On Mon, 06 Sep 2021 13:50:52 +0300 Eli Zaretskii wrote: >> Date: Mon, 06 Sep 2021 16:12:56 +0800 >> From: Po Lu via "Bug reports for GNU Emacs, >> the Swiss army knife of text editors" >> >> >> Enable tab-bar-mode, move the mouse pointer over the "+" button used to >> create new tabs. Once the button is highlighted by displaying a relief, >> move the pointer back outside the tab bar. >> >> While most the relief around part of the button will be cleared, part of >> the left side of the relief that surrounded the "+" button when it was >> highlighted will be retained. >> >> To the best of my knowledge, this also appears on Emacs 28. > > FWIW, I cannot reproduce this, neither in Emacs 27.2 nor in Emacs 28. > > Maybe this is window-system dependent? > > Alternatively, if you have some "optimization" features enabled in > your video drivers, disable them and try again. I see the problem with Emacs 27 and 28 built with Gtk+ and with 28 built with no toolkit (I don't have a built of 27 with no toolkit). It looks like a remnant pixel on the lower left, see attached screenshot. It disappears as soon as the window size changes. Steve Berman