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// xkbcat: Logs X11 keypresses, globally.
#include <X11/XKBlib.h>
#include <string.h>
#include <stdio.h>
#include <stdlib.h>
#include <stdbool.h>
#include <time.h>
const char * DEFAULT_DISPLAY = ":0";
const int DEFAULT_DELAY = 10000000;
const bool DEFAULT_PRINT_UP = false;
const bool DEFAULT_PRINT_TIME = false;
typedef char KbBuffer[32];
static inline bool keyState(KbBuffer b, int key) {
// Fetch the `key`-th bit from the buffer.
return b[key/8] & (1<<(key%8));
// This is because XQueryKeymap just writes a bit per key into the buffer.
// Assuming 8-bit chars here, of course.
}
int printUsage() {
printf("\
USAGE: xkbcat [-display <display>] [-delay <nanosec>] [-up] [-time]\n\
display target X display (default %s)\n\
delay polling frequency; nanoseconds (default %d)\n\
up also print key-ups (default %s)\n\
time also print timestamps (default %s)\n",
DEFAULT_DISPLAY, DEFAULT_DELAY,
(DEFAULT_PRINT_UP ? "yes" : "no"),
(DEFAULT_PRINT_TIME ? "yes" : "no") );
exit(0);
}
// Since `XKeysymToString` returns a string of unknown length that shouldn't be
// modified, so it makes more sense to just `printf` it in-place.
void printKeyPress(Display * disp, int code, bool down, bool printKeyUps, long timestamp, bool printTimes) {
KeySym s = XkbKeycodeToKeysym(disp, code, 0, 0); if (NoSymbol == s) return;
char * str = XKeysymToString(s); if (NULL == str) return;
if (printKeyUps) printf("%s ", (down ? "+" : "-"));
printf("%s", str);
if (printTimes) printf(" %ld", timestamp);
printf("\n");
}
int main(int argc, char * argv[]) {
const char * hostname = DEFAULT_DISPLAY;
int delay = DEFAULT_DELAY;
bool printKeyUps = DEFAULT_PRINT_UP;
bool printTimes = DEFAULT_PRINT_TIME;
// Get arguments
for (int i = 1; i < argc; i++) {
if (!strcmp(argv[i], "-help")) printUsage();
else if (!strcmp(argv[i], "-display")) hostname = argv[++i];
else if (!strcmp(argv[i], "-delay")) delay = atoi(argv[++i]);
else if (!strcmp(argv[i], "-up")) printKeyUps = true;
else if (!strcmp(argv[i], "-time")) printTimes = true;
else { printf("Unexpected argument `%s`\n", argv[i]); printUsage(); }
}
// Set up X
Display * disp = XOpenDisplay(hostname);
if (NULL == disp) {
fprintf(stderr, "Cannot open X display: %s\n", hostname);
exit(1);
}
XSynchronize(disp, true);
// Set up buffers
KbBuffer keyBuffer1, keyBuffer2;
KbBuffer * oldKeys = &keyBuffer1,
* keys = &keyBuffer2;
XQueryKeymap(disp, *oldKeys); // Initial fetch
// Timespec for time to sleep for
struct timespec sleepTime = { .tv_nsec = delay };
while (1) { // Forever
XQueryKeymap(disp, *keys); // Fetch changed keys
long timestamp = 0;
if (printTimes) timestamp = (long)time(NULL);
for (int i = 0; i < sizeof(KbBuffer) * 8; i++) {
bool stateBefore = keyState(*oldKeys, i),
stateNow = keyState(*keys, i);
if ( stateNow != stateBefore // Changed?
&& (stateNow || printKeyUps) ) // Should print?
printKeyPress(disp, i, stateNow, printKeyUps, timestamp, printTimes);
}
{ // Swap buffers
KbBuffer * temp = oldKeys;
oldKeys = keys;
keys = temp;
}
nanosleep(&sleepTime, NULL);
}
}
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