Cleanup and refactor x11 code

- Deleted X11 code for an unfinished/broken feature
- Rename xtra -> x11focus
- Cleanup the remaining code a bit

src/x11focus.c

@@ -0,0 +1,87 @@
+/*  x11focus.c
+ *
+ *
+ *  Copyright (C) 2020 Toxic All Rights Reserved.
+ *
+ *  This file is part of Toxic.
+ *
+ *  Toxic is free software: you can redistribute it and/or modify
+ *  it under the terms of the GNU General Public License as published by
+ *  the Free Software Foundation, either version 3 of the License, or
+ *  (at your option) any later version.
+ *
+ *  Toxic is distributed in the hope that it will be useful,
+ *  but WITHOUT ANY WARRANTY; without even the implied warranty of
+ *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ *  GNU General Public License for more details.
+ *
+ *  You should have received a copy of the GNU General Public License
+ *  along with Toxic.  If not, see <http://www.gnu.org/licenses/>.
+ *
+ */
+
+#include "x11focus.h"
+
+#ifndef __APPLE__
+
+#include <X11/Xlib.h>
+
+static struct Focus {
+    Display *display;
+    Window terminal_window;
+} Focus;
+
+static long unsigned int focused_window_id(void)
+{
+    if (!Focus.display) {
+        return 0;
+    }
+
+    Window focus;
+    int revert;
+
+    XLockDisplay(Focus.display);
+    XGetInputFocus(Focus.display, &focus, &revert);
+    XUnlockDisplay(Focus.display);
+
+    return focus;
+}
+
+bool is_focused(void)
+{
+    if (!Focus.display) {
+        return false;
+    }
+
+    return Focus.terminal_window == focused_window_id();
+}
+
+int init_x11focus(void)
+{
+    if (XInitThreads() == 0) {
+        return -1;
+    }
+
+    Focus.display = XOpenDisplay(NULL);
+
+    if (!Focus.display) {
+        return -1;
+    }
+
+    Focus.terminal_window = focused_window_id();
+
+    return 0;
+}
+
+void terminate_x11focus(void)
+{
+    if (!Focus.display || !Focus.terminal_window) {
+        return;
+    }
+
+    XLockDisplay(Focus.display);
+    XCloseDisplay(Focus.display);
+    XUnlockDisplay(Focus.display);
+}
+
+#endif /* !__APPLE__ */