/* [From our public header files: just hand us a pointer!]
 * Under WinNT/9x this defaults to gcMSWinIdleTest; otherwise
 * it starts null and must be aimed by the user. Only used by 
 * gcAttemptCollection and gcEnablePseudoIncremental. */
GC_API_VAR gcIdleTestFunction gcIdleTest;
 ...
/* Some sample idle test functions */
GC_API_FUN_DEF(int) gcXIdleTest(void)
{
    return !XEventsQueued( display, QueuedAfterFlush );
}
GC_API_FUN_DEF(int) gcMSWinIdleTest(void)
{
    MSG msg;
    return !PeekMessage(&msg, NULL, 0, 0, PM_NOREMOVE);
}

Example 1: An idle test function.