#517 File dialog based observation source UI freeze

[David Benn]

There is a non-deterministic UI freeze before file based observation source file choosers load.

I suspect I saw this in the previous release but was unable to reproduce it.

This has the smell of a deadlock. Need to look at what changed in the plugin handling code in the last two releases.

[David Benn]

This appears to happen before the ob source plugin file chooser dialog is finished being created or at least opened. Debug efforts should start there. If the dialog (a singleton as I recall) is opened successfully once, it seems to be okay for all file based obs source plugins thereafter.

Given the nature of deadlocks however, I may just be getting fooled.

[David Benn]

Okay, so it may be that we are breaking a Swing rule by calling the file dialog in Task.doInBackground().

See :
https://stackoverflow.com/questions/22949488/getting-a-deadlock-in-swing-unsure-how-to-proceed
https://stackoverflow.com/questions/3902148/jfilechooser-showopendialog-not-opening-and-no-error-being-thrown

[David Benn]

Looks like I'll need to move the file chooser code to a method that's called before the retriever code in the background thread.

[David Benn]

I have fixed this non-determinisitc bug by moving the file chooser into a configure() method that is called before the background thread is invoked to load observations. It's that part we want progress info for anyway.

[David Benn]

Tested all ob source plugins since they all use this common code.

[David Benn]

Fixed in 2.20.0