Window X/Y offsets (specified through --geometry) ignored on Wayland

Important Information

mpv version:

mpv 0.33.0-dirty Copyright © 2000-2020 mpv/MPlayer/mplayer2 projects
 built on UNKNOWN
FFmpeg library versions:
   libavutil       56.51.100
   libavcodec      58.91.100
   libavformat     58.45.100
   libswscale      5.7.100
   libavfilter     7.85.100
   libswresample   3.7.100
FFmpeg version: n4.3.2

Linux Distribution and Version: archlinux (updated ~week ago), output of uname -a follows

Linux davos 5.11.10-arch1-1 #1 SMP PREEMPT Fri, 26 Mar 2021 00:11:29 +0000 x86_64 GNU/Linux

Source of the mpv binary: official distribution package

If known which version of mpv introduced the problem: unknown, issue discovered when transitioning from X11 to Wayland

Window Manager and version: sway 1.5.1, installed from official distribution package

GPU driver and version: nothing fancy, using Intel graphics, so i915 + MESA, details follow

$ lspci -vnn | grep VGA -A 12
00:02.0 VGA compatible controller [0300]: Intel Corporation UHD Graphics 620 (Whiskey Lake) [8086:3ea0] (rev 02) (prog-if 00 [VGA controller])
	Subsystem: Lenovo Device [17aa:2279]
	Flags: bus master, fast devsel, latency 0, IRQ 138, IOMMU group 1
	Memory at d7000000 (64-bit, non-prefetchable) [size=16M]
	Memory at b0000000 (64-bit, prefetchable) [size=256M]
	I/O ports at 3000 [size=64]
	Expansion ROM at 000c0000 [virtual] [disabled] [size=128K]
	Capabilities: <access denied>
	Kernel driver in use: i915
	Kernel modules: i915

$ glxinfo | grep OpenGL
OpenGL vendor string: Intel
OpenGL renderer string: Mesa Intel(R) UHD Graphics 620 (WHL GT2)
OpenGL core profile version string: 4.6 (Core Profile) Mesa 21.0.1
OpenGL core profile shading language version string: 4.60
OpenGL core profile context flags: (none)
OpenGL core profile profile mask: core profile
OpenGL core profile extensions:
OpenGL version string: 4.6 (Compatibility Profile) Mesa 21.0.1
OpenGL shading language version string: 4.60
OpenGL context flags: (none)
OpenGL profile mask: compatibility profile
OpenGL extensions:
OpenGL ES profile version string: OpenGL ES 3.2 Mesa 21.0.1
OpenGL ES profile shading language version string: OpenGL ES GLSL ES 3.20
OpenGL ES profile extensions:

Possible screenshot or video of visual glitches: no glitches per se, but I still took a screenshot

Reproduction steps

Run the following command:

mpv \
    --no-config \
    -v -v \
    --log-file=mpv-bug.log \
    --geometry=50:40 \
    --image-display-duration=inf \
    /usr/share/backgrounds/sway/Sway_Wallpaper_Blue_1136x640.png

Expected behavior

The window of mpv should be placed at x=50, y=40.

Actual behavior

The window of mpv is aligned to the center of the display.

Log file

Attached as mpv-bug.log

NOTE: even though the log was produced with a multi-display setup, I verified earlier that the number of displays does not affect the issue in any way.

Sample files

N/A

Reproduce the issue under sway with the exact --geometry=50:40 command and inspect the attached mpv-bug.log alongside the verbose output. Trace the Wayland window-placement entry point and verify that the mpv window honors the requested x=50, y=40 offsets rather than being centered.