fe2f5e1bf8
Alt+1..6 was a worse choice than the Alt+F-keys it replaced, and the reason
is the one that matters: anything the kernel swallows is taken from every
program that will ever run here, permanently.
Alt+<digit> is Meta-digit. zsh's own line editor binds it as digit-argument --
Alt+1 Alt+2 x repeats x twelve times -- and every readline editor does the
same. Yesterday's chord broke that system-wide, which is exactly the failure
mode of picking a chord applications want.
Working the whole space instead of one axis of it:
the HOST takes Alt+F4, Alt+F2, Ctrl+Alt+F1..F6
APPLICATIONS want Alt+anything (Meta), Ctrl+letter, Ctrl+Shift+digit
(Ctrl+Shift+2 types ^@), bare F-keys
the LAYOUT wants AltGr+letter -- Polish diacritics
Ctrl+Alt+Shift+F1..F6 is in none of those sets. Display managers bind the same
chord without Shift, so adding it steps out of the host's way, and no terminal
application binds a triple-modified function key.
Which chords actually reach a guest was measured rather than assumed: a
temporary probe in kbdgetc logged every modified keypress and QEMU's sendkey
fired each candidate at it. Everything reached the guest, Ctrl+Alt+F2
included -- so that conflict is the host's display manager, not QEMU. The same
probe corrected an earlier claim: `sendkey altgr-2` produces no event at all,
so the previous commit's "AltGr+2 did not fire" was never actually tested.
And the escape hatch is real now. VT_SETMODE was accepted and ignored, so a
program could ask to own the chord, be told yes, and still not get it.
VT_PROCESS genuinely stops the kernel switching. Together with the EVIOCGRAB
path -- which kbdgetc already checks before the chord is recognised -- there
are three honest layers: nothing, VT_PROCESS, exclusive grab.
What VT_PROCESS still does not do is the VT_RELDISP handshake; struct vt_mode
carries relsig/acqsig for when Schcom needs to release the GPU before the
screen changes hands.
Verified by screendump hash: Alt+2 reaches zsh as Meta, Ctrl+Alt+F2 and
Ctrl+Shift+F2 leave the screen untouched, Ctrl+Alt+Shift+F2 switches.
schfs-check passes.
Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01VQ7Qx8E1q1M1bbCq8QLHS2
155 lines
5.7 KiB
C
155 lines
5.7 KiB
C
// PC keyboard interface constants
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#define KBSTATP 0x64 // kbd controller status port(I)
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#define KBS_DIB 0x01 // kbd data in buffer
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#define KBDATAP 0x60 // kbd data port(I)
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#define NO 0
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#define SHIFT (1<<0)
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#define CTL (1<<1)
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#define ALT (1<<2)
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#define CAPSLOCK (1<<3)
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#define NUMLOCK (1<<4)
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#define SCROLLLOCK (1<<5)
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#define E0ESC (1<<6)
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// Right Alt, tracked apart from left Alt.
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//
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// They used to be the same bit, which is fine for typing -- neither is used to
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// look up a character -- and wrong for chords. On a Polish layout AltGr is how
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// you type a c e l n o s x z with their diacritics, and it is held constantly.
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// Nothing the kernel binds may involve it.
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#define RALT (1<<7)
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// Special keycodes
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#define KEY_HOME 0xE0
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#define KEY_END 0xE1
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#define KEY_UP 0xE2
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#define KEY_DN 0xE3
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#define KEY_LF 0xE4
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#define KEY_RT 0xE5
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#define KEY_PGUP 0xE6
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#define KEY_PGDN 0xE7
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#define KEY_INS 0xE8
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#define KEY_DEL 0xE9
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// Ctrl+Alt+Shift+F1..F6 -- switch virtual terminal.
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//
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// Above 0xFF deliberately. kbdgetc returns an int and consoleintr takes one,
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// and every value that fits in a byte is already either a character or a
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// UTF-8 continuation byte. A chord that collided with one would be typed into
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// the terminal instead of switching away from it.
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//
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// Choosing this took two wrong answers. Anything the kernel swallows is taken
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// from every program that will ever run here, permanently, and the obvious
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// candidates are all spoken for on one side or the other:
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//
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// HOST takes it, before the guest ever sees it
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// Alt+F4 the window manager closes the QEMU window
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// Alt+F2 GNOME and KDE open a run dialog
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// Ctrl+Alt+F1..F6 the display manager switches its *own* terminals
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//
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// APPLICATIONS want it, and would never get it again
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// Alt+<anything> Meta. zsh's own line editor binds Meta-digit as
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// digit-argument; every readline editor does too
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// Ctrl+<letter> control characters
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// Ctrl+Shift+<digit> types a character -- Ctrl+Shift+2 is ^@
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// F1..F6 alone help, and whatever a full-screen program wants
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//
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// THE KEYBOARD LAYOUT wants it
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// AltGr+<letter> Polish diacritics, and on some setups AltGr is
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// delivered as Ctrl+Alt
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//
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// Ctrl+Alt+Shift+F1..F6 is in none of those sets. Display managers bind the
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// same chord *without* Shift, so adding it steps out of the host's way, and
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// no terminal application binds a triple-modified function key. Four keys is
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// more than one wants to press, which is correct for something done rarely
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// and deliberately -- and `chvt N` is there for everything else.
