Media: Attachment Display Settings inside Galleries don't work

[designsimply]

Steps to reproduce:

1. Create a new post
2. Click the "Add Media" button
3. Upload or select a few files
4. Click "Create Gallery" on the left
5. Click the "Create a new gallery" button at the bottom right
6. While on the "Edit Gallery" screen, click on one of the images, and scroll down on the right until you see the "Attachment Display Settings" section
7. Select "Link To" = "Custom URL" under "Attachment Display Settings" at the bottom right
8. Enter a URL and click the "Insert gallery" button
9. Click the "Edit" icon on the gallery to go back to the "Edit Gallery button screen again
10. Click the the image you just added a Custom URL to
11. Look to see if the Custom URL is still present
12. Try setting the link to none and checking it again, it doesn't save that option either. In fact, alignment saves, but he link and size settings don't. I'm not sure the Attachment Display Settings" options should even be present in that screen though.

• Expected: Attachment Display Settings like "Link To" on the Edit Gallery screen to save and work on images inside galleries as expected
• Actual: Attachment Display Settings on the Edit Gallery screen don't work

Tested with core trunk r28663 and on WordPress.com.

Reported by a WordPress.com user who was unable to get Custom URLs to work—I think we are semi?-merged up to r28625.

[designsimply]

511559 (ignore this)

[SergeyBiryukov]

Related: #13429

[wonderboymusic]

Let's take a look

[Ipstenu]

This is a regression from 3.9 where that field is hidden when you're in the gallery.

If you do want it (and frankly, I do) there's a plugin: ​https://wordpress.org/plugins/wp-gallery-custom-links/

Suggest it get removed from the 4.0 editor for galleries :) Unless we're using it for real and then I love you.

[wonderboymusic]

In 29285:

Don't render Attachment Display Settings when display is set to false. Currently, the value for display in the media.view.AttachmentsBrowser instance in the media.view.MediaFrame.Select frame is set to the value for displaySettings.
These values do different things, so check for the existence of display on the state before arbitrarily setting it to the displaySettings value.

Real world: this hides display settings when you select an image while editing a Gallery.

Fixes #28653.