Fix the asymmetry between posn-at-point and posn-at-x-y when header line is enabled

1 files changed, 32 insertions, 0 deletions

diff --git a/evil-common.el b/evil-common.el
index 5596d92..575f19f 100644
--- a/evil-common.el
+++ b/evil-common.el
@@ -871,6 +871,38 @@ Inhibits echo area messages, mode line updates and cursor changes."
   "Returns the number of currently visible lines."
   (- (window-height) 1))
 
+(defvar evil-cached-header-line-height nil
+  "Cached height of the header line.")
+
+(defun evil-header-line-height ()
+  "Return the height of the header line.
+If there is no header line, return nil."
+  (let ((posn (posn-at-x-y 0 0)))
+    (when (eq (posn-area posn) 'header-line)
+      (cdr (posn-object-width-height posn)))))
+
+(defun evil-posn-x-y (position)
+  "Return the x and y coordinates in POSITION.
+
+This function returns y offset from the top of the buffer area including
+the header line.  This definition could be changed in future.
+Note: On Emacs 22 and 23, y offset, returned by `posn-at-point' and taken
+by `posn-at-x-y', is relative to the top of the buffer area including
+the header line.
+However, on Emacs 24, y offset returned by `posn-at-point' is relative to
+the text area excluding the header line, while y offset taken by
+`posn-at-x-y' is relative to the buffer area including the header line.
+This asymmetry is by design according to GNU Emacs team.
+This function fixes the asymmetry between them on Emacs 24 and later versions.
+Borrowed from mozc.el."
+  (let ((xy (posn-x-y position)))
+    (when (and (> emacs-major-version 24) header-line-format)
+      (setcdr xy (+ (cdr xy)
+                    (or evil-cached-header-line-height
+                        (setq evil-cached-header-line-height (evil-header-line-height))
+                        0))))
+    xy))
+
 (defun evil-count-lines (beg end)
   "Return absolute line-number-difference betweeen `beg` and `end`.
 This should give the same results no matter where on the line `beg`