Drag'n'drop menu does not play nice with responsive layout

[AppSynergy]

Affects the Appearance > Menus admin page.

When the viewport is larger than 900px, drag'n'drop works splendidly.
Issue: none

When the viewport goes < 900px, the left hand admin navigation shrinks as expected, I don't see any other visible changes.
Issue: now when you try to drag'n'drop menu items vertically in the list, they tend to jump to the right and become sub-items. A fairly dramatic leftwards translation will override this.

When the viewport goes < 800px, the whole page layout switches from two columns to one.
Issue: now when you try to drag'n'drop menu items vertically in the list, the viewport scrolls down quite rapidly, and they become sub-items. No amount of leftwards translation will override this.
Holding the mouse button and trying to scroll up results in the viewport scrolling down again.

Suspect: drag'n'drop js doesn't know that it's possible for the layout the respond to the viewport size.

[helen]

Hi AppSynergy - thanks for the detailed report. I definitely see a bit of weirdness around responsive and nav menu editing - there's some horizontal scrolling around that 900px breakpoint, so I wonder if that's contributing to the strange behavior. However, I'm not reproducing what you've described exactly - could you let us know what browser and OS/device you're using? A screencast would also be really awesome, but not to worry if you can't.

[chriscct7]

No reporter feedback in 2 years. Closing as worksforme. Feel free to reopen if you can provide steps to reproduce