Modernize Media screen

[kean]

Spec: UI Modernisation: Media on iOS.

Foundation ✅

The existing Media screen implementation relies heavily on MediaPicker framework, which is written in Objective-C and hasn't received a lot of attention recently. The framework attempts to generalize the code that displays images from different sources: your WordPress media library, Photos, Free Photos and GIFs, and more, which makes it brittle and hard to modify. The existing implementation also has some severe performance issues with thumbnail loading and caching, which have to be addressed.

In version 23.2, we've made the first step on the road to replacing the MediaPicker framework: integrating PHPickerViewController. The next step is to reimplement the Media screen in Swift while fixing the many unaddressed performance and other issues. This ticket covers it.

The first part of this ticket covers reimplementing the core Media screen functionality in Swift.

• Media: Add new screen #21470
• Media: Implement sync of assets #21542
• Media: Implement media uploads #21562
• Media: Implement empty state view #21566
• Media: Implement edit mode #21580
• Media: Implement search #21601
• Media: Thumbnails #21615
• Media: Implement picker mode #21651
• Media: Add support for remaining asset types #21664
• Media: Add support for self-hosted sites #21673
• Media: Add progress reporting #21678

Modernization ✅

The second part of this ticket covers the new features and design improvements.

List

• Use new context menus for media picker (done in #21562)
• Add GIF playback support
• Media: Add support for selection with pan gesture #21702
• Site Media: Display storage quota when adding content #22013
• Site Media: Add aspect mode on iPad (Experimental) #22009

Details

• Allow swiping between photos and switch to adjacent items when deleting the selected one [Site Media: Improve media details screen #22008]
• Refresh the design [Site Media: Improve media details screen #22008]
• Use optimistic UI for savings metadata changes [Site Media: Improve media details screen #22008]

Fixes

• Fix an issue with blank placeholders during image uploading (PR: #21470)
• Media Library: 'you have no media' appears just before the media does. #9922
• Fix an issue with images flashing on pull-to-refresh
• NSRangeException: *** -[__NSArrayM objectAtIndex:]: index 0 beyond bounds for empty array #21572
• Fix an issue with incorrect background color used for audio and document view until the cell is reused

Thumbnail Loading Improvements ✅

• Add prefetching (PR: #21470, fixes: #4288)
• Cancel the requests when cells moved offscreen (PR: #21470, fixes: #14528)
• Fix main thread performance issues due image decompression happening on the main thread (PR: #21470)
• Remove transcoding when downloading remote thumbnails and store original thumbnail data in local cache
• Use URLSession with no URLCache to avoid double-caching it: the service has its own disk cache
• Use absoluteThumbnailLocalURL for storing thumbnails. It gets populated by MediaImportService when the assets are added, so we avoid duplicating the work of generating the thumbnail
• Move disk I/O to background threads
• Removes unnecessary coreDataStack.mainContext.perform hops and use @MainActor to enforce thread confinement

[kean]

It's done.