Mono Winforms on OS X

Despite some issues, my experience porting .NET C#/Winforms 2.0 code to a Linux system running Mono was surprisingly pleasant. Unfortunately, the same cannot be said for porting to OS X. Put simply, Mono Winforms on OS X sucks… it sucks bad… to the point where I question why it was even released.

fragmentsync mono winforms issues

The biggest and most apparent issues seems to be visibility and z-order issue. The image above is a form containing a few panels, however, only the panel containing the green header and the “sync with” label should the displayed. The others should be invisible (Control.Visible = false). Furthermore, making one control visible and another invisible or bringing a control to the front (Control.BringToFront()) such that it obscures others is a crapshoot; sometimes it’ll work correctly, other times you’ll see the correct control briefly before it disappears and your staring at a control that should be invisible or obscured.

Performance is atrocious. Winforms itself, even under .NET on Windows, is not a terribly high-performance windowing system, but it’s unbearable under OS X, to the point where you can see very prominent visual delays as events are processed and/or controls are being rendered.

Stability is awful. It’s not uncommon to reach a point where the application’s UI simply freezes up and no longer responds to events. Worse yet, disposal of Controls don’t seem to occur properly. I’ve noticed this on dynamically created controls, on a few occasions; clicking a control resulted in a crash because the control had already been disposed, but the control was still, incorrectly, being rendered in the UI and responding to events (hence the crash).

All of these problems seem to point to an issue with Mono’s per-windowing system driver for OS X. The Mono Project Roadmap indicates an upcoming Winforms update for OS X this September with the Mono 2.6 release, hopefully, it’ll address these (and I’m sure other) critical issues, so that Winforms can become truly cross-platform. As of right now, if your looking to use Mono Winforms as a solution for porting to OS X, you’ll likely only be able to pull off a port of the simplest of applications.

On a side note, Cocoa# looks like a pretty interesting project, but the website hasn’t been updated in months, so it’s possible the project is dead.