/etc/X11/app-defaults/Xmag is in x11-apps 7.7+4.
This file is owned by root:root, with mode 0o644.
The actual contents of the file can be viewed below.
| 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 | *Font: fixed
*pane2*orientation: horizontal
*pane2*showGrip: False
*allowShellResize: on
*Scale.baseTranslations:#augment\
			<EnterWindow>: set-colors()\n\
			<LeaveWindow>: unset-colors()\n\
			<Btn1Down>:popup-pixel()\n\
			Button1<Enter>:popup-pixel()\n\
			<Btn1Motion>:update-pixel()\n\
			<Btn1Up>:popdown-pixel()\n\
			<Leave>:popdown-pixel()\n\
			<Key>n:new()\n\
			<Key>q:close()\n\
			Ctrl<Key>c:close()\n\
			<Key>space:replace()
*close.accelerators:#augment\
			<Key>q:set()notify()unset()\n\
			Ctrl<Key>c:set()notify()unset()
*replace.accelerators:#augment\
			<Key>space:set()notify()unset()\n\
			<Btn2Up>:set()notify()unset()\n\
			<Btn3Up>:set()notify()unset()
*helpLabel.font:	8x13bold
*helpLabel.label:	xmag
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