bug#72241: 31.0.50; [PATCH] Use a dedicated buffer for `doc-view-open-text'

bug#72241: 31.0.50; [PATCH] Use a dedicated buffer for `doc-view-open-text'

[Manuel Giraud via Bug reports for GNU Emacs, the Swiss army knife of text editors]

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Hi,

Here is a patch for DocView that makes it use a dedicated buffer for the
text representation of a document.  This is what was suggested by Stefan
M. in a comment (circa 2019).


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From 03d83f95c9a6502bf6b85d0b14e47022cf29bd3d Mon Sep 17 00:00:00 2001
From: Manuel Giraud <manuel@ledu-giraud.fr>
Date: Sun, 21 Jul 2024 18:52:52 +0200
Subject: [PATCH] Use a dedicated buffer for `doc-view-open-text'

* lisp/doc-view.el (doc-view-open-text): Create a new "doc's
contents" buffer an switch to it.
(doc-view-toggle-display): Switch back to the document buffer and
kill the "doc's contents" one.
---
 lisp/doc-view.el | 60 +++++++++++++++++++-----------------------------
 1 file changed, 24 insertions(+), 36 deletions(-)

diff --git a/lisp/doc-view.el b/lisp/doc-view.el
index 801783bd766..6313ee83857 100644
--- a/lisp/doc-view.el
+++ b/lisp/doc-view.el
@@ -1768,34 +1768,25 @@ doc-view-open-text
     (let ((txt (expand-file-name "doc.txt" (doc-view--current-cache-dir)))
           (page (doc-view-current-page)))
       (if (file-readable-p txt)
-	  (let ((inhibit-read-only t)
-		(buffer-undo-list t)
-		(dv-bfn doc-view--buffer-file-name))
-	    (erase-buffer)
-            ;; FIXME: Replacing the buffer's PDF content with its txt rendering
-            ;; is pretty risky.  We should probably use *another*
-            ;; buffer instead, so there's much less risk of
-            ;; overwriting the PDF file with some text rendering.
-	    (set-buffer-multibyte t)
-	    (insert-file-contents txt)
-	    (doc-view--text-view-mode)
-	    (setq-local doc-view--buffer-file-name dv-bfn)
-	    (set-buffer-modified-p nil)
-	    (doc-view-minor-mode)
-            (goto-char (point-min))
-            ;; Put point at the start of the page the user was
-            ;; reading.  Pages are separated by Control-L characters.
-            (re-search-forward page-delimiter nil t (1- page))
-	    (add-hook 'write-file-functions
-		      (lambda ()
-                        ;; FIXME: If the user changes major mode and then
-                        ;; saves the buffer, the PDF file will be clobbered
-                        ;; with its txt rendering!
-			(when (eq major-mode 'doc-view--text-view-mode)
-			  (error "Cannot save text contents of document %s"
-				 buffer-file-name)))
-		      nil t))
-	(doc-view-doc->txt txt 'doc-view-open-text)))))
+          (let ((dv-bfn doc-view--buffer-file-name)
+                (dv-text-buffer-name (format "%s/text" (buffer-name))))
+            ;; Prepare the text buffer
+            (with-current-buffer (get-buffer-create dv-text-buffer-name)
+              (let ((inhibit-read-only t)
+                    (buffer-undo-list t))
+                (erase-buffer)
+                (set-buffer-multibyte t)
+                (insert-file-contents txt)
+                (doc-view--text-view-mode)
+                (setq-local doc-view--buffer-file-name dv-bfn)
+                (set-buffer-modified-p nil)
+                (doc-view-minor-mode)
+                (goto-char (point-min))
+                ;; Put point at the start of the page the user was
+                ;; reading.  Pages are separated by Control-L characters.
+                (re-search-forward page-delimiter nil t (1- page))))
+            (switch-to-buffer (get-buffer dv-text-buffer-name)))
+        (doc-view-doc->txt txt 'doc-view-open-text)))))
 
