Taskbar buttons don't appear when coming back from sleep/hibernation

[SMUsamaShah]

#439 added ability to show buttons on their own displays.

Sometimes, taskbar buttons don't appear on a display or don't appear for some windows.

I have two extra displays attached. Steps to reproduce are usually like:

• Windows open on all displays
• Hibernate
• Turn on the computer, login.
• (Since extra displays are connected via docking station, there is sometimes a lag and those displays don't turn on immediately. This also causes windows to swap between displays or move to other display.)
• (No shuffling/moving of windows happen, all windows are in the same place as I left while hibernating.)
• But now one of the Taskbars is not showing buttons for any of the windows on that screen.
• Workaround: Untick "Show on multiple displays", then tick again to refresh the buttons.

[plovlover]

I can confirm that this bug still persists on 1.13.30

[dremin]

This build should fix the issue if you'd like to try it early.