Should contextual balloon be displayed when target is out of the viewport?

[Reinmar]

This looks bad. Especially, when scrolling the content. I'm not sure what we could do.

• Should the toolbar be above the balloon?
• Should we hide the balloon?
• Should the balloon stick to the top and move no further?

[oskarwrobel]

Very similar: https://github.com/ckeditor/ckeditor5-ui/issues/181

[oleq]

Should the toolbar be above the balloon?

Just like the dialog floats over the entire web page, the balloon should be on top because it is the actual context of the user at that particular moment. We should rather hide the balloon when they overlap.

Should we hide the balloon?

Yes. As soon as the bottom edge of the target goes off-screen.

Should the balloon stick to the top and move no further?

No, because then the balloon remains in the context of something supposedly far, far away and long forgotten by the user, thus becoming an orphan UI.

[Reinmar]

I'm adding it to milestone 11 to discuss this ticket's priority, but AFAIR it was blocked by the async UI API refactoring.