Subject: Re: bug#17768: 24.3; problem with two ruler-mode windows

From: Andrea Rossetti <[email-masked]>
Date: Sat, 14 Jun 2014 19:22:21 +0200

martin rudalics <[email-masked]> writes:
> Could you try testing it
> with three and more side-by-side windows and all sorts of clicks ruler
> mode can handle and possibly post a corresponding patch?
>

Hi, here's my tentative patches. I checked out from
http://git.savannah.gnu.org/cgit/emacs.git, last
commit was 6449128a5ab4a47a281de6117b86661dcc05b599, and
made two patches.

  First patch applies the changes that we supposed could
solve the problem of the wrong offset.

>From 88a4f9fb9d2eace74a737205a26b26f35cb21cf6 Mon Sep 17 00:00:00 2001
From: Andrea Rossetti <[email-masked]>
Date: Sat, 14 Jun 2014 17:26:49 +0200
Subject: [PATCH 1/2] lisp/ruler-mode.el: correct offset of "set margin" and
 "drag column" mouse operations

---
 lisp/ruler-mode.el | 5 ++---
 1 file changed, 2 insertions(+), 3 deletions(-)

diff --git a/lisp/ruler-mode.el b/lisp/ruler-mode.el
index 9e32a2f..238754e 100644
--- a/lisp/ruler-mode.el
+++ b/lisp/ruler-mode.el
@@ -306,7 +306,6 @@ or remove a tab stop.  \\[ruler-mode-toggle-show-tab-stops] or
   "Return a column number relative to the selected window.
 N is a column number relative to selected frame."
   (- n
-     (car (window-edges))
      (or (car (window-margins)) 0)
      (fringe-columns 'left)
      (scroll-bar-columns 'left)))
@@ -321,7 +320,7 @@ START-EVENT is the mouse click event."
     (when (eq start end) ;; mouse click
       (save-selected-window
         (select-window (posn-window start))
-        (setq col (- (car (posn-col-row start)) (car (window-edges))
+        (setq col (- (car (posn-col-row start))
                      (scroll-bar-columns 'left))
               w   (- (ruler-mode-full-window-width)
                      (scroll-bar-columns 'left)
@@ -343,7 +342,7 @@ START-EVENT is the mouse click event."
     (when (eq start end) ;; mouse click
       (save-selected-window
         (select-window (posn-window start))
-        (setq col (- (car (posn-col-row start)) (car (window-edges))
+        (setq col (- (car (posn-col-row start))
                      (scroll-bar-columns 'left))
               w   (- (ruler-mode-full-window-width)
                      (scroll-bar-columns 'left)
-- 
1.8.1.msysgit.1

 I tested patch1 somewhat randomly, opening 4/5 windows horizontally,
1/2 windows vertically, and did also some attempt splitting windows
in two frames. Played also a bit on the text-only Emacs (using MSYS shell).

  Everything worked fine with patch1, except for an unexpected small
and non-blocking issue (let's call it "diagonal-drag" issue) that
can be reproduced as follows:

- C-x 3 M-x ruler-mode (you should see two windows with ruler)
- click S-<mouse-1> on the ruler of the rightmost window, this will set
  a left margin, choose a width of around 10~20 chars
- drag "diagonally" a column, for example moving down-left the
  fill-column, until the cursor goes a few pixels below the ruler area
- you will see that the dragged column will "jump" innaturally to the
  left of around 10~20 chars

  Tentative diagnosys: function `ruler-mode-window-col' returns a
different column value depending if you are inside or outside the 
ruler area. The actual problem is probably inherited from `posn-col-row',
but I could not clarify any better.

  I wrote patch 2, that worked for me to solve the "diagonal-drag" issue.

