(mouse-drag-vertical-line-rightward-window): New function.

(mouse-drag-vertical-line): Call it.

1 files changed, 20 insertions, 1 deletions

diff --git a/lisp/mouse.el b/lisp/mouse.el
index c399515a3d2..145eb76446f 100644
--- a/lisp/mouse.el
+++ b/lisp/mouse.el
@@ -529,6 +529,24 @@ resized by dragging their header-line."
       (mouse-drag-mode-line-1 start-event nil))))
 
 
+(defun mouse-drag-vertical-line-rightward-window (window)
+  "Return a window that is immediately to the right of WINDOW, or nil."
+  (let ((bottom (nth 3 (window-inside-edges window)))
+        (left (nth 0 (window-inside-edges window)))
+        best best-right
+        (try (previous-window window)))
+    (while (not (eq try window))
+      (let ((try-top (nth 1 (window-inside-edges try)))
+            (try-bottom (nth 3 (window-inside-edges try)))
+            (try-right (nth 2 (window-inside-edges try))))
+        (if (and (< try-top bottom)
+                 (>= try-bottom bottom)
+                 (< try-right left)
+                 (or (null best-right) (> try-right best-right)))
+            (setq best-right try-right best try)))
+      (setq try (previous-window try)))
+    best))
+
 (defun mouse-drag-vertical-line (start-event)
   "Change the width of a window by dragging on the vertical line."
   (interactive "e")
@@ -594,7 +612,8 @@ resized by dragging their header-line."
                         ;; adjust the window on the left.
                         (if (eq which-side 'right)
                             (selected-window)
-                          (previous-window))))
+                          (mouse-drag-vertical-line-rightward-window
+                           (selected-window)))))
                    (setq x (- (car (cdr mouse))
                               (if (eq which-side 'right) 0 2))
                          edges (window-edges window)