Created attachment 8651530 [details] Popup menus from toolbar have wrong placement of triangle if window size is narrow enough.png STR: (Win7, Nightly 43.0a1 (2015-08-20)) 1. Place Pocket button and History button on toolbar. 2. Doch the window to the left side of screen, place mouse over right border of the window and drag it to the left to make window's width as small as possible (to cause overflow) 3. Click #nav-bar-overflow-button to view hidden buttons in toolbar 4. Click Pocket/History button Result: Triangle is placed at the right top of menu popup Expectations: Triangle should be placed at the left top of menu popup Note: I can reproduce it with Pocket and History buttons. However, it may and WILL happen with add-ons that provide wide popups, and user may set HiDPI on his mashine. In these cases you don't even need to make the window too narrow to reproduce it.