Mark controls for widgets not rendered on URL currently previewed

[westonruter]

Currently the sidebar sections in the customizer will show/hide based on which sidebars are used on a given page (see #2). You can click around inside of the customizer to navigate to a page, and if that page template uses different sidebars, you'll see the sections in the customizer change while navigating.

It doesn't, however, hide widgets from the sidebar sections if they aren't currently rendered in the sidebar (e.g. via Widget Context or Jetpack's Widget Visibility). Perhaps the widget controls could be made opaque or minimized, for example:

See also: http://make.wordpress.org/core/2013/12/16/better-widgets/#comment-12125

[westonruter]

@MichaelArestad will mock up adding "This widget is not on the current page." to the inactive widgets.

[westonruter]

@MichaelArestad I'm going to close this issue. Any further improvements to the UI can be presented by you via a separate pull request.

[westonruter]

The logic for detecting whether a widget is rendered or not is not quite right it seems. The unpopulated RSS widget doesn't render anything, so it would seem like it should by default be semi-transparent. But when you first load the Customizer, it is fully opaque. If you try updating the widget or move it to another sidebar, it then becomes semi-transparent as expected.