One of macOS Catalina's biggest new features for developers is Mac Catalyst—initially known as Project Catalyst—which Apple says makes porting iPad apps to the Mac as easy as checking a box in Xcode.
However, more work is required for the iPad apps to truly resemble native Mac apps, and Bloomberg's Mark Gurman reports that some developers have encountered "several problems" with Catalyst so far.
For example, the report claims that James Thomson had to work harder than he expected to get his popular PCalc calculator app for iPad to run well on the Mac. Thomson said the Mac version initially "looked like an iPad app floating on a larger Mac screen," so he had to redesign much of the user interface.
Thomson added that some older Macs struggle to handle Catalyst-based apps that use Apple's high-level 3D graphics framework SceneKit.
Lukas Burgstaller, developer of the RSS reader Fiery Feeds for iPad, also "ran into all sorts of walls" trying to adapt the iPad app to the Mac interface using Catalyst, but the report does not mention any specific issues he faced.
On the consumer side of things, the report notes that Catalyst results in users paying twice for the same app across iOS and macOS.
"As a user, I don't want to pay again just to have the same app," well-known developer Steven Troughton-Smith told Bloomberg. "As a developer, I don't want my users to have to make that decision."
Troughton-Smith touched on some of the issues developers are facing with Catalyst, noting that Mac versions of some apps can't hide the mouse cursor while video is playing, or may have issues with video recording, two-finger scrolling, or using the keyboard and full-screen mode in video games.
The report adds that two upcoming Catalyst apps that had been featured on Apple's website since June were removed this week, including comic book app DC Universe and the racing game Asphalt 9. It is unclear if the Mac apps are no longer planned or delayed, or if any of the Catalyst issues reported were a factor.
Netflix also confirmed that it has no plans to develop a Mac app using Catalyst at this time, according to the report.
Despite all of this, Troughton-Smith believes Catalyst is the "future of Mac app development," and he is impressed with many of the first apps. There might just be a few growing pains along the way.
macOS Catalina was widely released on Monday.
Update: Gameloft says Asphalt 9 for Mac via Catalyst has been "slightly delayed" in order to "polish the experience" and that it will launch later this year, according to a follow-up tweet from Gurman.
