Headless (virtual) output renders as black screen in 0.52.2

[rothn]

Headless (virtual) displays in Hyprland appear to not render correctly in Hyprland 0.52.2 on Arch Linux kernel 6.18.2. I was trying to play a videogame on a multi-monitor WFH setup, and found I was not able to in Hyprland!

I added this to my config, to configure the monitor Hyprland would create:

monitor = HEADLESS-2, 7680x2160@60, 10000x0, 1

Then, I ran this to create the new virtual monitor and render a subset of its contents onto each of the two monitors:

hyprctl output create headless
wl-mirror -r "10000,0 3840x2160" -F --fullscreen-output DVI-I-1 HEADLESS-2 &
wl-mirror -r "13840,0 3840x2160" -F --fullscreen-output DVI-I-2 HEADLESS-2 &

Instead of seeing a desktop, as I expected, both monitors are just black. To be clear-- no waybar, no Hyprland background, just black.

hyprctl monitors shows this:

Monitor HEADLESS-2 (ID 3):
	[email protected] at 10000x0
	description: 
	make: 
	model: 
	physical size (mm): 0x0
	serial: 
	active workspace: 5 (5)
	special workspace: 0 ()
	reserved: 0 0 0 0
	scale: 1.00
	transform: 0
	focused: no
	dpmsStatus: 1
	vrr: false
	solitary: 0
	solitaryBlockedBy: windowed mode,missing candidate
	activelyTearing: false
	tearingBlockedBy: next frame is not torn,user settings,not supported by monitor,missing candidate
	directScanoutTo: 0
	directScanoutBlockedBy: user settings,missing candidate
	disabled: false
	currentFormat: XRGB8888
	mirrorOf: none
	availableModes: [email protected] 
	colorManagementPreset: srgb
	sdrBrightness: 1.00
	sdrSaturation: 1.00
	sdrMinLuminance: 0.20
	sdrMaxLuminance: 80

This seems like a bug to me, particularly in light of the discussion of a similar issue at #5415 , which was closed as stale because of the "Hyprland bug reports should be discussions" policy. I was not able to find a follow-up, so I am creating this.