core.vbs auto-wires Controller.Pause = True into every table's Paused
event, which Player::OnFocusChanged() fires on focus loss. PinMAME's
own pause handling in usrintrf.c is a "while (g_fPause) { ...;
draw_screen(); ... }" busy-wait written for a real-OS-thread host,
where a separate thread later flips g_fPause back to 0. Under our
single-threaded Emscripten cooperative-scheduling model there is no
second thread to clear it, so entering that loop spins forever at
100% CPU with the tab completely unresponsive.
cpu_run_emscripten_step() now checks g_fPause up front and skips
cpu_timeslice() (and therefore that loop) entirely while paused;
emulation simply doesn't advance until Controller.Pause is set back
to False and the step function is called again next frame.
Confirmed fixed by hands-on testing: unfocusing the browser during a
PinMAME ROM session no longer freezes the tab.
Co-Authored-By: Claude Sonnet 5 <noreply@anthropic.com>
valknarandClaude Sonnet 5
99ae5b9eda