Center floating windows by default

This commit makes a floating window centered to its leading window if it has
a valid WM_TRANSIENT_FOR property set. Other it's placed at the center of the
screen.

exwm-floating.el

@@ -67,6 +67,7 @@
          (y (slot-value exwm--geometry 'y))
          (width (slot-value exwm--geometry 'width))
          (height (slot-value exwm--geometry 'height)))
+    (exwm--log "Floating geometry (original): %dx%d%+d%+d" width height x y)
     ;; Save window IDs
     (set-frame-parameter frame 'exwm-window-id frame-id)
     (set-frame-parameter frame 'exwm-outer-id outer-id)
@@ -102,7 +103,24 @@
         (when (= 0 height) (setq height (/ display-height 2)))
         ;; Completely outside
         (when (or (> y display-height) (> 0 (+ y display-height)))
-          (setq y (/ (- display-height height) 2)))))
+          (setq y (/ (- display-height height) 2))))
+      ;; Center floating windows
+      (when (and (= x 0) (= y 0))
+        (let ((buffer (exwm--id->buffer exwm-transient-for))
+              window edges)
+          (when (and buffer (setq window (get-buffer-window buffer)))
+            (setq edges (window-inside-absolute-pixel-edges window))
+            (unless (and (<= width (- (elt edges 2) (elt edges 0)))
+                         (<= height (- (elt edges 3) (elt edges 1))))
+              (setq edges nil)))
+          (if edges
+              ;; Put at the center of leading window
+              (setq x (/ (- (+ (elt edges 2) (elt edges 0)) width) 2)
+                    y (/ (- (+ (elt edges 3) (elt edges 1)) height) 2))
+            ;; Put at the center of screen
+            (setq x (/ (- display-width width) 2)
+                  y (/ (- display-height height) 2))))))
+    (exwm--log "Floating geometry (corrected): %dx%d%+d%+d" width height x y)
     ;; Set OverrideRedirect on this frame
     (xcb:+request exwm--connection
         (make-instance 'xcb:ChangeWindowAttributes

exwm-input.el

@@ -86,7 +86,6 @@ It's updated in several occasions, and only used by `exwm-input--set-focus'.")
   "Update input focus."
   (when (and (frame-parameter nil 'exwm-window-id) ;e.g. emacsclient frame
              (eq (current-buffer) (window-buffer))) ;e.g. `with-temp-buffer'
-    (exwm--log "EXWM-INPUT--UPDATE-FOCUS")
     (if (eq major-mode 'exwm-mode)
         (progn (exwm--log "Set focus ID to #x%x" exwm--id)
                (setq exwm-input--focus-id exwm--id)

exwm-manage.el

@@ -276,6 +276,8 @@ corresponding buffer.")
         buffer edges)
     (xcb:unmarshal obj data)
     (with-slots (window x y width height border-width) obj
+      (exwm--log "ConfigureRequest from #x%x @%dx%d%+d%+d, border: %d"
+                 window width height x y border-width)
       (if (setq buffer (exwm--id->buffer window))
           ;; Send client message for managed windows
           (with-current-buffer buffer
@@ -286,6 +288,7 @@ corresponding buffer.")
                     (or exwm--floating-edges
                         (window-inside-absolute-pixel-edges
                          (get-buffer-window)))))
+            (exwm--log "Reply with ConfigureNotify (edges): %s" edges)
             (xcb:+request exwm--connection
                 (make-instance 'xcb:SendEvent
                                :propagate 0 :destination window
@@ -300,6 +303,7 @@ corresponding buffer.")
                                         :height (- (elt edges 3) (elt edges 1))
                                         :border-width 0 :override-redirect 0)
                                        exwm--connection))))
+        (exwm--log "ConfigureWindow (preserve geometry)")
         ;; Configure unmanaged windows
         (xcb:+request exwm--connection
             (make-instance 'xcb:ConfigureWindow
@@ -317,6 +321,7 @@ corresponding buffer.")
   "Handle MapRequest event."
   (let ((obj (make-instance 'xcb:MapRequest)))
     (xcb:unmarshal obj data)
+    (exwm--log "MapRequest from #x%x" (slot-value obj 'window))
     (exwm-manage--manage-window (slot-value obj 'window))))
 
 (defun exwm-manage--on-UnmapNotify (data synthetic)
@@ -324,6 +329,7 @@ corresponding buffer.")
   (unless synthetic
     (let ((obj (make-instance 'xcb:UnmapNotify)))
       (xcb:unmarshal obj data)
+      (exwm--log "UnmapNotify from #x%x" (slot-value obj 'window))
       (exwm-manage--unmanage-window (slot-value obj 'window) t))))
 
 (defun exwm-manage--on-DestroyNotify (data synthetic)
@@ -331,6 +337,7 @@ corresponding buffer.")
   (unless synthetic
     (let ((obj (make-instance 'xcb:DestroyNotify)))
       (xcb:unmarshal obj data)
+      (exwm--log "DestroyNotify from #x%x" (slot-value obj 'window))
       (exwm-manage--unmanage-window (slot-value obj 'window)))))
 
 (defun exwm-manage--init ()