 ;;;;; Toggle between editing and viewing
 
@@ -1816,14 +1807,11 @@ doc-view-toggle-display
     (doc-view-fallback-mode)
     (doc-view-minor-mode 1))
    ((eq major-mode 'doc-view--text-view-mode)
-    (let ((buffer-undo-list t))
-      ;; We're currently viewing the document's text contents, so switch
-      ;; back to .
-      (setq buffer-read-only nil)
-      (insert-file-contents doc-view--buffer-file-name nil nil nil t)
-      (doc-view-fallback-mode)
-      (doc-view-minor-mode 1)
-      (set-buffer-modified-p nil)))
+    ;; We're currently viewing the document's text contents, switch to
+    ;; the buffer visiting the real document and kill myself.
+    (let ((dv-buffer (find-buffer-visiting doc-view--buffer-file-name)))
+      (kill-buffer)
+      (switch-to-buffer dv-buffer)))
    (t
     ;; Switch to doc-view-mode
     (when (and (buffer-modified-p)
-- 
2.45.2


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In GNU Emacs 31.0.50 (build 27, x86_64-unknown-openbsd7.5) of 2024-07-22
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-- 
Manuel Giraud

bug#72241: 31.0.50; [PATCH] Use a dedicated buffer for `doc-view-open-text'

[Tassilo Horn]

Manuel Giraud <manuel@ledu-giraud.fr> writes:

Hi Manuel,

> Here is a patch for DocView that makes it use a dedicated buffer for
> the text representation of a document.  This is what was suggested by
> Stefan M. in a comment (circa 2019).

I think that's a good idea in general and addresses a FIXME.

Since it doesn't fix a bug, I think it should only be applied to master.

Oh, and in the commit message there's an "an" where an "and" was meant.
And maybe a "text-contents buffer" is a slightly better term than "doc's
contents buffer".

I'm not sure if a NEWS entry is needed for that change.  It certainly
changes existing behavior but not in a way that usage patterns/muscle
memory would need to be adapted...

(info "(emacs) Document View") might need a small update for the
description where some requirement is not met (e.g., emacs in a TTY
frame) where it says that "the (document) buffer" is put in text mode
when one answers the query if the contents should be shown as plain text
with yes.

Bye,
  Tassilo

bug#72241: 31.0.50; [PATCH] Use a dedicated buffer for `doc-view-open-text'

[Eli Zaretskii]

> From: Tassilo Horn <tsdh@gnu.org>
> Date: Mon, 22 Jul 2024 20:11:34 +0200
> 
> I'm not sure if a NEWS entry is needed for that change.  It certainly
> changes existing behavior but not in a way that usage patterns/muscle
> memory would need to be adapted...

Can you tell in what way the behavior will change after this?  I'd
like to think whether a NEWS entry is necessary and what to day there.

Thanks.

bug#72241: 31.0.50; [PATCH] Use a dedicated buffer for `doc-view-open-text'

[Tassilo Horn]

Eli Zaretskii <eliz@gnu.org> writes:

>> From: Tassilo Horn <tsdh@gnu.org>
>> Date: Mon, 22 Jul 2024 20:11:34 +0200
>> 
>> I'm not sure if a NEWS entry is needed for that change.  It certainly
>> changes existing behavior but not in a way that usage patterns/muscle
>> memory would need to be adapted...
>
> Can you tell in what way the behavior will change after this?  I'd
> like to think whether a NEWS entry is necessary and what to day there.

Right now, when you open foo.pdf you see the images generated from the
PDF.  When you do C-c C-t, it'll replace the foo.pdf buffer contents
with the plain text contents of the PDF.  With another C-c C-c, the
contents are again replaced with the PDF and you see the images again.

With Manuel's patch, C-c C-t shows the plain text contents in a separate
buffer foo.pdf/text.  C-c C-c in there kills that separate buffer and
switches back to the original foo.pdf buffer.

So basically everything you have to do stays the same but there are now
two instead of just one buffer.  That has the advantage that you can
switch between them and removes the possibility that you accidentally
overwrite your PDF with the plain text contents (which in what Stefan's
FIXME was about).

