SwiftUI very likely is the future of app development. But it cannot, on its own replace UIKit or AppKit. Not yet, maybe not next year, either. Eventually you will have to drop down a level to implement a custom view, custom navigation, animation, window, or what have you. So for the time being, the two worlds of UIKit and SwiftUI co-exist and complement each other.
In short: Image file drag and drop does only produce file URLs, either with security scope-able bookmarks or plain file paths. Dragging an image file from Finder onto an NSTextView will trigger performDragOperation(_:). You get access to NSDraggingInfo there and can inspect available content. Its draggingPasteboard (shortened to pb here) contains the following data when executed on macOS 12 Monterey:
An old code base was still using Sparkler v1.27.0. To test the transition to the latest 2.x branch, the one that allows Sandboxing and uses XPC services under the hood, I migrated that project. Carthage builds of Sparkle’s v2.x branch don’t work well, though. You would need to do a lot of manual re-signing, otherwise the code signing stage of your build will fails. It does with a simple test project that embeds and signs the framework.
The Apple’s Human Interface Guidelines have a list of named system colors for macOS. These color names can be used for Emacs “faces”, i.e. color-and-font settings of text. Recently, this came in handy when Protesilaos Stavrou published his LIN package source code – it’s basically an extension of the built-in hl-mode, read: highlight-line-mode. The default highlights the current line. That’s kind of useful to find your insertion point more quickly. But it’s also used in selection interfaces to highlight the currently selected line: email modes like message-mode, notmuch, mu4e, and feed reader elfeed use this to show that the actions you can perform pertains to the currently focused or highlighted line. That’s where Prot’s LIN package comes into play: it helps distinguish between highlighting the line in text editing modes and highlighting the line in selection interfaces, so you can use different colors.