alacritty: opacity doesn't work inside VM

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I can set background transparent in both kitty and xfce4-terminal, but the background_opacity in alacritty.yml file doesn’t work at all.

BTW: I got two environments, Manjaro+XFCE running inside VMware(Windows10 Host), Manjaro+KDE running without VMware, on two computers. Manjaro+XFCE running inside VMware(Windows10 host), background_opacity for alacritty doesn’t work at all. Manjaro+KDE running without VMware, background_opacity for alacritty works OK.

System

OS: Linux/BSD/macOS/Windows 5.7.15-1-MANJARO Version: alacritty --version output alacritty 0.5.0 Linux/BSD: X11/Wayland, DE or Compositor and WM XFCE4 Windows: WinPTY/ConPTY (see alacritty -v output)

Logs

NOTE: the ~/.alacritty.yml is the copied from /usr/share/doc/alacritty/example/alacritty.yml, the only difference is I changed background_opacity

Crashes: STDERR, STDOUT Font/Terminal size: alacritty -vv

eated log file at "/tmp/Alacritty-1961526.log"
[2020-09-10 10:21:15.553313074] [INFO] Welcome to Alacritty
[2020-09-10 10:21:15.553582044] [INFO] Configuration loaded from "/home/chz/.alacritty.yml"
[2020-09-10 10:21:15.572579550] [DEBUG] Estimated DPR: 1
[2020-09-10 10:21:15.572720799] [DEBUG] Estimated Cell Size: 9 x 17
[2020-09-10 10:21:15.572767342] [DEBUG] Estimated Dimensions: None
libEGL warning: DRI2: failed to authenticate
[2020-09-10 10:21:15.658639489] [INFO] Device pixel ratio: 1
[2020-09-10 10:21:15.675633080] [INFO] Initializing glyph cache...
[2020-09-10 10:21:15.708702490] [INFO] ... finished initializing glyph cache in 0.032946838s
[2020-09-10 10:21:15.708802355] [INFO] Cell Size: 9 x 17
[2020-09-10 10:21:15.708841802] [INFO] Padding: 0 x 0
[2020-09-10 10:21:15.708881409] [INFO] Width: 800, Height: 600
[2020-09-10 10:21:15.712123004] [INFO] PTY dimensions: Line(35) x Column(88)
[2020-09-10 10:21:15.734415167] [INFO] Initialisation complete
[2020-09-10 10:21:15.749278870] [DEBUG] Term::resize dimensions unchanged
[2020-09-10 10:21:15.749553916] [INFO] Width: 800, Height: 600

Keyboard and bindings: alacritty --print-events

Info: the left one is xfce4-terminal(transparent=0.5 in its Preferences), the middle one is alacritty with background_opacity=0.0, the right one is alacritty with background_opacity=1.0, you can see that changing background_opacity has some effect, just not transparent as expected.