Fix sticky focus when switching to workspace on different output

See the testcase for the exact steps to reproduce the problem.

src/workspace.c

@@ -410,7 +410,6 @@ static void workspace_defer_update_urgent_hint_cb(EV_P_ ev_timer *w, int revents
  */
 void workspace_show(Con *workspace) {
     Con *current, *old = NULL;
-    Con *old_focus = focused;
 
     /* safe-guard against showing i3-internal workspaces like __i3_scratch */
     if (con_is_internal(workspace))
@@ -433,6 +432,13 @@ void workspace_show(Con *workspace) {
         return;
     }
 
+    /* Used to correctly update focus when pushing sticky windows. Holds the
+     * previously focused container in the same output as workspace. For
+     * example, if a sticky window is focused and then we switch focus to a
+     * workspace in another output and then switch to a third workspace in the
+     * first output, the sticky window needs to be refocused. */
+    Con *old_focus = old ? con_descend_focused(old) : NULL;
+
     /* Remember currently focused workspace for switching back to it later with
      * the 'workspace back_and_forth' command.
      * NOTE: We have to duplicate the name as the original will be freed when

testcases/t/285-sticky.t

@@ -16,7 +16,14 @@
 #
 # Tests sticky windows.
 # Ticket: #1455
-use i3test;
+use i3test i3_config => <<EOT;
+# i3 config file (v4)
+font -misc-fixed-medium-r-normal--13-120-75-75-C-70-iso10646-1
+
+workspace ws-on-0 output fake-0
+
+fake-outputs 1024x768+0+0,1024x768+1024+0
+EOT
 
 my ($ws, $tmp, $focused);
 
@@ -108,6 +115,24 @@ cmd '[con_mark=sticky] sticky enable';
 is(@{get_ws($ws)->{floating_nodes}}, 1, 'the sticky window jumps to the front');
 kill_all_windows;
 
+###############################################################################
+# 7: Given a sticky floating container and a workspace on another output, when
+#    a new workspace assigned to the first output is focused, then the sticky
+#    container should jump to the new workspace and have input focus correctly.
+###############################################################################
+$ws = fresh_workspace(output => 0);
+open_floating_window;
+cmd 'sticky enabled';
+$focused = get_focused($ws);
+$ws = fresh_workspace(output => 1);
+
+is(@{get_ws($ws)->{floating_nodes}}, 0, 'the sticky window didn\'t jump to a workspace on a different output');
+$ws = 'ws-on-0';
+cmd "workspace $ws";
+is(@{get_ws($ws)->{floating_nodes}}, 1, 'the sticky window moved to new workspace on first output');
+is(get_focused($ws), $focused, 'the sticky window has focus');
+kill_all_windows;
+
 ###############################################################################
 
 done_testing;