bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

[Visuwesh]

Pretty much the subject.

1. emacs -Q.
2. Open a pdf file.
3. Clone the tab using C-x t n.
4. Move to the next page (n).
5. Switch back to the original tab C-x t o.
6. The page is changed here too.

Expected: The original and the cloned tabs should show different pages,
just like how you can show different pages in different windows/frames.

[ FWIW, the same problem also exists with pdf-tools.  ]

In GNU Emacs 29.0.50 (build 1, x86_64-pc-linux-gnu, X toolkit, cairo version 1.16.0, Xaw scroll bars)
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bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

[Juri Linkov]

> Pretty much the subject.
>
> 1. emacs -Q.
> 2. Open a pdf file.
> 3. Clone the tab using C-x t n.
> 4. Move to the next page (n).
> 5. Switch back to the original tab C-x t o.
> 6. The page is changed here too.
>
> Expected: The original and the cloned tabs should show different pages,
> just like how you can show different pages in different windows/frames.
>
> [ FWIW, the same problem also exists with pdf-tools.  ]

This is expected behavior when you use 'C-x t n' that clones
the current tab.  A new clone has exactly the same window.
You can confirm this by evaluating in each tab: 'M-: (selected-window)'.
It will show the same window number.  But doc-view can show different pages
only in different windows.

bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

[Visuwesh]

[வியாழன், பிப்ரவரி 17 2022] Juri Linkov wrote:

>> Pretty much the subject.
>>
>> 1. emacs -Q.
>> 2. Open a pdf file.
>> 3. Clone the tab using C-x t n.
>> 4. Move to the next page (n).
>> 5. Switch back to the original tab C-x t o.
>> 6. The page is changed here too.
>>
>> Expected: The original and the cloned tabs should show different pages,
>> just like how you can show different pages in different windows/frames.
>>
>> [ FWIW, the same problem also exists with pdf-tools.  ]
>
> This is expected behavior when you use 'C-x t n' that clones
> the current tab.  A new clone has exactly the same window.
> You can confirm this by evaluating in each tab: 'M-:
> (selected-window)'.
> It will show the same window number.  But doc-view can show different pages
> only in different windows.

I see, thanks.  I didn't know that.  If that is the case, the current
behaviour makes sense.  I was confused primarily because tabs created
this showing regular buffers were allowed to have different points.

But, how can I get my desired behaviour tho?  If I create a new tab
using C-x t 2, it breaks doc-view in a different way.  I am finding it
hard to describe it in text, so I would appreciate it if you can try it
out for yourself: essentially, C-x t 2, and then try changing pages.
Doc-view doesn't show the correct image but the page number in the
modeline changes.

bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

[Juri Linkov]

>>> 2. Open a pdf file.
>>> 3. Clone the tab using C-x t n.
>>> 4. Move to the next page (n).
>>> 5. Switch back to the original tab C-x t o.
>>> 6. The page is changed here too.
>>>
>>> Expected: The original and the cloned tabs should show different pages,
>>> just like how you can show different pages in different windows/frames.
>>
>> This is expected behavior when you use 'C-x t n' that clones
>> the current tab.  A new clone has exactly the same window.
>> You can confirm this by evaluating in each tab: 'M-:
>> (selected-window)'.
>> It will show the same window number.  But doc-view can show different pages
>> only in different windows.
>
> I see, thanks.  I didn't know that.  If that is the case, the current
> behaviour makes sense.  I was confused primarily because tabs created
> this showing regular buffers were allowed to have different points.

Hmm, maybe 'C-x t n' should not reuse the same window,
but should create a new window with exactly the same state.
This will avoid such problems.  Ok, I'll try to use
window-state-put/get while cloning tabs.

> But, how can I get my desired behaviour tho?  If I create a new tab
> using C-x t 2, it breaks doc-view in a different way.  I am finding it
> hard to describe it in text, so I would appreciate it if you can try it
> out for yourself: essentially, C-x t 2, and then try changing pages.
> Doc-view doesn't show the correct image but the page number in the
> modeline changes.

You are right, it fails with 'C-x t 2' too, so there is a problem
in interaction between doc-view and tab switching.  The current
handling of different windows in doc-view is quite hackish,
so it should be rewritten.  This comment in doc-view.el
proposes a good idea how this should be properly implemented:

      ;; FIXME: This should be done for all windows restored that show
      ;; this buffer.  Basically, the page/slice should be saved as
      ;; window-parameters in the window-state(s) and then restoring this
      ;; window-state should call us back (to interpret/use those parameters).

bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

[Juri Linkov]

[-- Attachment #1: Type: text/plain, Size: 674 bytes --]

> Hmm, maybe 'C-x t n' should not reuse the same window,
> but should create a new window with exactly the same state.
> This will avoid such problems.  Ok, I'll try to use
> window-state-put/get while cloning tabs.

