After 2.17.1 the video went fully black on Windows for as long as the player
UI was on screen and came back the instant it faded out. Audio was never
affected, mpv.conf made no difference, and 2.17.0 on the same machine and
driver was fine.
2.17.1 moved to Flutter 3.47.1, which made Impeller the default Windows
renderer. Plezy is unusually exposed to that switch: the patched engine
presents the UI on a topmost DirectComposition visual that DWM blends over the
mpv video child, so the video is only as visible as the presented frame's
per-pixel alpha says it is. When Impeller's GLES backend gets that alpha wrong,
the OSD's full-screen scrim presents opaque and hides the video outright;
unmounting the controls presents a transparent frame again, which is why the
picture tracked the UI exactly.
Opt out through the embedder Impeller switch that 3.47 added. Unlike
FLUTTER_ENGINE_SWITCHES it applies to release builds, and it restores the
renderer every release up to 2.17.0 shipped without touching the engine patches.
close#2127
edde746