graceful suspend/resume support

[mixxxbot]

Reported by: ashley-boers
Date: 2018-01-22T05:11:32Z
Status: Confirmed
Importance: Medium
Launchpad Issue: lp1744641

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Mixxx 2.0.0 build 1.12r57772
Lenovo X220 Intel Core i5 2.5GHz 4GB
Windows 10 version 1709 OS Build 16299.192

With Auto DJ enabled Mixxx UI becomes unresponsive when laptop is closed.
Power management is set to only blank screen in this mode, and is configured for 'always-on' operation.
Mixxx outputs to SHOUTcast Server v2.5.5.733/win64, server does not log disconnect errors while Mixxx UI is unresponsive.

I could previously close lid and Auto DJ would operate in my absence.

Behaviour began (at best guess) following December 2017 Feature update to Windows 10, version 1709.

[mixxxbot]

Commented by: rryan
Date: 2018-09-21T01:49:06Z

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I've had issues with this before. We should verify all 3 platforms can suspend/resume gracefully, ideally handling reconnecting to audio interfaces, controllers, broadcasting, etc.