Bye,
  Tassilo

bug#72241: 31.0.50; [PATCH] Use a dedicated buffer for `doc-view-open-text'

[Eli Zaretskii]

> From: Tassilo Horn <tsdh@gnu.org>
> Cc: 72241@debbugs.gnu.org,  manuel@ledu-giraud.fr
> Date: Mon, 22 Jul 2024 20:39:54 +0200
> 
> Eli Zaretskii <eliz@gnu.org> writes:
> 
> > Can you tell in what way the behavior will change after this?  I'd
> > like to think whether a NEWS entry is necessary and what to day there.
> 
> Right now, when you open foo.pdf you see the images generated from the
> PDF.  When you do C-c C-t, it'll replace the foo.pdf buffer contents
> with the plain text contents of the PDF.  With another C-c C-c, the
> contents are again replaced with the PDF and you see the images again.
> 
> With Manuel's patch, C-c C-t shows the plain text contents in a separate
> buffer foo.pdf/text.  C-c C-c in there kills that separate buffer and
> switches back to the original foo.pdf buffer.
> 
> So basically everything you have to do stays the same but there are now
> two instead of just one buffer.  That has the advantage that you can
> switch between them and removes the possibility that you accidentally
> overwrite your PDF with the plain text contents (which in what Stefan's
> FIXME was about).

Thanks, I think this is enough in users' faces to warrant a NEWS
entry.

bug#72241: 31.0.50; [PATCH] Use a dedicated buffer for `doc-view-open-text'

[Manuel Giraud via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Tassilo Horn <tsdh@gnu.org> writes:

> Eli Zaretskii <eliz@gnu.org> writes:
>
>>> From: Tassilo Horn <tsdh@gnu.org>
>>> Date: Mon, 22 Jul 2024 20:11:34 +0200
>>> 
>>> I'm not sure if a NEWS entry is needed for that change.  It certainly
>>> changes existing behavior but not in a way that usage patterns/muscle
>>> memory would need to be adapted...
>>
>> Can you tell in what way the behavior will change after this?  I'd
>> like to think whether a NEWS entry is necessary and what to day there.
>
> Right now, when you open foo.pdf you see the images generated from the
> PDF.  When you do C-c C-t, it'll replace the foo.pdf buffer contents
> with the plain text contents of the PDF.  With another C-c C-c, the
> contents are again replaced with the PDF and you see the images again.

FWIW, this is not the current behaviour that I see:

      - C-c C-t replace the buffer contents with the text version
      
      - C-c C-c, DocView switches back to the "edit" view: the raw
        content of a PDF for instance is displayed into the buffer.

      - another C-c C-c, DocView switches to the "display" view where
        you see the images again

Maybe while here, we should clarify how DocView cycles through those 3
view: display, edit and text.  Or maybe, there is no 3-states cycling
and the "text contents" view is just considered a "side" view.  WDYT?
-- 
Manuel Giraud

bug#72241: 31.0.50; [PATCH] Use a dedicated buffer for `doc-view-open-text'

[Tassilo Horn]

Manuel Giraud <manuel@ledu-giraud.fr> writes:

Hi,

>>> Can you tell in what way the behavior will change after this?  I'd
>>> like to think whether a NEWS entry is necessary and what to day there.
>>
>> Right now, when you open foo.pdf you see the images generated from
>> the PDF.  When you do C-c C-t, it'll replace the foo.pdf buffer
>> contents with the plain text contents of the PDF.  With another C-c
>> C-c, the contents are again replaced with the PDF and you see the
>> images again.
>
> FWIW, this is not the current behaviour that I see:
>
>       - C-c C-t replace the buffer contents with the text version
>       
>       - C-c C-c, DocView switches back to the "edit" view: the raw
>         content of a PDF for instance is displayed into the buffer.
>
>       - another C-c C-c, DocView switches to the "display" view where
>         you see the images again

That's right and my answer was aproximately correct.  The beef is that
for the "text version", you get a separate buffer with your patch.
"edit" and "display" are in the same buffer because the contents (raw
PDF, DVI, PostScript,...) are the same, just how they are presented to
the user differs.

> Maybe while here, we should clarify how DocView cycles through those 3
> view: display, edit and text.  Or maybe, there is no 3-states cycling
> and the "text contents" view is just considered a "side" view.  WDYT?

