Fix keyboard input latency (~100ms per keystroke) from VMIN=3/VTIME=1 - #63
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set_terminal() used VMIN=3 + VTIME=1 (interbyte-timer mode), introduced in 03baea1 to make arrow keys work under Cygwin. With VMIN=3, a single ordinary keystroke must wait for the 100ms interbyte timeout before read() returns, so typing feels sluggish (~0.1s per character). - set_terminal: switch to VMIN=1/VTIME=0 so each byte returns immediately - read_escape_tail(): after a lone ESC, drain trailing bytes within a short select() window so multi-byte sequences (arrow keys, Home/End) are still parsed as a single key instead of leaking control bytes ('[', 'A', ...) into the input line
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Problem
Typing in the VPCS console feels sluggish: each ordinary keystroke is delayed by roughly 100ms.
Root cause
set_terminal()puts the terminal in non-canonical mode withVMIN=3andVTIME=1(interbyte-timer mode). This was introduced in 03baea1 ("arrow keys is OK in cygwin") so that a 3-byte escape sequence such as an arrow key (\e[A) would be returned by a singleread().With
VMIN=3,read()blocks until it has collected 3 bytes or the interbyte timer (VTIME=1= 100ms) expires with no new byte arriving. A normal key produces only 1 byte, so every keystroke has to wait for the 100ms timeout before it is returned — hence the ~0.1s-per-character lag. (Escape sequences happen to be 3 bytes, which is why arrow keys did not feel laggy while ordinary typing did.)Fix
set_terminal(): switch toVMIN=1, VTIME=0so each byte is returned immediately.read_escape_tail(): after a loneESC, drain any trailing bytes arriving within a shortselect()window (50ms for the first byte, 10ms for subsequent ones), so multi-byte sequences (arrow keys, Home/End, ...) are still parsed as a single key instead of leaking their control bytes ([,A, ...) into the input line.This removes the per-character delay while preserving the arrow-key / Home / End / history behavior — the original reason
VMINwas raised.Verification
gcc -O2 -Wall; with-Wextrathere are no new warnings (the few-Wextrawarnings are pre-existing and unrelated).\x1b[A(Up arrow) underVMIN=1is recognized as a single key and does not leak[/Ainto the input line.