Fix mouse-dragging mode lines on text-mode terminals.

 lisp/mouse.el (mouse-drag-line): On text-mode frames, count the mode
 line and header line as 1 pixel.  This fixes the 1-"pixel" (row)
 discrepancy between window-pixel-edges and mouse events, and
 avoids moving mode line up when the mouse click is on the modeline
 and no drag is attempted.

2 files changed, 23 insertions, 2 deletions

diff --git a/lisp/ChangeLog b/lisp/ChangeLog
index 2bd234e12e0..9f31741a1c5 100644
--- a/lisp/ChangeLog
+++ b/lisp/ChangeLog
@@ -1,3 +1,11 @@
+2014-09-09  Eli Zaretskii  <eliz@gnu.org>
+
+        * mouse.el (mouse-drag-line): On text-mode frames, count the mode
+        line and header line as 1 pixel.  This fixes the 1-"pixel" (row)
+        discrepancy between window-pixel-edges and mouse events, and
+        avoids moving mode line up when the mouse click is on the modeline
+        and no drag is attempted.
+
 2014-09-08  Glenn Morris  <rgm@gnu.org>
 
         * calendar/calendar.el (calendar-basic-setup):
diff --git a/lisp/mouse.el b/lisp/mouse.el
index 99407d9f9cf..d84c6c119ed 100644
--- a/lisp/mouse.el
+++ b/lisp/mouse.el
@@ -395,7 +395,16 @@ must be one of the symbols `header', `mode', or `vertical'."
       ;; Check whether header-line can be dragged at all.
       (if (window-at-side-p window 'top)
           (setq draggable nil)
-        (setq height (/ (window-header-line-height window) 2))
+        ;; window-pixel-edges includes the header and mode lines, so
+        ;; we need to account for that when calculating window growth.
+        ;; On GUI frames, assume the mouse is approximately in the
+        ;; middle of the header/mode line, so we need only half the
+        ;; height in pixels.
+        (setq height
+              (cond
+               ((display-graphic-p frame)
+                (/ (window-header-line-height window) 2))
+               (t  (window-header-line-height window))))
         (setq window (window-in-direction 'above window t))))
      ((eq line 'mode)
       ;; Check whether mode-line can be dragged at all.
@@ -410,7 +419,11 @@ must be one of the symbols `header', `mode', or `vertical'."
                              (eq minibuffer-window
                                  (active-minibuffer-window))))))
           (setq draggable nil)
-        (setq height (/ (window-mode-line-height window) 2))))
+        (setq height
+              (cond
+               ((display-graphic-p frame)
+                (/ (window-mode-line-height window) 2))
+               (t  (window-mode-line-height window))))))
      ((eq line 'vertical)
       ;; Get the window to adjust for the vertical case.  If the scroll
       ;; bar is on the window's right or we drag a vertical divider,