7c0f7c7d01
Third guess at a chord, and the third one would have been wrong too: a display
manager that grabs Ctrl+Alt+F<n> matches loosely, so Ctrl+Alt+Shift+F2 never
reaches the guest either. Extra modifiers do not get past a loose grab.
The real problem is that this is not knowable from inside. A key the host
swallowed is indistinguishable from a key nobody pressed, so the guest cannot
probe for a free combination, and there is no combination that is free
everywhere:
the HOST takes Alt+F4, Alt+F2, Ctrl+Alt+F1..F6 (loosely matched),
Ctrl+Alt+digit (QEMU's own console tabs)
APPLICATIONS want Alt+anything (Meta -- zsh binds Meta-digit as
digit-argument), Ctrl+letter, Ctrl+Shift+digit
(Ctrl+Shift+2 types ^@), bare F-keys
the LAYOUT wants AltGr+letter
So it is a setting. VT_SETCHORD/VT_GETCHORD, and in userspace:
chvt -c ctrl+shift+F Ctrl+Shift+F1..F6 (the new default)
chvt -c ctrl+alt+shift+F
chvt -c alt+1
chvt -c off no chord; chvt N is then the only way
chvt report the active terminal and the chord
`off` is a legitimate setting rather than a failure mode. On a machine whose
host grabs everything worth binding, `chvt N` is the honest answer.
The default moved to Ctrl+Shift+F1..F6: display managers bind Ctrl+Alt+F<n>,
not Ctrl+Shift+F<n>, and Ctrl+Shift with a *function* key is not a character
on any layout -- unlike Ctrl+Shift+digit, which is.
Caught while writing it: VTC_RALT was 0x08 while kbd.h's RALT is (1<<7), since
(1<<3) is CAPSLOCK. A chord set from userspace with AltGr would simply never
have matched, and the only symptom would have been a key that does nothing.
A _Static_assert now holds the two headers together.
Verified: Ctrl+Alt+F2 leaves the screen byte-identical, Ctrl+Shift+F2 switches,
Ctrl+Shift+F1 returns to a pixel-identical tty1, and chvt -c round-trips
through alt+1 and off and back. schfs-check passes.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VQ7Qx8E1q1M1bbCq8QLHS2
158 lines
5.8 KiB
C
158 lines
5.8 KiB
C
// PC keyboard interface constants
|
|
|
|
#define KBSTATP 0x64 // kbd controller status port(I)
|
|
#define KBS_DIB 0x01 // kbd data in buffer
|
|
#define KBDATAP 0x60 // kbd data port(I)
|
|
|
|
#define NO 0
|
|
|
|
#define SHIFT (1<<0)
|
|
#define CTL (1<<1)
|
|
#define ALT (1<<2)
|
|
|
|
#define CAPSLOCK (1<<3)
|
|
#define NUMLOCK (1<<4)
|
|
#define SCROLLLOCK (1<<5)
|
|
|
|
#define E0ESC (1<<6)
|
|
|
|
// Right Alt, tracked apart from left Alt.
|
|
//
|
|
// They used to be the same bit, which is fine for typing -- neither is used to
|
|
// look up a character -- and wrong for chords. On a Polish layout AltGr is how
|
|
// you type a c e l n o s x z with their diacritics, and it is held constantly.
|
|
// Nothing the kernel binds may involve it.
|
|
#define RALT (1<<7)
|
|
|
|
// Special keycodes
|
|
#define KEY_HOME 0xE0
|
|
#define KEY_END 0xE1
|
|
#define KEY_UP 0xE2
|
|
#define KEY_DN 0xE3
|
|
#define KEY_LF 0xE4
|
|
#define KEY_RT 0xE5
|
|
#define KEY_PGUP 0xE6
|
|
#define KEY_PGDN 0xE7
|
|
#define KEY_INS 0xE8
|
|
#define KEY_DEL 0xE9
|
|
|
|
// Switch virtual terminal.
|
|
//
|
|
// Above 0xFF deliberately. kbdgetc returns an int and consoleintr takes one,
|
|
// and every value that fits in a byte is already either a character or a
|
|
// UTF-8 continuation byte. A chord that collided with one would be typed into
|
|
// the terminal instead of switching away from it.
|
|
//
|
|
// *Which* chord is a runtime setting, not a constant here, and that is the
|
|
// interesting part. Three separate parties have a claim on every candidate:
|
|
//
|
|
// the HOST, which sees the keystroke first and may never pass it on
|
|
// Alt+F4, Alt+F2 window manager
|
|
// Ctrl+Alt+F1..F6 display manager, and it matches loosely --
|
|
// adding Shift does not get past it
|
|
// Ctrl+Alt+<digit> QEMU's own console tabs
|
|
//
|
|
// APPLICATIONS, which lose the key permanently if the kernel eats it
|
|
// Alt+<anything> Meta. zsh binds Meta-digit as digit-argument
|
|
// Ctrl+<letter> control characters
|
|
// Ctrl+Shift+<digit> types a character -- Ctrl+Shift+2 is ^@
|
|
// F1..F6 alone help, and full-screen programs
|
|
//
|
|
// the KEYBOARD LAYOUT
|
|
// AltGr+<letter> Polish diacritics, and on some setups AltGr
|
|
// arrives as Ctrl+Alt
|
|
//
|
|
// There is no combination that is free for everyone on every host, and the
|
|
// guest cannot find out what its host grabs -- the keystroke simply never
|
|
// arrives, which is indistinguishable from a chord nobody pressed. So the
|
|
// kernel ships a default and lets it be changed: VT_SETCHORD, and `chvt
|
|
// --chord` in userspace. Setting it to no modifiers disables the chord
|
|
// entirely and leaves `chvt N` as the only way to switch, which is a
|
|
// legitimate choice on a machine whose host takes everything.
