Update ui.Go() documentation to show that it will return nil when its main() returns now that that behavior is fully implemented.

init.go

@@ -3,7 +3,9 @@ package ui
 
 // Go sets up the UI environment and runs main in a goroutine.
 // If initialization fails, Go returns an error and main is not called.
-// Otherwise, Go does not return to its caller until (unless? TODO) the application loop exits, at which point it returns nil.
+// Otherwise, Go does not return to its caller until main does, at which point it returns nil.
+// After it returns, you cannot call future ui functions/methods meaningfully.
+// (TODO ideally we would want to be able to call ui.MsgBoxError() to report failures to the user, but I would need to figure out how to do this on platforms other than Windows.)
 //
 // This model is undesirable, but Cocoa limitations require it.
 func Go(main func()) error {

todo.md

@@ -25,7 +25,6 @@ so I don't forget:
 	- should message box text be selectable on all platforms or only on those that make it the default?
 
 important things:
-- ui.Go() should exit when the main() you pass in exits
 - because the main event loop is not called if initialization fails, it is presently impossible for MsgBoxError() to work if UI initialization fails; this basically means we cannot allow initializiation to fail on Mac OS X if we want to be able to report UI init failures to the user with one
 - figure out where to auto-place windows in Cocoa (also window coordinates are still not flipped properly so (0,0) on screen is the bottom-left)
 	- also provide a method to center windoes; Cocoa provides one for us but