[Affected versions]:

• Firefox 64.0
• Firefox 65.0b9
• Latest Nightly 66.0a1

[Affected platforms]:

• Windows 7 64bit
• Windows 10 64bit
• Mac OS X 10.11
• Ubuntu 16.04 32bit

[Steps to reproduce]:

1. Start firefox
2. Enable bookmark toolbar
3. Have 3-4 bookmarks in the bookmark toolbar
4. Drag the second bookmark to the right slowly

[Expected result]:

• The indicator showing where the bookmark will be moved is positioned one bookmark at a time.

[Actual result]:

• The indicator showing where the bookmark will be moved moves at the far right for a few pixel movement.

[Regression range]:

• This is an old regression. Mozregression pointed to the following pushlog:
  Last good revision: 564e82f0f289af976da01c2d50507017bbc152b5 (2017-08-15)
  First bad revision: 6ebc251bd288c268b020815025b05854ccde5c08 (2017-08-16)
  Pushlog:
  https://hg.mozilla.org/mozilla-central/pushloghtml?fromchange=564e82f0f289af976da01c2d50507017bbc152b5&tochange=6ebc251bd288c268b020815025b05854ccde5c08

Mike, could this be the result of fixing bug 1377968?

[Additional notes]:

• Gif showing the issue attached.

What happens is that there is some margin between buttons, so when you drag over that empty space, the system thinks you are dragging over the toolbar, and tries to append.

We should either take into account that space, or remove it by using padding instead of a margin.

It's very unlikely that my patch introduced this behavior, since I didn't touch spacing-related attributes there (margin, padding, or otherwise.)

I can't recreate this anymore. Can test verify?

I can reproduce on Win11, there's a small gap between bookmarks and if you drag on that gap the bug happens.

I can reproduce on Win11, there's a small gap between bookmarks and if you drag on that gap the bug happens.

Interesting. I see it disappear, but I don't see it move to the end like it used to.

Are your bookmarks overflowing into a menu? The move to the end in practice is "append at the end" and your end may be inside the overflow menu (So you won't see an indicator in the toolbar... one may argue we should highlight the menu in this case...).

Yes, thanks that was it.