From a76193c684a9ad4f907038172d7bb33694c41a9e Mon Sep 17 00:00:00 2001
From: Cody Hiar <cody@hiar.ca>
Date: Sat, 19 Oct 2019 15:45:18 -0600
Subject: Initial commit

---
 keyboard_reader.c | 80 +++++++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 80 insertions(+)
 create mode 100644 keyboard_reader.c

(limited to 'keyboard_reader.c')

diff --git a/keyboard_reader.c b/keyboard_reader.c
new file mode 100644
index 0000000..319f702
--- /dev/null
+++ b/keyboard_reader.c
@@ -0,0 +1,80 @@
+// xkbcat: Logs X11 keypresses, globally.
+
+#include <X11/XKBlib.h>
+#include <X11/extensions/XInput2.h>
+
+#include <string.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <stdbool.h>
+
+const char * DEFAULT_DISPLAY    = ":0";
+const bool   DEFAULT_PRINT_UP   = false;
+
+char * get_key() {
+
+    const char * hostname    = DEFAULT_DISPLAY;
+    bool         printKeyUps = DEFAULT_PRINT_UP;
+
+    // Set up X
+    Display * disp = XOpenDisplay(hostname);
+    if (NULL == disp) {
+        fprintf(stderr, "Cannot open X display: %s\n", hostname);
+        exit(1);
+    }
+
+    // Test for XInput 2 extension
+    int xi_opcode;
+    int queryEvent, queryError;
+    if (! XQueryExtension(disp, "XInputExtension", &xi_opcode,
+                &queryEvent, &queryError)) {
+        // XXX Test version >=2
+        fprintf(stderr, "X Input extension not available\n"); return "";
+    }
+
+    // Register events
+    Window root = DefaultRootWindow(disp);
+    XIEventMask m;
+    m.deviceid = XIAllMasterDevices;
+    m.mask_len = XIMaskLen(XI_LASTEVENT);
+    m.mask = calloc(m.mask_len, sizeof(char));
+    XISetMask(m.mask, XI_RawKeyPress);
+    XISetMask(m.mask, XI_RawKeyRelease);
+    XISelectEvents(disp, root, &m, 1);
+    XSync(disp, false);
+    free(m.mask);
+
+    while (1) { // Forever
+        XEvent event;
+        XGenericEventCookie *cookie = (XGenericEventCookie*)&event.xcookie;
+        XNextEvent(disp, &event);
+
+        if (XGetEventData(disp, cookie) &&
+                cookie->type == GenericEvent &&
+                cookie->extension == xi_opcode)
+        {
+            switch (cookie->evtype)
+            {
+                case XI_RawKeyRelease: if (!printKeyUps) continue;
+                case XI_RawKeyPress: {
+                    XIRawEvent *ev = cookie->data;
+
+                    // Ask X what it calls that key
+                    KeySym s = XkbKeycodeToKeysym(disp, ev->detail, 0, 0);
+                    if (NoSymbol == s) continue;
+                    char *str = XKeysymToString(s);
+                    if (NULL == str) continue;
+
+
+                    if (printKeyUps) printf("%s", cookie->evtype == XI_RawKeyPress ? "+" : "-");
+                    char *ret = malloc(1000);
+                    sprintf(ret, "%s", str);
+                    XCloseDisplay(disp);
+                    return ret;
+                    break;
+                                     }
+            }
+        }
+        fflush(stdout);
+    }
+}
-- 
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