Here's a state machine describing the current behavior.

    display <-- C-c C-c --> edit
    \     ^
     \     \    
 C-c C-t  C-c C-c
       \     \
        `> text

So with C-c C-c you can toggle between "display" and "edit" which just
changes how the buffer contents are presented to the user (images or raw
text).

In the "display" state C-c C-t one gets a plain text version of the
contents, and that's in a separate foo.pdf/text buffer with Manuel's
patch.  In there, C-c C-c kills the foo.pdf/text buffer and returns to
the original foo.pdf buffer.

However, that now one can switch between foo.pdf and foo.pdf/text
independently, there is no guarantee that C-c C-c in the foo.pdf/text
buffer will return to foo.pdf in "display" state.  One could have
toggled to edit state there or even killed the foo.pdf buffer, so
there's nothing to return to.

So I'd say: right now it is a state machine with 3 states but with
Manuel's patch the current "text" state becomes an auxiliary view.

Bye,
  Tassilo

bug#72241: 31.0.50; [PATCH] Use a dedicated buffer for `doc-view-open-text'

[Manuel Giraud via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Tassilo Horn <tsdh@gnu.org> writes:

[...]

>> Maybe while here, we should clarify how DocView cycles through those 3
>> view: display, edit and text.  Or maybe, there is no 3-states cycling
>> and the "text contents" view is just considered a "side" view.  WDYT?
>
> Here's a state machine describing the current behavior.
>
>     display <-- C-c C-c --> edit
>     \     ^
>      \     \
>  C-c C-t  C-c C-c
>        \     \
>         `> text

I think the current behavior is more like this (I suck at ASCII art):

    display <-- C-c C-c --> edit
    \                      ^
     \                  /--
 C-c C-t            C-c C-c
       \        /--
        `> text

Your state machine is what my patch gives you.

[...]

> However, that now one can switch between foo.pdf and foo.pdf/text
> independently, there is no guarantee that C-c C-c in the foo.pdf/text
> buffer will return to foo.pdf in "display" state.  One could have
> toggled to edit state there or even killed the foo.pdf buffer, so
> there's nothing to return to.

Yes, you're right.  In the latter case (the foo.pdf buffer was killed
otherwise), a C-c C-c in the foo.pdf/text buffer just kill it, go to
another buffer and the document is not open anywhere in any form.  Maybe
it is a not so bad behavior.

> So I'd say: right now it is a state machine with 3 states but with
> Manuel's patch the current "text" state becomes an auxiliary view.

Yes.  So I'm going to try to fix my patch with your remarks (maybe fix
the info also) and come up with a NEWS entry.  Thanks.
-- 
Manuel Giraud

bug#72241: 31.0.50; [PATCH] Use a dedicated buffer for `doc-view-open-text'

[Tassilo Horn]

Manuel Giraud <manuel@ledu-giraud.fr> writes:

>> Here's a state machine describing the current behavior.
>>
>>     display <-- C-c C-c --> edit
>>     \     ^
>>      \     \
>>  C-c C-t  C-c C-c
>>        \     \
>>         `> text
>
> I think the current behavior is more like this (I suck at ASCII art):
>
>     display <-- C-c C-c --> edit
>     \                      ^
>      \                  /--
>  C-c C-t            C-c C-c
>        \        /--
>         `> text

You are right.

>> However, that now one can switch between foo.pdf and foo.pdf/text
>> independently, there is no guarantee that C-c C-c in the foo.pdf/text
>> buffer will return to foo.pdf in "display" state.  One could have
>> toggled to edit state there or even killed the foo.pdf buffer, so
>> there's nothing to return to.
>
> Yes, you're right.  In the latter case (the foo.pdf buffer was killed
> otherwise), a C-c C-c in the foo.pdf/text buffer just kill it, go to
> another buffer and the document is not open anywhere in any form.
> Maybe it is a not so bad behavior.

No, I think that's ok.

>> So I'd say: right now it is a state machine with 3 states but with
>> Manuel's patch the current "text" state becomes an auxiliary view.
>
> Yes.  So I'm going to try to fix my patch with your remarks (maybe fix
> the info also) and come up with a NEWS entry.  Thanks.

