我的计算机是 Ubuntu 18.04 LTS，带有 Linux 内核 5.0.0-23-generic。
我将Shift_R键重新映射到 a Mode_switch,
clear Shift
keycode 50 = Shift_L NoSymbol Shift_L
keycode 62 = Mode_switch NoSymbol Mode_switch
add Shift = Shift_L
以及一些Shift_L-Shift_R-<key>符号键，例如，
keycode 41 = i I I braceleft
keycode 53 = t T T grave
尽管其中一些效果很好，但另一些则不然。
例如，Shift_L-Shift_R-F(keycode 41) 打印{（正确），而Shift_L-Shift_R-X(keycode 53) 不打印任何内容。
所以我跑起来xev并按下Shift_L（键码50），Shift_R（键码62），X（键码53）：
$ xev
KeyPress event, serial 37, synthetic NO, window 0x4000001,
root 0x31c, subw 0x0, time 3610499, (1273,328), root:(1347,399),
state 0x0, keycode 50 (keysym 0xffe1, Shift_L), same_screen YES,
XLookupString gives 0 bytes:
XmbLookupString gives 0 bytes:
XFilterEvent returns: False
KeyPress event, serial 37, synthetic NO, window 0x4000001,
root 0x31c, subw 0x0, time 3611315, (1273,328), root:(1347,399),
state 0x1, keycode 62 (keysym 0xff7e, Mode_switch), same_screen YES,
XLookupString gives 0 bytes:
XmbLookupString gives 0 bytes:
XFilterEvent returns: False
KeyRelease event, serial 37, synthetic NO, window 0x4000001,
root 0x31c, subw 0x0, time 3612803, (1273,328), root:(1347,399),
state 0x2001, keycode 50 (keysym 0xffe1, Shift_L), same_screen YES,
XLookupString gives 0 bytes:
XFilterEvent returns: False
KeyRelease event, serial 37, synthetic NO, window 0x4000001,
root 0x31c, subw 0x0, time 3612803, (1273,328), root:(1347,399),
state 0x2000, keycode 62 (keysym 0xff7e, Mode_switch), same_screen YES,
XLookupString gives 0 bytes:
XFilterEvent returns: False
然后以相反的顺序释放：
KeyPress event, serial 37, synthetic NO, window 0x4000001,
root 0x31c, subw 0x0, time 3614962, (1273,328), root:(1347,399),
state 0x0, keycode 50 (keysym 0xffe1, Shift_L), same_screen YES,
XLookupString gives 0 bytes:
XmbLookupString gives 0 bytes:
XFilterEvent returns: False
KeyPress event, serial 37, synthetic NO, window 0x4000001,
root 0x31c, subw 0x0, time 3614962, (1273,328), root:(1347,399),
state 0x1, keycode 62 (keysym 0xff7e, Mode_switch), same_screen YES,
XLookupString gives 0 bytes:
XmbLookupString gives 0 bytes:
XFilterEvent returns: False
KeyRelease event, serial 37, synthetic NO, window 0x4000001,
root 0x31c, subw 0x0, time 3616673, (1273,328), root:(1347,399),
state 0x2001, keycode 62 (keysym 0xff7e, Mode_switch), same_screen YES,
XLookupString gives 0 bytes:
XFilterEvent returns: False
KeyRelease event, serial 37, synthetic NO, window 0x4000001,
root 0x31c, subw 0x0, time 3617441, (1273,328), root:(1347,399),
state 0x1, keycode 50 (keysym 0xffe1, Shift_L), same_screen YES,
XLookupString gives 0 bytes:
XFilterEvent returns: False
Shift_L并Shift_R于何时释放Shift_L-Shift_R-X？
xmodmap与默认值相比的所有更改是：
clear Shift
keycode 20 = minus question question underscore
keycode 24 = v V V V
keycode 25 = k K K K
keycode 26 = r R R R
keycode 27 = y Y Y Y
keycode 28 = q Q Q Q
keycode 29 = x X X X
keycode 30 = a A A A
keycode 31 = f F F F
keycode 32 = u U U U
keycode 33 = d D D D
keycode 34 = z Z Z Z
keycode 35 = dollar asciicircum asciicircum dollar
keycode 36 = slash Escape Escape slash
keycode 38 = h H H H
keycode 39 = j J J plus
keycode 40 = l L L bracketleft
keycode 41 = i I I braceleft
keycode 42 = semicolon apostrophe apostrophe parenleft
keycode 43 = colon quotedbl quotedbl parenright
keycode 44 = o O O braceright
keycode 45 = s S S bracketright
keycode 46 = e E E asterisk
keycode 47 = g G G G
keycode 48 = b B B B
keycode 49 = grave asciitilde asciitilde grave
keycode 51 = backslash bar bar backslash
keycode 52 = m M M M
keycode 53 = t T T grave
keycode 54 = n N N numbersign
keycode 55 = BackSpace backslash backslash BackSpace
keycode 56 = comma less less equal
keycode 57 = period greater greater minus
keycode 58 = Return underscore underscore Return
keycode 59 = c C C percent
keycode 60 = w W W asciitilde
keycode 61 = p P P P
keycode 62 = Mode_switch NoSymbol Mode_switch
add Shift = Shift_L
Well-keys（比如Shift_L-Shift_R-F变成{）是
- 20、24、25、26、27、30、31、32、33、38、39、40、41、42、43、44、45、46、47、48、49、51、56、57、61。
错误的键（如Shift_L-Shift_R-XreleasesShift_L和Shift_R）是
- 28、29、34、35、36、52、53、54、55、58、59、60。
这两种类型的密钥有何不同？
我该如何解决这种奇怪的行为？