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#define KEY_VT_SWITCH 0x120
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#define SCAN_F1 0x3B // F1..F6 are scancodes 0x3B..0x40
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// C('A') == Control-A
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#define C(x) (x - '@')
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static uchar shiftcode[256] =
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{
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[0x1D] CTL,
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[0x2A] SHIFT,
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[0x36] SHIFT,
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[0x38] ALT,
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[0x9D] CTL,
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[0xB8] RALT // right Alt / AltGr -- see RALT above
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};
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static uchar togglecode[256] =
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{
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[0x3A] CAPSLOCK,
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[0x45] NUMLOCK,
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[0x46] SCROLLLOCK
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};
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static uchar normalmap[256] =
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{
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NO, 0x1B, '1', '2', '3', '4', '5', '6', // 0x00
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'7', '8', '9', '0', '-', '=', '\b', '\t',
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'q', 'w', 'e', 'r', 't', 'y', 'u', 'i', // 0x10
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'o', 'p', '[', ']', '\n', NO, 'a', 's',
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'd', 'f', 'g', 'h', 'j', 'k', 'l', ';', // 0x20
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'\'', '`', NO, '\\', 'z', 'x', 'c', 'v',
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'b', 'n', 'm', ',', '.', '/', NO, '*', // 0x30
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NO, ' ', NO, NO, NO, NO, NO, NO,
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NO, NO, NO, NO, NO, NO, NO, '7', // 0x40
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'8', '9', '-', '4', '5', '6', '+', '1',
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'2', '3', '0', '.', NO, NO, NO, NO, // 0x50
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[0x9C] '\n', // KP_Enter
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[0xB5] '/', // KP_Div
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[0xC8] KEY_UP, [0xD0] KEY_DN,
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[0xC9] KEY_PGUP, [0xD1] KEY_PGDN,
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[0xCB] KEY_LF, [0xCD] KEY_RT,
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[0x97] KEY_HOME, [0xCF] KEY_END,
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[0xD2] KEY_INS, [0xD3] KEY_DEL
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};
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static uchar shiftmap[256] =
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{
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NO, 033, '!', '@', '#', '$', '%', '^', // 0x00
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'&', '*', '(', ')', '_', '+', '\b', '\t',
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'Q', 'W', 'E', 'R', 'T', 'Y', 'U', 'I', // 0x10
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'O', 'P', '{', '}', '\n', NO, 'A', 'S',
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'D', 'F', 'G', 'H', 'J', 'K', 'L', ':', // 0x20
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'"', '~', NO, '|', 'Z', 'X', 'C', 'V',
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'B', 'N', 'M', '<', '>', '?', NO, '*', // 0x30
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NO, ' ', NO, NO, NO, NO, NO, NO,
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NO, NO, NO, NO, NO, NO, NO, '7', // 0x40
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'8', '9', '-', '4', '5', '6', '+', '1',
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'2', '3', '0', '.', NO, NO, NO, NO, // 0x50
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[0x9C] '\n', // KP_Enter
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[0xB5] '/', // KP_Div
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[0xC8] KEY_UP, [0xD0] KEY_DN,
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[0xC9] KEY_PGUP, [0xD1] KEY_PGDN,
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[0xCB] KEY_LF, [0xCD] KEY_RT,
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[0x97] KEY_HOME, [0xCF] KEY_END,
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[0xD2] KEY_INS, [0xD3] KEY_DEL
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};
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static uchar ctlmap[256] =
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{
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NO, NO, NO, NO, NO, NO, NO, NO,
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NO, NO, NO, NO, NO, NO, NO, NO,
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C('Q'), C('W'), C('E'), C('R'), C('T'), C('Y'), C('U'), C('I'),
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C('O'), C('P'), NO, NO, '\r', NO, C('A'), C('S'),
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C('D'), C('F'), C('G'), C('H'), C('J'), C('K'), C('L'), NO,
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NO, NO, NO, C('\\'), C('Z'), C('X'), C('C'), C('V'),
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C('B'), C('N'), C('M'), NO, NO, C('/'), NO, NO,
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[0x9C] '\r', // KP_Enter
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[0xB5] C('/'), // KP_Div
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[0xC8] KEY_UP, [0xD0] KEY_DN,
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[0xC9] KEY_PGUP, [0xD1] KEY_PGDN,
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[0xCB] KEY_LF, [0xCD] KEY_RT,
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[0x97] KEY_HOME, [0xCF] KEY_END,
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[0xD2] KEY_INS, [0xD3] KEY_DEL
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};
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