Subject: bug#28814: closed (Re: bug#28814: [BUMP, PATCH] (26.0.90; When *xref* window is needed, original window-switching intent is lost ))

From: [email-masked] (GNU bug Tracking System)
Date: Fri, 03 Nov 2017 16:19:02 +0000

Your bug report

#28814: 26.0.90; When *xref* window is needed, original window-switching intent is lost 

which was filed against the emacs package, has been closed.

The explanation is attached below, along with your original report.
If you require more details, please reply to [email-masked].

-- 
28814: http://debbugs.gnu.org/cgi/bugreport.cgi?bug=28814
GNU Bug Tracking System
Contact [email-masked] with problems

Subject: Re: bug#28814: [BUMP, PATCH] (26.0.90; When *xref* window is needed, original window-switching intent is lost )
From: [email-masked] (João Távora)
To: Eli Zaretskii <[email-masked]>
Cc: [email-masked], [email-masked], [email-masked]
Date: Fri, 03 Nov 2017 16:18:13 +0000
List-Id: <debbugs-submit.debbugs.gnu.org>

Eli Zaretskii <[email-masked]> writes:

>> From: [email-masked] (João Távora)
>> Cc: [email-masked],  [email-masked]
>> Date: Sat, 28 Oct 2017 20:19:00 +0100
>> 
>> I hope I fixed everything in these patches.
>
> Thanks, let's get this into the emacs-26 branch, after fixing the
> gotchas below.

Done.  Pushed 3 commits to emacs-26.

>> +buffers, quits the window before jumping to the destination. In many
>                                                               ^^
> Two spaces between sentences, please.

Sigh. This is the hardest for me to remember.  Are there any tools to
help with this?

João

Subject: 26.0.90; When *xref* window is needed, original window-switching intent is lost
From: [email-masked] (João Távora)
To: [email-masked], [email-masked]
Date: Fri, 13 Oct 2017 17:07:36 +0100
List-Id: <debbugs-submit.debbugs.gnu.org>

Hi Dmitry, maintainters,

Here are two patches to fix what I believe is a small but annoying bug
in xref.el.

I'll try to explain as clearly as possible: As you know, if the user
presses 'M-.' in a single-ref definition, he/she is transported to a new
buffer.

But there are other situations: when xref-find-definitions finds more
than one definition, a list is shown in an *xref* buffer, normally in a
new window. When the user selects an "xref" with xref-goto-xref, a
buffer and window switch happen.  Anyway, so far so good.

The problem is there is also 'C-x 4 .' and 'C-x 5 .' for
xref-find-definitions-other-window and xref-find-definitions-other-frame
respectively. These work just fine when an *xref* buffer isn't needed,
but when it is, the original intent of using another window or frame
will be lost when the user eventually selects a definition.

It shouldn't be so, in my opinion.

The first patch I attach (0001-Honor-window....patch) fixes this bug. I
hope it is readable enough but I can explain how it works in detail.

I also attach a second patch (0002-Quit-the....patch), that does not
really fix a bug, but changes the behavior of xref-goto-xref to
something much nicer: it quits the *xref* window before going to the
reference.

This brings a nice result: As always 'M-.' switches buffers if there is
only one definition.  Now, if there is more than one, the final state
after selecting one of these definitions is the same as if there had
only been one in the first place.  I think this makes sense because it
preserves the expectations of the user who probably wants M-. to behave
as predictably as possible.

Here's hoping you're not really confused by this report,
João

>From 1cba860d6a2c45e0fa690065b2bf4e6658e87628 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20T=C3=A1vora?= <[email-masked]>
Date: Fri, 13 Oct 2017 15:13:14 +0100
Subject: [PATCH 1/2] Honor window-switching intents in xref-find-definitions

When there is more than one xref to jump to, and an *xref* window
appears to help the user choose, the original intent to open a
definition another window or frame is remembered when the choice to go
to or show a reference is finally made.

* lisp/progmodes/xref.el (xref--show-pos-in-buf): Rewrite.
(xref--original-window-intent): New variable.
(xref--original-window): Rename from xref--window and move up
here for clarity.
(xref--show-pos-in-buf): Rewrite.  Don't take SELECT arg here.
(xref--show-location): Handle window selection decision here.
(xref--window): Rename to xref--original-window.
(xref-show-location-at-point): Don't attempt window management here.
(xref--show-xrefs): Ensure display-action intent is saved.
---
 lisp/progmodes/xref.el | 73 +++++++++++++++++++++++++++++++++++---------------
 1 file changed, 52 insertions(+), 21 deletions(-)

diff --git a/lisp/progmodes/xref.el b/lisp/progmodes/xref.el
index 80cdcb3f18..768fa15a6b 100644
--- a/lisp/progmodes/xref.el
+++ b/lisp/progmodes/xref.el
@@ -449,43 +449,72 @@ xref--with-dedicated-window
        (when xref-w
          (set-window-dedicated-p xref-w xref-w-dedicated)))))
 
