Fix input focus transfer between workspaces

* exwm-input.el (exwm-input--set-focus): Make input focus revert to
parent by default (to prevent input focus from following pointer).

* exwm-input.el (exwm-input--update-focus): Switch to another workspace
if input focus is transfered to it.
* exwm-workspace.el (exwm-workspace--on-focus-in, exwm-workspace--init)
(exwm-workspace--exit): Remove `exwm-workspace--on-focus-in' and related
uses.

exwm-input.el

@@ -73,7 +73,7 @@ It's updated in several occasions, and only used by `exwm-input--set-focus'.")
         (exwm--log "Focus on #x%x with SetInputFocus" id)
         (xcb:+request exwm--connection
             (make-instance 'xcb:SetInputFocus
-                           :revert-to xcb:InputFocus:PointerRoot
+                           :revert-to xcb:InputFocus:Parent
                            :focus id
                            :time xcb:Time:CurrentTime)))
       (exwm-input--set-active-window id)
@@ -169,9 +169,15 @@ This value should always be overwritten.")
               (xcb:flush exwm--connection)))
         (when (eq (selected-window) window)
           (exwm--log "Focus on %s" window)
+          (if (and (exwm-workspace--workspace-p (selected-frame))
+                   (not (eq (selected-frame) exwm-workspace--current)))
+              ;; The focus is on another workspace (e.g. it got clicked)
+              ;; so switch to it.
+              (exwm-workspace-switch (selected-frame))
+            ;; The focus is still on the current workspace.
             (select-frame-set-input-focus (window-frame window) t)
             (exwm-input--set-active-window)
-          (xcb:flush exwm--connection)))))
+            (xcb:flush exwm--connection))))))
   (setq exwm-input--update-focus-lock nil))
 
 (defun exwm-input--on-minibuffer-setup ()

exwm-workspace.el

@@ -610,16 +610,6 @@ INDEX must not exceed the current number of workspaces."
          (exwm-workspace--workspace-from-frame-or-index frame-or-index)
        exwm-workspace--current))))
 
-(defun exwm-workspace--on-focus-in ()
-  "Handle unexpected frame switch."
-  ;; `focus-in-hook' is run by `handle-switch-frame'.
-  (unless (eq this-command #'handle-switch-frame)
-    (let ((index (exwm-workspace--position (selected-frame))))
-      (exwm--log "Focus on workspace %s" index)
-      (when (and index (/= index exwm-workspace-current-index))
-        (exwm--log "Workspace was switched unexpectedly")
-        (exwm-workspace-switch index)))))
-
 (defun exwm-workspace--set-desktop (id)
   "Set _NET_WM_DESKTOP for X window ID."
   (with-current-buffer (exwm--id->buffer id)
@@ -1374,8 +1364,6 @@ applied to all subsequently created X frames."
       ;; `minibuffer-completion-help') is not correct here.
       (cl-pushnew '(exwm-workspace--display-buffer) display-buffer-alist
                   :test #'equal))
-    ;; Handle unexpected frame switch.
-    (add-hook 'focus-in-hook #'exwm-workspace--on-focus-in)
     ;; Prevent `other-buffer' from selecting already displayed EXWM buffers.
     (modify-all-frames-parameters
      '((buffer-predicate . exwm-layout--other-buffer-predicate)))
@@ -1413,7 +1401,6 @@ applied to all subsequently created X frames."
   (setq display-buffer-alist
         (cl-delete '(exwm-workspace--display-buffer) display-buffer-alist
                    :test #'equal))
-  (remove-hook 'focus-in-hook #'exwm-workspace--on-focus-in)
   (advice-remove 'x-create-frame #'exwm-workspace--x-create-frame)
   (remove-hook 'after-make-frame-functions
                #'exwm-workspace--add-frame-as-workspace)