SwitchResX enabling and disabling monitors confuses wallpaper generation

[Kevin Marino]

I use a 2018 Mac Mini with a Dummy HDMI plug and 2 monitors hooked to eGPU via DisplayPort.

Because of known behavior with waking the Dummy HDMI is needed on Mini itself. Also I use Hammerspoon to watch for wake for sleep and to cycle through SwitchResX profiles. 4K Monitors Dell U2718Q with HDMI,  DP, mini-DP ports both manually set to active port (auto gets confused when switching source computer)

I use 3 profiles:

- All monitors enabled (obviously the HDMI is not viewable)

- Dual Monitor (just the DisplayPort/eGPU) with Dummy HDMI Disabled

- Single Monitor (Just one DP monitor and the other two disabled)

The reason for this setup is that I have a work computer attached to one monitor and so during work hours often have the Mac in Single Monitor mode.

The problem may not be Multi-Monitor issue but SwitchResX, but figure post just in case.

Also if I have Dual Monitor and the wallpaper displaying across both correctly, then switch one monitor to say HDMI , Multi Monitor works and just displays the wallpaper on the single monitor at the correct scaling .

But if Hammerspoon runs and uses SwitchResX it gets confused and either I end up with both images sharing the single screen, or if already in single monitor mode the wallpaper is scaled incorrectly.  

To resolve I manually set both monitors to active and set Dual Monitor in SwitchResX, then I open multi-monitor and reload mmw file and apply.  Sometimes takes a couple of tries.

Lastly wallpaper cache clearing has no affect (this is why I wonder if it is a SwitchResX issue - I am reaching out to them also)

My last thought would be to use hammerspoon on the wake to do something with multi-monitor, but not sure from applescript what commands I could issue.

[Confused Vorlon]

I'm afraid this is too complicated for me to be really clear what is going on. I can throw in a couple of things though:

1) MacOS is pretty poor at handling desktop setting/scaling. If you're manually applying a wallpaper and it is scaled incorrectly - then there is a bug at the OS level.

resetting the wallpaper DB fixes most of these issues - but perhaps not all.

2) I think there _is_ an issue where MMW loses the specific layout for some monitor setup when you switch to a different set of monitors and then switch back. It reverts to the 'centre the image in the whole selection' mode.
I'll be investigating this shortly.

[Kevin Marino]

I think the 2) point is what is happening.   Yeah I haven't fully gone about documenting steps as as there are many variations.