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client: tighten CSI u detach key matching 

Restrict the kitty keyboard protocol detach matcher to better mirror
the legacy single-byte behavior:

- Only match key press events (:1 or absent), not repeat (:2) or
  release (:3).  In practice the press triggers detach before the
  release arrives, but this is more correct.

- Reject if shift, alt, super, hyper, or meta are also held.  The
  legacy byte for e.g. Ctrl-\ is distinct from Ctrl+Shift-\, so
  extra non-lock modifiers should not trigger detach.  Lock keys
  (numlock, capslock) are still allowed since they do not affect key
  identity.
This commit is contained in:
mgabor3141 2026-02-26 18:54:43 +01:00
parent 4d5cbf22c0
commit d6551eb226
1 changed files with 21 additions and 6 deletions
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27
client.c
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@ -86,8 +86,11 @@ static void init_csi_detach(void) {
}
/* Parse a CSI u sequence: ESC [ <number> ; <number> [: <number>] u
* Returns true if it encodes the detach key with ctrl modifier.
* Accepts any additional modifiers (numlock, capslock, etc.). */
* Returns true if it encodes the detach key with only the ctrl modifier
* (plus any lock keys like numlock/capslock).
*
* Does NOT match if shift, alt, or super are also held, mirroring the
* legacy behavior where only the exact control byte triggers detach. */
static bool is_csi_detach(const char *buf, ssize_t len) {
if (len < 6 || buf[0] != '\033' || buf[1] != '[')
return false;
@ -112,21 +115,33 @@ static bool is_csi_detach(const char *buf, ssize_t len) {
while (i < len && buf[i] >= '0' && buf[i] <= '9')
mod = mod * 10 + (buf[i++] - '0');
/* Skip optional event type (:1=press, :2=repeat, :3=release) */
/* Check optional event type — only match press (:1) or
* absent (implied press), not repeat (:2) or release (:3). */
if (i < len && buf[i] == ':') {
i++;
unsigned int event = 0;
while (i < len && buf[i] >= '0' && buf[i] <= '9')
i++;
event = event * 10 + (buf[i++] - '0');
if (event != 1)
return false;
}
/* Must end with 'u' */
if (i != len - 1)
return false;
/* Check ctrl is set: modifier = 1 + bitmask, ctrl = bit 2 (value 4) */
/* Modifier = 1 + bitmask. Check ctrl (bit 2) is set and no
* other non-lock modifiers (shift=1, alt=2, super=8, hyper=16,
* meta=32) are present. Lock keys (capslock=64, numlock=128)
* are allowed since they don't affect the key identity. */
if (mod < 1)
return false;
return ((mod - 1) & 4) != 0;
unsigned int bits = mod - 1;
if (!(bits & 4))
return false; /* ctrl not set */
if (bits & (1|2|8|16|32))
return false; /* shift, alt, super, hyper, or meta also held */
return true;
}
static int client_mainloop(void) {