-(defun xref--show-pos-in-buf (pos buf select)
-  (let ((xref-buf (current-buffer))
-        win)
+(defvar-local xref--original-window-intent nil
+  "Original window-switching intent before xref buffer creation.")
+
+(defvar-local xref--original-window nil
+  "The original window this xref buffer was created from.")
+
+(defun xref--show-pos-in-buf (pos buf)
+  "Goto and display position POS of buffer BUF in a window.
+Honour `xref--original-window-intent', run `xref-after-jump-hook'
+and finally return the window."
+  (let* ((xref-buf (current-buffer))
+         (pop-up-frames
+          (or (eq xref--original-window-intent 'frame)
+              pop-up-frames))
+         (action
+          (cond ((memq
+                  xref--original-window-intent
+                  '(window frame))
+                 t)
+                ((and
+                  (window-live-p xref--original-window)
+                  (or (not (window-dedicated-p xref--original-window))
+                      (eq (window-buffer xref--original-window) buf)))
+                 `(,(lambda (buf _alist)
+                      (set-window-buffer xref--original-window buf)
+                      xref--original-window))))))
     (with-selected-window
-        (xref--with-dedicated-window
-         (display-buffer buf))
+        (with-selected-window
+            ;; Just before `display-buffer', place ourselves in the
+            ;; original window to suggest preserving it. Of course, if
+            ;; user has deleted the original window, all bets are off,
+            ;; just use the selected one.
+            (or (and (window-live-p xref--original-window)
+                     xref--original-window)
+                (selected-window))
+          (display-buffer buf action))
       (xref--goto-char pos)
       (run-hooks 'xref-after-jump-hook)
       (let ((buf (current-buffer)))
-        (setq win (selected-window))
         (with-current-buffer xref-buf
-          (setq-local other-window-scroll-buffer buf))))
-    (when select
-      (select-window win))))
+          (setq-local other-window-scroll-buffer buf)))
+      (selected-window))))
 
 (defun xref--show-location (location &optional select)
   (condition-case err
       (let* ((marker (xref-location-marker location))
              (buf (marker-buffer marker)))
-        (xref--show-pos-in-buf marker buf select))
+        (cond (select
+               (select-window (xref--show-pos-in-buf marker buf)))
+              (t
+               (save-selected-window
+                 (xref--with-dedicated-window
+                  (let (;; save-selected-window doesn't resist frame
+                        ;; raises
+                        (display-buffer-overriding-action
+                         '(nil . ((inhibit-switch-frame . t)))))
+                    (xref--show-pos-in-buf marker buf)))))))
     (user-error (message (error-message-string err)))))
 
-(defvar-local xref--window nil
-  "The original window this xref buffer was created from.")
-
 (defun xref-show-location-at-point ()
   "Display the source of xref at point in the appropriate window, if any."
   (interactive)
   (let* ((xref (xref--item-at-point))
          (xref--current-item xref))
     (when xref
-      ;; Try to avoid the window the current xref buffer was
-      ;; originally created from.
-      (if (window-live-p xref--window)
-          (with-selected-window xref--window
-            (xref--show-location (xref-item-location xref)))
-        (xref--show-location (xref-item-location xref))))))
+      (xref--show-location (xref-item-location xref)))))
 
 (defun xref-next-line ()
   "Move to the next xref and display its source in the appropriate window."
@@ -727,7 +756,8 @@ xref--show-xref-buffer
         (xref--xref-buffer-mode)
         (pop-to-buffer (current-buffer))
         (goto-char (point-min))
-        (setq xref--window (assoc-default 'window alist))
+        (setq xref--original-window (assoc-default 'window alist)
+              xref--original-window-intent (assoc-default 'display-action alist))
         (current-buffer)))))
 
 
@@ -754,7 +784,8 @@ xref--show-xrefs
    (t
     (xref-push-marker-stack)
     (funcall xref-show-xrefs-function xrefs
-             `((window . ,(selected-window)))))))
+             `((window . ,(selected-window))
+               (display-action . ,display-action))))))
 
 (defun xref--prompt-p (command)
   (or (eq xref-prompt-for-identifier t)
-- 
2.11.0

>From 228cb812197bd68b2fb6eccc60d7956675a728f3 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?Jo=C3=A3o=20T=C3=A1vora?= <[email-masked]>
Date: Fri, 13 Oct 2017 16:37:47 +0100
Subject: [PATCH 2/2] Quit the *xref* window if user decides to go to a ref

* lisp/progmodes/xref.el (xref--show-location): When SELECT is
t, quit window.
---
 lisp/progmodes/xref.el | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/lisp/progmodes/xref.el b/lisp/progmodes/xref.el
index 768fa15a6b..3a5e9e53ed 100644
--- a/lisp/progmodes/xref.el
+++ b/lisp/progmodes/xref.el
@@ -495,9 +495,12 @@ xref--show-pos-in-buf
 (defun xref--show-location (location &optional select)
   (condition-case err
       (let* ((marker (xref-location-marker location))
-             (buf (marker-buffer marker)))
+             (buf (marker-buffer marker))
+             (xref-buffer (current-buffer)))
         (cond (select
-               (select-window (xref--show-pos-in-buf marker buf)))
+               (quit-window nil nil)
+               (with-current-buffer xref-buffer
+                 (select-window (xref--show-pos-in-buf marker buf))))
               (t
                (save-selected-window
                  (xref--with-dedicated-window
-- 
2.11.0