Assertion failure in headless backend

[any1]

The following assertion fails when mpv is put into fullscreen mode on a headless output:

sway: backend/headless/output.c:94: output_commit: Assertion `output->back_buffer != NULL' failed.

Backtrace:

#0  0x00007fed0dea4615 in raise () from /usr/lib/libc.so.6
[Current thread is 1 (Thread 0x7fed0d258940 (LWP 121952))]
(gdb) where
#0  0x00007fed0dea4615 in raise () at /usr/lib/libc.so.6
#1  0x00007fed0de8d862 in abort () at /usr/lib/libc.so.6
#2  0x00007fed0de8d747 in _nl_load_domain.cold () at /usr/lib/libc.so.6
#3  0x00007fed0de9cbf6 in  () at /usr/lib/libc.so.6
#4  0x00007fed0e73b0d6 in output_commit (wlr_output=0x557be1744a30)
    at ../subprojects/wlroots/backend/headless/output.c:94
#5  0x00007fed0e778ed6 in wlr_output_commit (output=0x557be1744a30)
    at ../subprojects/wlroots/types/wlr_output.c:598
#6  0x0000557be0bbc48a in scan_out_fullscreen_view
    (output=0x557be18970f0, view=0x557be1bfe540) at ../sway/desktop/output.c:555
#7  0x0000557be0bbc564 in output_repaint_timer_handler (data=0x557be18970f0)
    at ../sway/desktop/output.c:580
#8  0x0000557be0bbc846 in damage_handle_frame
    (listener=0x557be1897270, user_data=0x557be18972c0) at ../sway/desktop/output.c:671
#9  0x00007fed0e78b9a3 in wlr_signal_emit_safe (signal=0x557be1897320, data=0x557be18972c0)
    at ../subprojects/wlroots/util/signal.c:29
#10 0x00007fed0e772bd8 in output_handle_frame (listener=0x557be18973d0, data=0x557be1744a30)
    at ../subprojects/wlroots/types/wlr_output_damage.c:56
#11 0x00007fed0e78b9a3 in wlr_signal_emit_safe (signal=0x557be1744bb8, data=0x557be1744a30)
    at ../subprojects/wlroots/util/signal.c:29
#12 0x00007fed0e779269 in wlr_output_send_frame (output=0x557be1744a30)
    at ../subprojects/wlroots/types/wlr_output.c:678
#13 0x00007fed0e73b395 in signal_frame (data=0x557be1744a30)
    at ../subprojects/wlroots/backend/headless/output.c:166
#14 0x00007fed0e0bb1dd in wl_event_loop_dispatch () at /usr/lib/libwayland-server.so.0
#15 0x00007fed0e0b94e7 in wl_display_run () at /usr/lib/libwayland-server.so.0
#16 0x0000557be0bb7a4e in server_run (server=0x557be0c2f320 <server>) at ../sway/server.c:244
#17 0x0000557be0bb6f4a in main (argc=1, argv=0x7ffcfaa676e8) at ../sway/main.c:412

Steps to reproduce:

• Run WLR_BACKENDS=headless sway (built from master branch)
• Run WAYLAND_DISPLAY=wayland-1 wayvnc
• Connect to the VNC server using some client, e.g. wlvncc
• Play a video in mpv and put it into fullscreen mode

[emersion]

Can you try #2524?

[any1]

Yeah, that fixes it.

An unrelated "problem" is that I always get this printed out to the terminal when in full screen. But it was like that before:

[types/wlr_output.c:579] Basic output test failed

I also get this printout whenever there's something new rendered, which (IIRC) only started happening after the v6 update.

[EGL] command: eglGetConfigAttrib, error: EGL_BAD_CONFIG (0x3005), message: "eglGetConfigAttrib"

[emersion]

Basic output test failed

Hm, I don't get that on AMD. I'm running mpv --hwdec=none --fullscreen whatever. What hw and test client are you using?

eglGetConfigAttrib, error: EGL_BAD_CONFIG (0x3005), message: "eglGetConfigAttrib"

Yeah, wlroots tries to figure out whether there is an alpha channel by reading the EGL config. This is incorrect when a FBO is used, and since #2510 we don't have a config anymore. Opened #2527 to track it, in the meantime it's mostly harmless and it'll just mean you'll get RGBX via screencopy shm instead of RGBA.