Do not set input focus in i3-input. (#2598)

This commit removes all traces of setting and reverting the input focus
in i3-input. We don't need to do this because grabbing the keyboard is
sufficient to have the attention we need.

Changing the input focus and reverting it can cause situations where i3
executes the IPC command before processing the FocusIn events. This leads
to i3's input focus change to be rejected due to the timing, leading to
an inconsistent focus state.

fixes #2597

i3-input/main.c

@@ -54,7 +54,6 @@ static int limit;
 xcb_window_t root;
 xcb_connection_t *conn;
 xcb_screen_t *root_screen;
-static xcb_get_input_focus_cookie_t focus_cookie;
 
 /*
  * Having verboselog(), errorlog() and debuglog() is necessary when using libi3.
@@ -79,24 +78,6 @@ void errorlog(char *fmt, ...) {
 void debuglog(char *fmt, ...) {
 }
 
-/*
- * Restores the X11 input focus to wherever it was before.
- * This is necessary because i3-input’s window has override_redirect=1
- * (→ unmanaged by the window manager) and thus i3-input changes focus itself.
- * This function is called on exit().
- *
- */
-static void restore_input_focus(void) {
-    xcb_generic_error_t *error;
-    xcb_get_input_focus_reply_t *reply = xcb_get_input_focus_reply(conn, focus_cookie, &error);
-    if (error != NULL) {
-        fprintf(stderr, "[i3-input] ERROR: Could not restore input focus (X error %d)\n", error->error_code);
-        return;
-    }
-    xcb_set_input_focus(conn, XCB_INPUT_FOCUS_POINTER_ROOT, reply->focus, XCB_CURRENT_TIME);
-    xcb_flush(conn);
-}
-
 /*
  * Concats the glyphs (either UCS-2 or UTF-8) to a single string, suitable for
  * rendering it (UCS-2) or sending it to i3 (UTF-8).
@@ -208,10 +189,6 @@ static void finish_input() {
     /* prefix the command if a prefix was specified on commandline */
     printf("command = %s\n", full);
 
-    restore_input_focus();
-
-    xcb_aux_sync(conn);
-
     ipc_send_message(sockfd, strlen(full), 0, (uint8_t *)full);
 
     free(full);
@@ -265,7 +242,6 @@ static int handle_key_press(void *ignored, xcb_connection_t *conn, xcb_key_press
         return 1;
     }
     if (sym == XK_Escape) {
-        restore_input_focus();
         exit(0);
     }
 
@@ -467,9 +443,6 @@ int main(int argc, char *argv[]) {
 
     sockfd = ipc_connect(socket_path);
 
-    /* Request the current InputFocus to restore when i3-input exits. */
-    focus_cookie = xcb_get_input_focus(conn);
-
     root_screen = xcb_aux_get_screen(conn, screen);
     root = root_screen->root;
 
@@ -509,10 +482,6 @@ int main(int argc, char *argv[]) {
     xcb_create_pixmap(conn, root_screen->root_depth, pixmap, win, logical_px(500), font.height + logical_px(8));
     xcb_create_gc(conn, pixmap_gc, pixmap, 0, 0);
 
-    /* Set input focus (we have override_redirect=1, so the wm will not do
-     * this for us) */
-    xcb_set_input_focus(conn, XCB_INPUT_FOCUS_POINTER_ROOT, win, XCB_CURRENT_TIME);
-
     /* Grab the keyboard to get all input */
     xcb_flush(conn);
 
@@ -531,7 +500,6 @@ int main(int argc, char *argv[]) {
 
     if (reply->status != XCB_GRAB_STATUS_SUCCESS) {
         fprintf(stderr, "Could not grab keyboard, status = %d\n", reply->status);
-        restore_input_focus();
         exit(-1);
     }