-# "xscreensaver-getimage" will invoke this program, depending on the
-# value of the "grabDesktopImages" setting in the ~/.xscreensaver file
-# (or in /usr/lib/X11/app-defaults/XScreenSaver).
+# When running on non-Mac X11 systems, utils/grabscreen.c is used.
+#
+# However, when running under X11 on MacOS, that usual X11-based
+# screen-grabbing mechanism doesn't work, so we need to invoke the
+# "/usr/bin/screencapture" program to do it instead. (This script).
+#
+# However again, for the MacOS-native (Cocoa) build of the screen savers,
+# "utils/grabclient.c" instead links against "OSX/osxgrabscreen.m", which
+# grabs screen images directly without invoking a sub-process to do it.