cspotcode
commented
6 years ago I believe that these issues are caused by the way ConEmu sends bytes to the target executable's stdin. When the ANSI sequences get split up over multiple read() calls, the target program doesn't necessarily wait for the full ANSI sequence to arrive, so the target program interprets the left arrow key as its constituent parts: "Escape", "[", "C".
I informally tested this by writing a simple C program that calls read() in a loop and logs the results. So as you hit keyboard keys, it logs the bytes of each keystroke, one read() call per line.
When running bash without ConEmu, keystrokes are never split up across multiple read calls. But within ConEmu, they are occasionally split up.
Here's the code. You can save as main.c, compile with gcc main.c, and then run it: stty -icanon -echo ; ./a.out Hold down a key and watch the program read them from stdin. Try it in bash and then again in bash within ConEmu. (stty is required to turn off the tty's echo and canonical modes. Note this will suppress character output after you Ctrl+C out of the program; this is not a bug; stty echo to turn it back on)
#include <unistd.h>
#include <stdio.h>
int main(int argc, char** argv) {
char buffer[100];
while(1) {
ssize_t count = read(0, buffer, 100);
for(int i = 0; i < count; i++) {
printf("%#02x ", buffer[i]);
}
printf("\n");
}
}My workaround for this problem is an expect script that uses interact mode with a regexp that matches ANSI key sequences. It effectively buffers them and sends them to the target executable all at once, so that ANSI sequences don't get split.
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Versions
ConEmu build: 180626 x64 OS version: Windows 10 x32/x64 Used shell version: bash.exe from WSL(debian)
Problem description
Sometimes arrow keys(and PgUp, PgDn) do not move the cursur, but prints symbols. It appears only with ConEmu, but when I run bash.exe directly from Windows I have no problems.
Steps to reproduce
Actual results
Arrow keys sometimes prints symbols(A,B,C,D).
Expected results
Arrow keys just moving cursor in editor.
Additional files