Switching workspaces on KDE or a wlroots compositor hides the toplevel
without any GTK visibility change, and the compositor stops answering
the video plane's frame callbacks. Once the ack watchdog spent its miss
budget it stopped dead: the giveup destroyed the only outstanding
wl_callback, mpv's edge-triggered redraw latch was already saturated by
a render that bailed on frame_pending(), and no visibility change ever
comes - so video stayed frozen on the last buffer until a resize or
fullscreen toggle, while audio kept playing.
Back off to a slow re-present timer instead of stopping. A present only
happens when mpv actually has a new frame, so a hidden playing plane
settles at one commit per ~1.5 s and recovers within a second of being
shown again; a paused hidden plane goes dormant and is revived by mpv's
next update edge.
close#2067
edde746
6f64ca2952