Focus windows upon ConfigureWindow with stack-mode=Above (#2865)

fixes #2708
fixes #2745

src/handlers.c

@@ -400,11 +400,28 @@ static void handle_configure_request(xcb_configure_request_event_t *event) {
                 DLOG("Dock client will not be moved, we only support moving it to another output.\n");
             }
         }
+        fake_absolute_configure_notify(con);
+        return;
+    }
+
+    if (event->value_mask & XCB_CONFIG_WINDOW_STACK_MODE) {
+        DLOG("window 0x%08x wants to be stacked %d\n", event->window, event->stack_mode);
+        if (event->stack_mode == XCB_STACK_MODE_ABOVE) {
+            /* Emacs and IntelliJ Idea “request focus” by stacking their window
+             * above all others. */
+            if (!fullscreen && con_is_leaf(con)) {
+                if (strcmp(con_get_workspace(con)->name, "__i3_scratch") == 0) {
+                    DLOG("This is a scratchpad container, ignoring ConfigureRequest\n");
+                    return;
+                }
+
+                con_focus(con);
+                tree_render();
+            }
+        }
     }
 
     fake_absolute_configure_notify(con);
-
-    return;
 }
 
 /*