Rewrite linux global hotkey to not depend on any libraries (also allows it to work on non-systemd systems(?)), remove unused gsr-window-name

tools/gsr-global-hotkeys/hotplug.c

@@ -0,0 +1,76 @@
+#include "hotplug.h"
+
+/* C stdlib */
+#include <string.h>
+
+/* POSIX */
+#include <unistd.h>
+#include <sys/socket.h>
+
+/* LINUX */
+#include <linux/types.h>
+#include <linux/netlink.h>
+
+bool hotplug_event_init(hotplug_event *self) {
+    memset(self, 0, sizeof(*self));
+
+    struct sockaddr_nl nls = {
+        .nl_family = AF_NETLINK,
+        .nl_pid = getpid(),
+        .nl_groups = -1
+    };
+
+    const int fd = socket(PF_NETLINK, SOCK_DGRAM, NETLINK_KOBJECT_UEVENT);
+    if(fd == -1)
+        return false; /* Not root user */
+
+    if(bind(fd, (void *)&nls, sizeof(struct sockaddr_nl))) {
+        close(fd);
+        return false;
+    }
+
+    self->fd = fd;
+    return true;
+}
+
+void hotplug_event_deinit(hotplug_event *self) {
+    if(self->fd > 0) {
+        close(self->fd);
+        self->fd = -1;
+    }
+}
+
+int hotplug_event_steal_fd(hotplug_event *self) {
+    const int fd = self->fd;
+    self->fd = -1;
+    return fd;
+}
+
+/* TODO: This assumes SUBSYSTEM= is output before DEVNAME=, is that always true? */
+static void hotplug_event_parse_netlink_data(hotplug_event *self, const char *line, hotplug_device_added_callback callback, void *userdata) {
+    const char *at_symbol = strchr(line, '@');
+    if(at_symbol) {
+        self->event_is_add = strncmp(line, "add@", 4) == 0;
+        self->subsystem_is_input = false;
+    } else if(self->event_is_add) {
+        if(strcmp(line, "SUBSYSTEM=input") == 0)
+            self->subsystem_is_input = true;
+
+        if(self->subsystem_is_input && strncmp(line, "DEVNAME=", 8) == 0)
+            callback(line+8, userdata);
+    }
+}
+
+/* Netlink uevent structure is documented here: https://web.archive.org/web/20160127215232/https://www.kernel.org/doc/pending/hotplug.txt */
+void hotplug_event_process_event_data(hotplug_event *self, int fd, hotplug_device_added_callback callback, void *userdata) {
+    const int bytes_read = read(fd, self->event_data, sizeof(self->event_data));
+    int data_index = 0;
+    if(bytes_read <= 0)
+        return;
+
+    /* Hotplug data ends with a newline and a null terminator */
+    while(data_index < bytes_read) {
+        hotplug_event_parse_netlink_data(self, self->event_data + data_index, callback, userdata);
+        data_index += strlen(self->event_data + data_index) + 1; /* Skip null terminator as well */
+    }
+}