qml: animate playqueue x position when hiding instead of its width

changed milestone to %4.0

added Component::Interface: Qt label

added MRStatus::Reviewable label

To be honest, this animation could be both x animation and width animation. With the play queue, we don't have growing controls side-effect as in the mini player. So I did not see the necessity of applying the same change here.

As a user, I would personally prefer width animation here. I see it as a growing pattern when I enable the play queue.

As a user, I would personally prefer width animation here. I see it as a growing pattern when I enable the play queue.

I feel the opposite way, having elements collapsing one into the other feels odd

One advantage is that the length appears earlier with width animation. For the collapsing, they should instead elide, but I guess they are not configured like that.

Width animation is also more in-line with user resizing, in which the width is controlled.

User resizing can't be anything else than width controlled.

I believe that "x" animation is a more widespread pattern, the first example I've been able to find uses this (youtube, slack, gitlab, qt documentation). But I'm sure there are counter examples. In the end, that's a design decision, both point of view are acceptable, so I'm ok to hold this until other people weight in.

I'm also okay if this is accepted, I just wanted to mark this as a point. Besides, x animation should perform better.

added MRStatus::InReview label and removed MRStatus::Reviewable label

added MRStatus::NotCompliant label and removed MRStatus::InReview label