Great, thanks!

Bye,
  Tassilo

bug#72241: 31.0.50; [PATCH] Use a dedicated buffer for `doc-view-open-text'

[Manuel Giraud via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Tassilo Horn <tsdh@gnu.org> writes:

[...]

>> Yes.  So I'm going to try to fix my patch with your remarks (maybe fix
>> the info also) and come up with a NEWS entry.  Thanks.
>
> Great, thanks!

Hi again,

I don't think I'm going to modify the info page with this patch.  I've
just tested on TTY emacs to open a PDF and both without and with my
patch DocView does not load and the buffer stays in fundamental-mode.
So I guess, we need more work in this area.
-- 
Manuel Giraud

bug#72241: 31.0.50; [PATCH] Use a dedicated buffer for `doc-view-open-text'

[Manuel Giraud via Bug reports for GNU Emacs, the Swiss army knife of text editors]

[-- Attachment #1: Type: text/plain, Size: 49 bytes --]

Here is an updated version of this patch.  WDYT?

[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: 0001-Use-a-dedicated-buffer-for-doc-view-open-text.patch --]
[-- Type: text/x-patch, Size: 4704 bytes --]

From 6e32534012cafeda1d7e67aab23a8206bc887c9f Mon Sep 17 00:00:00 2001
From: Manuel Giraud <manuel@ledu-giraud.fr>
Date: Sun, 21 Jul 2024 18:52:52 +0200
Subject: [PATCH] Use a dedicated buffer for `doc-view-open-text'

* lisp/doc-view.el (doc-view-open-text): Create a new "text
contents" buffer and switch to it.
(doc-view-toggle-display): Switch back to the document buffer
and kill the "text contents" one.
* etc/NEWS: Mention the change.
---
 etc/NEWS         |  7 ++++++
 lisp/doc-view.el | 60 +++++++++++++++++++-----------------------------
 2 files changed, 31 insertions(+), 36 deletions(-)

diff --git a/etc/NEWS b/etc/NEWS
index d683db606ec..81382200eef 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -149,6 +149,13 @@ This affects calls to 'warn', 'lwarn', 'display-warning', and
 In most cases, having it enabled leads to a large amount of false
 positives.
 
+** DocView
+
+---
+*** Dedicated buffer for plain text contents.
+When switching to the plain text contents with 'doc-view-open-text',
+DocView now creates a dedicated buffer to display it. 'C-c C-c' gets you
+back to real DocView buffer if it still exists.
 \f
 * New Modes and Packages in Emacs 31.1
 
diff --git a/lisp/doc-view.el b/lisp/doc-view.el
index 801783bd766..6313ee83857 100644
--- a/lisp/doc-view.el
+++ b/lisp/doc-view.el
@@ -1768,34 +1768,25 @@ doc-view-open-text
     (let ((txt (expand-file-name "doc.txt" (doc-view--current-cache-dir)))
           (page (doc-view-current-page)))
       (if (file-readable-p txt)
-	  (let ((inhibit-read-only t)
-		(buffer-undo-list t)
-		(dv-bfn doc-view--buffer-file-name))
-	    (erase-buffer)
-            ;; FIXME: Replacing the buffer's PDF content with its txt rendering
-            ;; is pretty risky.  We should probably use *another*
-            ;; buffer instead, so there's much less risk of
-            ;; overwriting the PDF file with some text rendering.
-	    (set-buffer-multibyte t)
-	    (insert-file-contents txt)
-	    (doc-view--text-view-mode)
-	    (setq-local doc-view--buffer-file-name dv-bfn)
-	    (set-buffer-modified-p nil)
-	    (doc-view-minor-mode)
-            (goto-char (point-min))
-            ;; Put point at the start of the page the user was
-            ;; reading.  Pages are separated by Control-L characters.
-            (re-search-forward page-delimiter nil t (1- page))
-	    (add-hook 'write-file-functions
-		      (lambda ()
-                        ;; FIXME: If the user changes major mode and then
-                        ;; saves the buffer, the PDF file will be clobbered
-                        ;; with its txt rendering!
-			(when (eq major-mode 'doc-view--text-view-mode)
-			  (error "Cannot save text contents of document %s"
-				 buffer-file-name)))
-		      nil t))
-	(doc-view-doc->txt txt 'doc-view-open-text)))))
+          (let ((dv-bfn doc-view--buffer-file-name)
+                (dv-text-buffer-name (format "%s/text" (buffer-name))))
+            ;; Prepare the text buffer
+            (with-current-buffer (get-buffer-create dv-text-buffer-name)
+              (let ((inhibit-read-only t)
+                    (buffer-undo-list t))
+                (erase-buffer)
+                (set-buffer-multibyte t)
+                (insert-file-contents txt)
+                (doc-view--text-view-mode)
+                (setq-local doc-view--buffer-file-name dv-bfn)
+                (set-buffer-modified-p nil)
+                (doc-view-minor-mode)
+                (goto-char (point-min))
+                ;; Put point at the start of the page the user was
+                ;; reading.  Pages are separated by Control-L characters.
+                (re-search-forward page-delimiter nil t (1- page))))
+            (switch-to-buffer (get-buffer dv-text-buffer-name)))
+        (doc-view-doc->txt txt 'doc-view-open-text)))))
 
