Monitor hotplugging issues

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I have two displays, one 2K monitor that's connected via HDMI and one 4K monitor via DP.

• Disconnecting the second (DP) monitor works fine. Only when I reconnect it, the swaybar always becomes inverted (the right bar shows the left screen's workspaces and vice versa) and the new monitor's background/wallpaper is black. The bar disappears (crashes?) whenever I try to scroll through it (with mousewheel) once it's inverted. Else it just remains this way forever even through subsequent hotplugging (showing no workspaces at all when there's just a single display connected).
• Launching sway on the first (HDMI) monitor and only then connecting the other one works fine - no issue with the bars or the wallpaper.
• In both cases (so whenever I have hotplugged my 4K monitor instead of it being still there from startup), many applications (emacs, mumble, etc) start rendering text (and only the text) in a bigger font size. Interestingly, this would be exactly what I want (on this monitor at least) but it appears to be distinct from sway's actual highdpi support (I disabled that because I don't like the blurriness you get from scaling).

(Originally reported at swaywm/sway#960 (comment))