, not sure about 10
though. Sometimes a hover-tooltip would not disappear after moving mouse out
of taskbar or system tray item.

As I am using beefier hardware it gets more difficult to reproduce, but the
general pattern is oversaturating I/O: have multiple memory hungry
applications swapped out and try to bring them all back.

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kabdib
Drives me bonkers every few weeks. I set the task bar to "auto hide" and then
it decides, at random, to never hide, pushing my Emacs mode line and the
bottom few lines of text in the editor down under that useless thing.

I usually reboot at that point. This issue has been in Windows since at least
Win2000.

[Some peer post says that killing explorer.exe fixes it. I'll try that next
time]

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contextfree
I have no idea (don't personally remember encountering this), but the taskbar
has changed very little since Win7 (the only significant changes have been
improved multimonitor support and extending pre-existing features like jump
lists and badging to support modern apps), so it's not surprising if bugs
survived.

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NamTaf
I've seen it for years on my Win7 install but yet to see it on my Win10
install, which I got in mid-to-late June. But yes, it's always frustrated me
too and I don't know what's caused it.

I suspect it's one of those very low-priority bugs and thus never gets fixed.

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NathanKP
Interestingly the dock in Mac OS X has a similar bug. I have to do a `killall
Dock` from time to time to fix it.

My guess is there some kind of difficult to handle race condition around the
states on this type of system UI, particularly for laptops that go in and out
of suspend mode.

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nanny
As soon as I read your title I thought it might be this bug. I get it maybe a
few times per month in Windows 7. I have not seen it happen in Windows 10. You
can fix it without rebooting or killing explorer.exe by shift+right-clicking
on the taskbar item.

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UnoriginalGuy
I read your bug description through a few times, I am struggling to understand
what you mean. Are you saying the preview within the pop-up isn't updating
after a while or something else entirely? Or that the box doesn't auto-close?

~~~
Vendan
You know how when you hover over a taskbar button, it highlights and a little
preview pops up? When it _breaks_ , I get the highlight, and the popup, but
when my mouse moves away, they both stay there. Usually, I can move my mouse
back and out quick, and the preview popup goes away and stays gone, but the
highlight stays.

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dingo_bat
You can temporarily fix it by right-clicking any taskbar button while holding
shift. It works for me, until it's back again.

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elpocko
I've seen it in XP and 7, but not in 10.

