Property window-scale is incorrect after fullscreen #4323

mpv version and platform

OSX 10.11

cplayer: mpv git-1a0c340 (C) 2000-2017 mpv/MPlayer/mplayer2 projects
cplayer:  built on Sat Apr 15 21:05:27 CEST 2017
cplayer: ffmpeg library versions:
cplayer:    libavutil       55.58.100
cplayer:    libavcodec      57.89.100
cplayer:    libavformat     57.71.100
cplayer:    libswscale      4.6.100
cplayer:    libavfilter     6.82.100
cplayer:    libswresample   2.7.100
cplayer: ffmpeg version: 3.3

Reproduction steps

1. Query window-scale
2. Go to fullscreen
3. Query window-scale
4. Wait 2 seconds
5. Query window-scale

(See script below)

Expected behavior

window-scale from step 3 and 5 should match.

Actual behavior

window-scale in step 1 and 5 match.
Note that using mp.observe_property will only return correct window-scale values and not exhibit this problem.

Log file

Test made with this script: https://gist.github.com/Argon-/aadd9b337ca4d419b492d369ec99553b
After pressing i it will print window-scale, go to fullscreen and print window-scale again as well as start a timer that will print window-scale a third time after 2 seconds, then quit.

→ mpv --no-config --quiet --script=~/.mpv/scripts/test.lua test-panning-24fps.mp4
[test] observed: 1
Playing: test-panning-24fps.mp4
 (+) Video --vid=1 (*) (h264 1280x720 24.000fps)
VO: [opengl] 1280x720 yuv420p
[test] window-scale 1: 1.000000
[test] window-scale 2: 1.500000
[test] observed: 1.5
[test] window-scale 3: 1.000000


Exiting... (Quit)

With -v: https://gist.github.com/Argon-/e4c27a670fde61b4ac385e2a0ef6570c

Sample files

Works for me with every file tested, including pictures (don't forget keep-open in this case). I recommend a file that does not have a window-scale of 1 when normally opened and when in fullscreen, otherwise this bug is not noticeable.