>From e521c93c296377d1733e8801832f3066e4cc4ede Mon Sep 17 00:00:00 2001
From: Andrea Rossetti <[email-masked]>
Date: Sat, 14 Jun 2014 17:32:03 +0200
Subject: [PATCH 2/2] lisp/ruler-mode.el: fix offset for mouse dragging beyond
 header line

---
 lisp/ruler-mode.el | 23 ++++++++++++++---------
 1 file changed, 14 insertions(+), 9 deletions(-)

diff --git a/lisp/ruler-mode.el b/lisp/ruler-mode.el
index 238754e..097a13e 100644
--- a/lisp/ruler-mode.el
+++ b/lisp/ruler-mode.el
@@ -302,12 +302,17 @@ or remove a tab stop.  \\[ruler-mode-toggle-show-tab-stops] or
   (let ((edges (window-edges)))
     (- (nth 2 edges) (nth 0 edges))))
 
-(defsubst ruler-mode-window-col (n)
+(defsubst ruler-mode-window-col (start-or-end-event)
   "Return a column number relative to the selected window.
-N is a column number relative to selected frame."
-  (- n
-     (or (car (window-margins)) 0)
-     (fringe-columns 'left)
+START-OR-END-EVENT is the start point or end point
+of a mouse click or mouse drag event.
+
+See also: `event-start', `event-end', `posn-col-row', `posn-area'.
+"
+  (- (car (posn-col-row start-or-end-event))
+     (if (eq (posn-area start) 'header-line)
+         (+ (or (car (window-margins)) 0) (fringe-columns 'left))
+       0)
      (scroll-bar-columns 'left)))
 
 (defun ruler-mode-mouse-set-left-margin (start-event)
@@ -371,7 +376,7 @@ dragging.  See also the variable `ruler-mode-dragged-symbol'."
          col newc oldc)
     (save-selected-window
       (select-window (posn-window start))
-      (setq col  (ruler-mode-window-col (car (posn-col-row start)))
+      (setq col  (ruler-mode-window-col start)
             newc (+ col (window-hscroll)))
       (and
        (>= col 0) (< col (window-width))
@@ -454,7 +459,7 @@ Called on each mouse motion event START-EVENT."
          col newc)
     (save-selected-window
       (select-window (posn-window start))
-      (setq col  (ruler-mode-window-col (car (posn-col-row end)))
+      (setq col  (ruler-mode-window-col end)
             newc (+ col (window-hscroll)))
       (when (and (>= col 0) (< col (window-width)))
         (set ruler-mode-dragged-symbol newc)))))
@@ -470,7 +475,7 @@ START-EVENT is the mouse click event."
       (when (eq start end) ;; mouse click
         (save-selected-window
           (select-window (posn-window start))
-          (setq col (ruler-mode-window-col (car (posn-col-row start)))
+          (setq col (ruler-mode-window-col start)
                 ts  (+ col (window-hscroll)))
           (and (>= col 0) (< col (window-width))
                (not (member ts tab-stop-list))
@@ -490,7 +495,7 @@ START-EVENT is the mouse click event."
       (when (eq start end) ;; mouse click
         (save-selected-window
           (select-window (posn-window start))
-          (setq col (ruler-mode-window-col (car (posn-col-row start)))
+          (setq col (ruler-mode-window-col start)
                 ts  (+ col (window-hscroll)))
           (and (>= col 0) (< col (window-width))
                (member ts tab-stop-list)
-- 
1.8.1.msysgit.1

  And finally: I noticed another independent bug ("text-scale issue"),
i.e. most ruler's mouse operation have wrong offset if you adjust
text scale (C-x C-+).

  If anyone reading is interested to help, here's a proposed action plan:

- may you please try to play with patch1, and give advice if it could be
  acceptable for a commit 

- I guess that patch2 is unacceptable (BTW it changes the definition of
  ruler-mode-window-col, I assumed that ruler-mode.el is the only
  program calling it) but it's the best I could squeeze out of my head...
  any help or constructive criticism is welcome :)

- be aware of the "text-scale" issue but don't test for it; it seems
  a totally independent issue so I'd rather send another bug report for it

  Thanks for your attention, kindest regards.

  Andrea