|
|
#define KEY_VT_SWITCH 0x120
|
|
|
|
#define SCAN_F1 0x3B // F1..F6 are scancodes 0x3B..0x40
|
|
#define SCAN_1 0x02 // 1..6 are scancodes 0x02..0x07
|
|
|
|
// C('A') == Control-A
|
|
#define C(x) (x - '@')
|
|
|
|
static uchar shiftcode[256] =
|
|
{
|
|
[0x1D] CTL,
|
|
[0x2A] SHIFT,
|
|
[0x36] SHIFT,
|
|
[0x38] ALT,
|
|
[0x9D] CTL,
|
|
[0xB8] RALT // right Alt / AltGr -- see RALT above
|
|
};
|
|
|
|
static uchar togglecode[256] =
|
|
{
|
|
[0x3A] CAPSLOCK,
|
|
[0x45] NUMLOCK,
|
|
[0x46] SCROLLLOCK
|
|
};
|
|
|
|
static uchar normalmap[256] =
|
|
{
|
|
NO, 0x1B, '1', '2', '3', '4', '5', '6', // 0x00
|
|
'7', '8', '9', '0', '-', '=', '\b', '\t',
|
|
'q', 'w', 'e', 'r', 't', 'y', 'u', 'i', // 0x10
|
|
'o', 'p', '[', ']', '\n', NO, 'a', 's',
|
|
'd', 'f', 'g', 'h', 'j', 'k', 'l', ';', // 0x20
|
|
'\'', '`', NO, '\\', 'z', 'x', 'c', 'v',
|
|
'b', 'n', 'm', ',', '.', '/', NO, '*', // 0x30
|
|
NO, ' ', NO, NO, NO, NO, NO, NO,
|
|
NO, NO, NO, NO, NO, NO, NO, '7', // 0x40
|
|
'8', '9', '-', '4', '5', '6', '+', '1',
|
|
'2', '3', '0', '.', NO, NO, NO, NO, // 0x50
|
|
[0x9C] '\n', // KP_Enter
|
|
[0xB5] '/', // KP_Div
|
|
[0xC8] KEY_UP, [0xD0] KEY_DN,
|
|
[0xC9] KEY_PGUP, [0xD1] KEY_PGDN,
|
|
[0xCB] KEY_LF, [0xCD] KEY_RT,
|
|
[0x97] KEY_HOME, [0xCF] KEY_END,
|
|
[0xD2] KEY_INS, [0xD3] KEY_DEL
|
|
};
|
|
|
|
static uchar shiftmap[256] =
|
|
{
|
|
NO, 033, '!', '@', '#', '$', '%', '^', // 0x00
|
|
'&', '*', '(', ')', '_', '+', '\b', '\t',
|
|
'Q', 'W', 'E', 'R', 'T', 'Y', 'U', 'I', // 0x10
|
|
'O', 'P', '{', '}', '\n', NO, 'A', 'S',
|
|
'D', 'F', 'G', 'H', 'J', 'K', 'L', ':', // 0x20
|
|
'"', '~', NO, '|', 'Z', 'X', 'C', 'V',
|
|
'B', 'N', 'M', '<', '>', '?', NO, '*', // 0x30
|
|
NO, ' ', NO, NO, NO, NO, NO, NO,
|
|
NO, NO, NO, NO, NO, NO, NO, '7', // 0x40
|
|
'8', '9', '-', '4', '5', '6', '+', '1',
|
|
'2', '3', '0', '.', NO, NO, NO, NO, // 0x50
|
|
[0x9C] '\n', // KP_Enter
|
|
[0xB5] '/', // KP_Div
|
|
[0xC8] KEY_UP, [0xD0] KEY_DN,
|
|
[0xC9] KEY_PGUP, [0xD1] KEY_PGDN,
|
|
[0xCB] KEY_LF, [0xCD] KEY_RT,
|
|
[0x97] KEY_HOME, [0xCF] KEY_END,
|
|
[0xD2] KEY_INS, [0xD3] KEY_DEL
|
|
};
|
|
|
|
static uchar ctlmap[256] =
|
|
{
|
|
NO, NO, NO, NO, NO, NO, NO, NO,
|
|
NO, NO, NO, NO, NO, NO, NO, NO,
|
|
C('Q'), C('W'), C('E'), C('R'), C('T'), C('Y'), C('U'), C('I'),
|
|
C('O'), C('P'), NO, NO, '\r', NO, C('A'), C('S'),
|
|
C('D'), C('F'), C('G'), C('H'), C('J'), C('K'), C('L'), NO,
|
|
NO, NO, NO, C('\\'), C('Z'), C('X'), C('C'), C('V'),
|
|
C('B'), C('N'), C('M'), NO, NO, C('/'), NO, NO,
|
|
[0x9C] '\r', // KP_Enter
|
|
[0xB5] C('/'), // KP_Div
|
|
[0xC8] KEY_UP, [0xD0] KEY_DN,
|
|
[0xC9] KEY_PGUP, [0xD1] KEY_PGDN,
|
|
[0xCB] KEY_LF, [0xCD] KEY_RT,
|
|
[0x97] KEY_HOME, [0xCF] KEY_END,
|
|
[0xD2] KEY_INS, [0xD3] KEY_DEL
|
|
};
|
|
|