A more efficient customizer (width)

[scottwyden]

I have been thinking long and hard about the customizer and its efficiency. Since the use of the customizer is becoming a standard for themes, I think more focus needs to be put on the UI of it.

My first thought is related to the 300px size it sits in. That's very narrow for an efficient workflow. I think it could be doubled, easily.

But how to double it is the key. In my opinion, making the customizer 600px when a mouse is hovered on top of the customizer window is a smart move.

That way there is enough spacing to really see the theme options without being confined to a 300px narrow strip.

But when a mouse is moved off of the customizer, like when scrolling to see the live demo, then it can collapse down to 300px so it takes up less space.

On mobile it can also stay confined to 300px, or 50% of the screen if on an iPad in landscape.

Here is a screenshot of how 600px would look on a 15" screen: ​http://take.ms/s7OHU

[ocean90]

Duplicate of #32296.