Wikimedia Bugzilla is closed!

Created attachment 14335 [details]
Screenshot of the bug

See attached screenshot.

This is because the standalone demo initializes the target into a detached DOM element, then attaches it once it's done. But you can't do that, because it causes ve.ui.Toolbar.prototype.initialize to be run before the toolbar is attached to the DOM (and generally causes initialize to be run on unattached things, which is not allowed), which means its measurements will be wrong, and so the toolbar gets right: 1840px; (width of screen) rather than width: 63px; or whatever.