Tile Windows mode: Connecting external display moves windows to external display

[brs17]

Distribution (run cat /etc/os-release):
Pop!_OS 20.04

Related Application and/or Package Version (run apt policy pop-shell or provide the latest commit if building locally):
pop-shell 0.1.0~1589481653~20.04~87a5f44

Issue/Bug Description:
With windows opened and tiled on a primary laptop display, an external display is then connected. The open windows move over to the external display.

Steps to reproduce (if you know):

1. Boot Pop!_OS 20.04
2. Enable "Tile Windows"
3. Launch one or more programs (gnome-terminal and firefox seem to work fine)
4. Plug in external display
5. See windows move to newly added display

Expected behavior:
Programs remain where they were before plugging in the external display.

Other Notes:
This behavior does not happen if the programs are not tiled.

[WatchMkr]

I thought we had this one but my test was bad. Adjusting the testing doc accordingly.

If I plug a second monitor into a laptop the windows move to the external display (and shouldn't). If adding a third monitor to a closed and disabled laptop display, the windows stay put.

[brs17]

I thought we had this one but my test was bad. Adjusting the testing doc accordingly.

If I plug a second monitor into a laptop the windows move to the external display (and shouldn't). If adding a third monitor to a closed and disabled laptop display, the windows stay put.

I don't think your test was "bad" persay. I think this highlights though that we may want to specify testing a number of different displays.

[toreanderson]

I find this issue quite annoying. I am normally docked to an external UHD monitor with the laptop lid down (i.e., the laptop's internal FHD display is off). However, I occasionally need to open my laptop lid, in particular when I need to use my webcam (which is physically embedded in the laptop lid itself).

The external monitor is configured as the primary monitor in the GNOME settings, so it has the top bar, the activities menu and the workspaces. The laptop display only has a single workspace due to /org/gnome/mutter/workspaces-only-on-primary being true.

While working I might have several windows neatly arranged across several workspaces, which I have illustrated here with eight coloured terminals evenly divided across two workspaces:

However, the moment I open my laptop lid, all eight terminals instantly migrate to the laptop monitor. Since that one does not have workspaces, they all get mixed up on the same screen, as shown below:

Opening the laptop lid also removed all the workspaces on the external screen, as can be shown in the activities view:

If I at this point close the laptop lid again, all the windows migrate back to the primary monitor, as expected. However, they do not get organised back in the different workspaces they started out with, they are still all mixed up on a single workspace:

As we can see in the activites view, that single workspace is the only one there is (disregarding the empty one GNOME always adds at the bottom):

At this point I have to clean up this mess, which is rather annoying and tedious.

I suggest that the behaviour is changed as follows:

1. Windows should not migrate to a newly connected secondary display. That is, if a new secondary display is connecting, simply leave all the windows exactly where they were before and make the newly connected secondary display empty.
2. If a new primary display is connected, then migrate all windows and all workspaces as they are currently arranged to the new display, leaving the workspace on the display newly demoted to secondary empty. This would cover the case when I have been working on my laptop and then dock it to the external monitor.
3. If the primary display is disconnected, then migrate all windows and all workspaces as they are currently arranged to the new primary. However, if there were open windows on the secondary display that got promoted to the primary, move them to the workspace that was active on the primary display and perform normal tiling (as if they were new windows being opened there). This covers the case when I disconnect my laptop from external monitor to go somewhere with it.
4. If the secondary display is disconnected, then migrate any windows that were open on the secondary display to the currently active workspace on the primary, re-tiling as appropriate. This covers the case where I close my laptop lid while docked to the external monitor.

3 and 4 presumes that workspaces-only-on-primary == true. If false, then simply merge the workspaces one by one and re-tile as appropriate.

[toreanderson]

Come to think of it, another possible and reasonable way of handling disconnecting displays (case 3 and 4 above) is to move the workspaces and their windows from the disconnected display into one or more new workspaces on the primary display. This would allow for keeping the tiling layout as-is (although the windows might need to be resized if the workspace resolution changes).

[mmstick]

Pop Shell was doing this, but something must have broken somewhere if it's not doing it anymore

[toreanderson]

I just found out that after having played around a bit with re-arranging the location of the secondary display in the GNOME monitor settings, the bug no longer occurs - even though I moved the secondary display back to its original location afterwards (which was to the left of my main display).