#3253 Immigrants list disappears after first viewing.

[James Kuyper]

The first time I go to the immigration section of the Difficulty screen, it shows a list of predetermined immigrants. That list disappears when I come back to that section, until I dismiss the Difficulty screen. The next time I open the Difficulty screen, the immigrants list shows up again.

[Calebrw]

Confirmed as of [bbf606].

I'm not 100% sure, but I think was introduced around the time @stiangre committed [89c6b1]. I took a look at SwingGUI.java method showClientOptionsDialog() and I see refreshGuiUsingClientOptions() is the only thing new since 2020.

[Stian Grenborgen]

This is caused by:

setLayout(null);

...in MigPanel.removeNotify.

I would normally fix this by just removing that statement, but it was added in a commit named: "MigLayout leakage fixes" in 2013.

In FreeColPanel, the following explanation is given:

    // We need to make sure the layout is cleared because some
    // versions of MigLayout are leaky.

@mpope: Is this cleanup code still needed? If yes, then we should add a "addNotify"-method as well. This is also true for all other uses of removeNotify -- like in FreeColPanel.

[Mike Pope]

Is this cleanup code still needed?

I do not know. 2013 is a long time ago, but there has been very little change to MigLayout AFAICT. It appears to be stuck at v5.0, which is what we have been distributing since 2017. I recommend we remove the offending line and keep an eye out for memory problems in the absence of a better plan.

[Stian Grenborgen]

Fixed. You can verify the fix using the development version:
https://github.com/FreeCol/freecol/releases/tag/latest