 ;;;;; Toggle between editing and viewing
 
@@ -1816,14 +1807,11 @@ doc-view-toggle-display
     (doc-view-fallback-mode)
     (doc-view-minor-mode 1))
    ((eq major-mode 'doc-view--text-view-mode)
-    (let ((buffer-undo-list t))
-      ;; We're currently viewing the document's text contents, so switch
-      ;; back to .
-      (setq buffer-read-only nil)
-      (insert-file-contents doc-view--buffer-file-name nil nil nil t)
-      (doc-view-fallback-mode)
-      (doc-view-minor-mode 1)
-      (set-buffer-modified-p nil)))
+    ;; We're currently viewing the document's text contents, switch to
+    ;; the buffer visiting the real document and kill myself.
+    (let ((dv-buffer (find-buffer-visiting doc-view--buffer-file-name)))
+      (kill-buffer)
+      (switch-to-buffer dv-buffer)))
    (t
     ;; Switch to doc-view-mode
     (when (and (buffer-modified-p)
-- 
2.45.2


[-- Attachment #3: Type: text/plain, Size: 18 bytes --]

-- 
Manuel Giraud

bug#72241: 31.0.50; [PATCH] Use a dedicated buffer for `doc-view-open-text'

[Tassilo Horn]

Manuel Giraud <manuel@ledu-giraud.fr> writes:

Hi Manuel,

> Here is an updated version of this patch.  WDYT?

Looks and works good.  Applied and pushed to master.  I have also
adjusted the info docs slightly so that it says that the text contents
are displayed in a separate buffed with /text suffix.

Thanks again!
  Tassilo

bug#72241: 31.0.50; [PATCH] Use a dedicated buffer for `doc-view-open-text'

[Manuel Giraud via Bug reports for GNU Emacs, the Swiss army knife of text editors]

Tassilo Horn <tsdh@gnu.org> writes:

> Manuel Giraud <manuel@ledu-giraud.fr> writes:
>
> Hi Manuel,
>
>> Here is a patch for DocView that makes it use a dedicated buffer for
>> the text representation of a document.  This is what was suggested by
>> Stefan M. in a comment (circa 2019).
>
> I think that's a good idea in general and addresses a FIXME.
>
> Since it doesn't fix a bug, I think it should only be applied to
> master.

Yes, I also do think so.

> Oh, and in the commit message there's an "an" where an "and" was meant.
> And maybe a "text-contents buffer" is a slightly better term than "doc's
> contents buffer".

Ok.  I'll fix that.

[...]

> (info "(emacs) Document View") might need a small update for the
> description where some requirement is not met (e.g., emacs in a TTY
> frame) where it says that "the (document) buffer" is put in text mode
> when one answers the query if the contents should be shown as plain text
> with yes.

I have not tested in a TTY… maybe I should 😅
-- 
Manuel Giraud