/etc/X11/app-defaults/XClipboard 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 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 | *Command*Font: 	-*-helvetica-bold-r-normal--*-120-*-*-*-*-iso8859-1
*Label*Font: 	-*-helvetica-bold-r-normal--*-120-*-*-*-*-iso8859-1
*Text*Font:	-*-courier-medium-r-normal--*-120-*-*-*-*-iso8859-1
*quit.label: 			Quit
*quit.top: 			ChainTop
*quit.bottom: 			ChainTop
*quit.left: 			ChainLeft
*quit.right: 			ChainLeft
*quit.translations:		#override \n\
				<Btn1Down>,<Btn1Up>:Quit() unset()
*delete.label: 			Delete
*delete.fromHoriz: 		quit
*delete.top: 			ChainTop
*delete.bottom:			ChainTop
*delete.left:			ChainLeft
*delete.right:			ChainLeft
*delete.translations:		#override \n\
				<Btn1Down>,<Btn1Up>:DeleteClip() unset()
*new.label: 			New
*new.fromHoriz: 		delete
*new.top: 			ChainTop
*new.bottom:			ChainTop
*new.left:			ChainLeft
*new.right:			ChainLeft
*new.translations:		#override \n\
				<Btn1Down>,<Btn1Up>:NewClip() unset()
*save.label: 			Save
*save.fromHoriz: 		new
*save.top: 			ChainTop
*save.bottom:			ChainTop
*save.left:			ChainLeft
*save.right:			ChainLeft
*save.translations:		#override \n\
				<Btn1Down>,<Btn1Up>:Save() unset()
*next.label: 			Next
*next.fromHoriz: 		save
*next.top: 			ChainTop
*next.bottom:			ChainTop
*next.left:			ChainLeft
*next.right:			ChainLeft
*next.translations:		#override \n\
				<Btn1Down>,<Btn1Up>:NextClip() unset()
*prev.label: 			Prev
*prev.fromHoriz: 		next
*prev.top: 			ChainTop
*prev.bottom:			ChainTop
*prev.left:			ChainLeft
*prev.right:			ChainLeft
*prev.translations:		#override \n\
				<Btn1Down>,<Btn1Up>:PrevClip() unset()
*index.fromHoriz:		prev
*index.top: 			ChainTop
*index.bottom:			ChainTop
*index.left:			ChainLeft
*index.right:			ChainLeft
*index.resizable:		true
*text.scrollVertical:  		WhenNeeded
*text.scrollHorizontal:  	WhenNeeded
*text.autoFill: 		on
*text.fromVert: 		quit
*text.top: 			ChainTop
*text.bottom: 			ChainBottom
*text.left: 			ChainLeft
*text.right: 			ChainRight
*text.resizable:		true
*text.width:			300
XClipboard.geometry:		300x200
*ShapeStyle:			oval
XClipboard.baseTranslations: #augment\n\
			<Message>WM_PROTOCOLS: WMProtocols()\n
*TransientShell.baseTranslations: #augment\n\
			<Message>WM_PROTOCOLS: WMProtocols()\n
*fileDialog.label:			Save to file:
*fileDialog.label.top:			ChainTop
*fileDialog.label.bottom:		ChainTop
*fileDialog.label.left:			ChainLeft
*fileDialog.label.right:		ChainLeft
*fileDialogShell.allowShellResize:	true
*fileDialogShell.title:			File Save
*fileDialog*accept.label:		Accept
*fileDialog.accept.top:			ChainTop
*fileDialog.accept.bottom:		ChainBottom
*fileDialog.accept.left:		ChainLeft
*fileDialog.accept.right:		ChainLeft
*fileDialog*accept.translations:	#override\
			<BtnUp>: AcceptSave() unset()
*fileDialog.value.top:			ChainTop
*fileDialog.value.bottom:		ChainTop
*fileDialog.value.left:			ChainLeft
*fileDialog.value.right:		ChainLeft
*fileDialog*value.translations:	#override\
			<Key>Return: AcceptSave() \n\
			Ctrl<Key>S: no-op(ring-bell) \n\
			Ctrl<Key>R: no-op(ring-bell) \n\
			Ctrl<Key>M: no-op(ring-bell) \n\
			Ctrl<Key>J: no-op(ring-bell) \n\
			Meta<Key>I: no-op(ring-bell)
*fileDialog*value.baseTranslations:	#override\
			<Key>Return: AcceptSave() \n\
			Ctrl<Key>S: no-op(ring-bell) \n\
			Ctrl<Key>R: no-op(ring-bell) \n\
			Ctrl<Key>M: no-op(ring-bell) \n\
			Ctrl<Key>J: no-op(ring-bell) \n\
			Meta<Key>I: no-op(ring-bell)
*fileDialog*cancel.label:		Cancel
*fileDialog.cancel.top:			ChainTop
*fileDialog.cancel.bottom:		ChainBottom
*fileDialog.cancel.left:		ChainLeft
*fileDialog.cancel.right:		ChainLeft
*fileDialog*cancel.translations:	#override\
			<BtnUp>:CancelSave() unset()
*failDialog*Label.resizable:		true
*failDialog.label:			Can't write file
*failDialogShell.title:			Error
*failDialogShell.allowShellResize:	true
*failDialog*continue.label:		Continue
*failDialog*continue.translations:	#override\
			<BtnUp>:FailContinue() unset()
*failDialog*value.translations:	#override\
			<Key>Return: FailContinue() \n\
			Ctrl<Key>S: no-op(ring-bell) \n\
			Ctrl<Key>R: no-op(ring-bell) \n\
			Ctrl<Key>M: no-op(ring-bell) \n\
			Ctrl<Key>J: no-op(ring-bell) \n\
			Meta<Key>I: no-op(ring-bell)
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