Hi,
since some months I'm working on a cross-platform project; cross-platform means, I would like to get it run on win64 and macOS 64bit. My development platform is macos 10.10 with Lazarus 1.6.4. I started with the carbon widgetset (IDE always carbon), made some experiences with colors, fontsizes and not really working border settings. But ok, the application works fine and can be compiled under WinXP and Win10 without errors. There are some minor adjustments necessary concerning fonts and font sizes and relative adjustments of GUI components, but the result is good enough. The functionality including SQLite database is without any problem.
But what will happen in the future? Within the next one or two years all 32bit applications won't no longer work on actual macOSses. So it seems to me the only way of survival on macOS is migrating to Cocoa 64bit widgetset. So I made my first experiences with Cocoa. IDE stayed on carbon, compiler switch was set to cocoa. Some minor bugs could be handled by workarounds, but then came some severe problems (app crashes on opening a windows OnShow Event, another window only showed less than the half of all visual components, ...). I doubt, that cocoa will ever be a stable platform on macOS. That would mean (for me), that Lazarus will die for macOS within the next two years.
My first Pascal course was in 1981 (may be, I'm an IT grandfather), then stepped into UCDS Pascal with Apple II, followed by Delphi about 20 years ago. I'm loving this language very much and would do much to help further development for this platform. I'm not a real IT compiler technician and I cannot look very deeply into the secrets of the underlying libraries, but I decided to register for the freepascal bug tracker and to help a little bit to make lazarus-cocoa as a stable pascal software development platform.