[wp-trac] [WordPress Trac] #49288: Metabox holders missing their border and "Drag boxes here" text

[WordPress Trac]

#49288: Metabox holders missing their border and "Drag boxes here" text
-------------------------------------+-------------------------------------
 Reporter:  xkon                     |       Owner:  audrasjb
     Type:  defect (bug)             |      Status:  reviewing
 Priority:  normal                   |   Milestone:  5.5
Component:  Administration           |     Version:
 Severity:  normal                   |  Resolution:
 Keywords:  has-patch has-           |     Focuses:  ui, accessibility,
  screenshots                        |  administration
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Changes (by afercia):

 * keywords:  has-patch has-screenshots needs-refresh => has-patch has-
     screenshots


Comment:

 [attachment:"49288.3.diff"] builds on the previous patch and seeks to
 introduce a few improvements.

 To recap, the main purpose of this ticket is:
 - on the Dashboard: display the "Drag boxes here" text also on large
 screens
 - on the edit post pages: give the ability to move the post boxes to all
 the available areas, including the "advanced-sortables" one which isn't
 possible since [18975]

 Some testing would be nice. Please test at various resolutions and with
 the 2 column or 1 column layout, where applicable:
 - dashboard
 - edit post/page pages
 - edit attachment page

 **Details, TL;DR**

 - adds a `is-dragging-metaboxes` class to the body when dragging
 - simplifies the JS and adds the `is-dragging-metaboxes` CSS class to
 ''all'' the sortables in the Dashboard and in the various edit posts pages
 - displays the CSS generated content "Drag boxes here" only on the
 Dashboard
 - since this text is meant to appear only on the Dashboard, moves the
 related CSS to `dashboard.css`
 - makes sure the text is displayed also on large screens with a viewport
 larger than 1800 pixels
 - better scopes the CSS differentiating between the one for `#dashboard-
 widgets` and the one for `#post-body`
 - removes the CSS rulesets related to `.inner-sidebar` and `.has-right-
 sidebar` as they're no longer used since WordPress 3.4, see [20272] /
 #20015

 Visual changes for the Dashboard:
 - when dragging, the "empty" drop areas get a darker border
 - note: the empty areas are the ones that are really empty or that contain
 only hidden boxes

 Visual changes for the edit post pages:
 - when dragging, adds a visual indication of all the drop areas, making it
 possible to move post boxes also to the "advanced-sortables" area
 - to respect the original implementation intent, there's no change in the
 1 column layout

 Some relevant history related to columns and sortables:
 [18975] / #18314 / [20272] / #20015

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Ticket URL: <https://core.trac.wordpress.org/ticket/49288#comment:18>
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