State of Apple's Catalyst

At its developer conference in June this year, Apple introduced Project Catalyst that aims to help developers swiftly bring their iOS apps to Macs. Developers have had more than half a year to play with Catalyst. Here's where things stand currently: The crux of the issue in my mind is that iOS and Mac OS are so fundamentally different that the whole notion of getting a cohesive experience through porting apps with minimal effort becomes absurd. The problem goes beyond touch vs pointer UX into how apps exist and interact within their wider OSes. While both Mac OS and iOS are easy to use, their ease stem from very different conventions. The more complicated Mac builds ease almost entirely through cohesion. Wherever possible, Mac applications are expected to share the same shortcuts, controls, windowing behavior, etc... so users can immediately find their bearings regardless of the application. This also means that several applications existing in the same space largely share the same visual and UX language. Having Finder, Safari, BBEdit and Transmit open on the same desktop looks and feels natural.

By comparison, the bulk of iOS's simplicity stems from a single app paradigm. Tap an icon on the home screen to enter an app that takes over the entire user experience until exited. Cohesion exists and is still important, but its surface area is much smaller because most iOS users only ever see and use a single app at a time. For better and worse, the single app paradigm allows for more diverse conventions within apps. Having different conventions for doing the same thing across multiple full screen apps is not an issue because users only have to ever deal with one of those conventions at a given time. That innocuous diversity becomes incongruous once those same apps have to live side-by-side.

Columnist John Gruber of DaringFireball adds: I think part of the problem is Catalyst itself -- it just doesn't feel like nearly a full-fledged framework for creating proper Mac apps yet. But I think another problem is the culture of doing a lot of nonstandard custom UI on iOS. As Wellborn points out, that flies on iOS -- we UI curmudgeons may not like it, but it flies -- because you're only ever using one app at a time on iOS. It cracks a bit with split-screen multitasking on iPadOS, but I've found that a lot of the iPad apps with the least-standard UIs don't even support split-screen multitasking on iPadOS, so the incongruities -- or incoherences, to borrow Wellborn's well-chosen word -- don't matter as much. But try moving these apps to the Mac and the nonstandard UIs stick out like a sore thumb, and whatever work the Catalyst frameworks do to support Mac conventions automatically doesn't kick in if the apps aren't even using the standard UIKit controls to start with. E.g. scrolling a view with Page Up, Page Down, Home, and End. Further reading: Apple's Merged iPad, Mac Apps Leave Developers Uneasy, Users Paying Twice (October 2019).

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