bug#34374: 27.0.50; Outside an eww buffer, optionally use new buffer when calling eww instead of reusing *eww*

[Göktuğ Kayaalp]

Eww should support conveniently avoiding using the same buffer even when
not in an eww buffer (M-x eww or browse-url).  Currently, in an eww
buffer, ‘eww-open-in-new-buffer’ opens the link under point in a new
buffer, and ‘eww’ reuses the buffer.  When running ‘eww’ outside an eww
buffer, it reuses the ‘*eww*’ buffer.  Attached is a patch where by
default this behaviour is retained, but when a new custom,
‘eww-reuse-buffer’ is truthy (defaults to nil), Eww uses a new buffer
(obtained via ‘generate-new-buffer’) instead, unless the current buffer
is an eww buffer.  The navigation behaviour in eww buffers is retained.

I have manually tested the general use of EWW with this patch applied.
But I haven’t found a test suite for EWW; if I missed it, I can run it,
or any other suggested testing.

In case the patch is good enough to apply as it is, I have my copyright
stuff sorted already.

All the best,
    -gk.


In GNU Emacs 27.0.50 (build 1, x86_64-pc-linux-gnu, X toolkit, Xaw3d scroll 
bars)
 of 2019-02-04 built on alpha
Repository revision: ef17247fe9cab2d59e470daad24314c868248b0a
Repository branch: master
Windowing system distributor 'The X.Org Foundation', version 11.0.12003000
System Description: Debian GNU/Linux buster/sid

Recent messages:
Mark set [3 times]
Mark saved where search started
Mark set
Auto-saving...done
eww-reuse-buffer
Quit [5 times]
eww-reuse-buffer
Saving file /home/g/co/External/emacs/lisp/net/eww.el...
Wrote /home/g/co/External/emacs/lisp/net/eww.el
Finding changes in /home/g/co/External/emacs/lisp/net/eww.el...done
Quit
Configured using:
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Load-path shadows:
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>From dd47aa509a7f7d7548e4c048e42e7dc32a12fbe9 Mon Sep 17 00:00:00 2001
From: =?UTF-8?q?=C4=B0=2E=20G=C3=B6ktu=C4=9F=20Kayaalp?= <self@gkayaalp.com>
Date: Thu, 7 Feb 2019 14:33:08 +0300
Subject: [PATCH] Support not reusing *eww* buffer when navigating from a
 non-eww one
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8
Content-Transfer-Encoding: 8bit

* lisp/net/eww.el (eww-reuse-buffer): New defcustom.
* lisp/net/eww.el (eww): Use the above to decide whether to use
‘get-buffer-create’ or ‘generate-new-buffer’.
* doc/misc/eww.texi (Basics):
* etc/NEWS: Document the new feature.
---
 doc/misc/eww.texi |  8 +++++++-
 etc/NEWS          |  6 ++++++
 lisp/net/eww.el   | 17 +++++++++++++++--
 3 files changed, 28 insertions(+), 3 deletions(-)

diff --git a/doc/misc/eww.texi b/doc/misc/eww.texi
index b299ea1fb7..cc96909ab3 100644
--- a/doc/misc/eww.texi
+++ b/doc/misc/eww.texi
@@ -98,10 +98,16 @@ Basics
 (@code{eww-copy-page-url}) will copy the current URL to the kill ring.
 
 @findex eww-open-in-new-buffer
+@vindex eww-reuse-buffer
 @kindex M-RET
   The @kbd{M-@key{RET}} command (@code{eww-open-in-new-buffer}) opens the
 URL at point in a new EWW buffer, akin to opening a link in a new
-``tab'' in other browsers.
+``tab'' in other browsers.  If you want this same behavior when
+following links or running @code{eww} in a buffer that is not in
+@code{eww-mode}, set @code{eww-reuse-buffer} to @code{nil}.  Normal
+navigation within an @code{eww-mode} buffer will not be affected, but
+running @kbd{M-x eww} or following a URI with @code{browse-url} family
+of functions will result in new eww buffers.
 
 @findex eww-readable
 @kindex R
diff --git a/etc/NEWS b/etc/NEWS
index 72a6b385a8..5dc4c8b8b2 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -652,6 +652,12 @@ has been executed.
 If set, shr will not render tags with attribute 'aria-hidden="true"'.
 This attribute is meant to tell screen readers to ignore a tag.
 
++++
+*** New option 'eww-reuse-buffer'.
+If set (default), eww will reuse the "*eww*" buffer when called from a
+non-eww buffer.  If not, it will generate a new buffer and use it
+instead.
+
 ** Htmlfontify
 
 *** The functions 'hfy-color', 'hfy-color-vals' and
diff --git a/lisp/net/eww.el b/lisp/net/eww.el
index 3b7d9d5c2f..2ac4c606de 100644
--- a/lisp/net/eww.el
+++ b/lisp/net/eww.el
@@ -153,6 +153,12 @@ eww-form-checkbox-symbol
                  (const "☐")            ; Unicode BALLOT BOX
                  string))
 
+(defcustom eww-reuse-buffer t
+  "Reuse the *eww* buffer when not in an `eww-mode' buffer."
+  :version "27.1"
+  :group 'eww
+  :type 'boolean)
+
 (defface eww-form-submit
   '((((type x w32 ns) (class color))   ; Like default mode line
      :box (:line-width 2 :style released-button)
@@ -250,7 +256,12 @@ eww-suggested-uris
 (defun eww (url)
   "Fetch URL and render the page.
 If the input doesn't look like an URL or a domain name, the
-word(s) will be searched for via `eww-search-prefix'."
+word(s) will be searched for via `eww-search-prefix'.
+
+When the current buffer is not in `eww-mode', if
+`eww-reuse-buffer' is non-nil, the *eww* buffer will be reused if
+available, otherwise generated; if set to nil instead, a new
+buffer will be used in case *eww* is already in use."
   (interactive
    (let* ((uris (eww-suggested-uris))
          (prompt (concat "Enter URL or keywords"
@@ -261,7 +272,9 @@ eww
   (pop-to-buffer-same-window
    (if (eq major-mode 'eww-mode)
        (current-buffer)
-     (get-buffer-create "*eww*")))
+     (funcall
+      (if eww-reuse-buffer #'get-buffer-create #'generate-new-buffer)
+      "*eww*")))
   (eww-setup-buffer)
   ;; Check whether the domain only uses "Highly Restricted" Unicode
   ;; IDNA characters.  If not, transform to punycode to indicate that
-- 
2.20.1