Here is attempt to create new windows with 'C-x t n'.
It works fine with (window-state-put (window-state-get))
to clone all windows in the tab (from the frame window).

But 'tab-bar-move-window-to-tab' still doesn't work
when it binds 'tab-bar-new-tab-choice' to 'window'.

The problem is that this doesn't create a new window
from the selected window:

  (window-state-put (window-state-get (selected-window)) (selected-window))

Maybe Martin could help.


[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #2: tab-bar-new-tab-choice-clone.patch --]
[-- Type: text/x-diff, Size: 2721 bytes --]

diff --git a/lisp/tab-bar.el b/lisp/tab-bar.el
index e88bcac0da..7185cd52e8 100644
--- a/lisp/tab-bar.el
+++ b/lisp/tab-bar.el
@@ -481,7 +481,7 @@ tab-bar-new-tab-choice
 if such buffer exists, or switch to a buffer visiting the file or
 directory that the string specifies.  If the value is a function,
 call it with no arguments and switch to the buffer that it returns.
-If nil, duplicate the contents of the tab that was active
+If `clone', duplicate the contents of the tab that was active
 before calling the command that adds a new tab."
   :type '(choice (const     :tag "Current buffer" t)
                  (const     :tag "Current window" window)
@@ -489,7 +489,7 @@ tab-bar-new-tab-choice
                  (directory :tag "Directory" :value "~/")
                  (file      :tag "File" :value "~/.emacs")
                  (function  :tag "Function")
-                 (const     :tag "Duplicate tab" nil))
+                 (const     :tag "Duplicate tab" clone))
   :group 'tab-bar
   :version "27.1")
 
@@ -1367,14 +1367,19 @@ tab-bar-new-tab-to
         (select-window (minibuffer-selected-window)))
       ;; Remove window parameters that can cause problems
       ;; with `delete-other-windows' and `split-window'.
-      (set-window-parameter nil 'window-atom nil)
-      (set-window-parameter nil 'window-side nil)
+      (unless (eq tab-bar-new-tab-choice 'clone)
+        (set-window-parameter nil 'window-atom nil)
+        (set-window-parameter nil 'window-side nil))
       (let ((ignore-window-parameters t))
-        (delete-other-windows)
-        (unless (eq tab-bar-new-tab-choice 'window)
-          ;; Create a new window to get rid of old window parameters
-          ;; (e.g. prev/next buffers) of old window.
-          (split-window) (delete-window)))
+        (if (eq tab-bar-new-tab-choice 'clone)
+            (window-state-put (window-state-get))
+          (delete-other-windows)
+          (if (eq tab-bar-new-tab-choice 'window)
+              ;; TODO: this doesn't create a new window
+              (window-state-put (window-state-get (selected-window)) (selected-window))
+            ;; Create a new window to get rid of old window parameters
+            ;; (e.g. prev/next buffers) of old window.
+            (split-window) (delete-window))))
 
       (let ((buffer
              (if (functionp tab-bar-new-tab-choice)
@@ -1453,7 +1458,7 @@ tab-bar-duplicate-tab
   "Clone the current tab to ARG positions to the right.
 ARG and FROM-NUMBER have the same meaning as in `tab-bar-new-tab'."
   (interactive "P")
-  (let ((tab-bar-new-tab-choice nil)
+  (let ((tab-bar-new-tab-choice 'clone)
         (tab-bar-new-tab-group t))
     (tab-bar-new-tab arg from-number)))
 

bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

[martin rudalics]

 > The problem is that this doesn't create a new window
 > from the selected window:
 >
 >    (window-state-put (window-state-get (selected-window)) (selected-window))

This should put the contents of the selected window into itself - a NOOP
WOW.  What else did you expect?

martin

bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

[Juri Linkov]

>> The problem is that this doesn't create a new window
>> from the selected window:
>>
>>    (window-state-put (window-state-get (selected-window)) (selected-window))
>
> This should put the contents of the selected window into itself - a NOOP
> WOW.  What else did you expect?

Thanks, now this is simplified in master.

bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

[Juri Linkov]

> But, how can I get my desired behaviour tho?  If I create a new tab
> using C-x t 2, it breaks doc-view in a different way.  I am finding it
> hard to describe it in text, so I would appreciate it if you can try it
> out for yourself: essentially, C-x t 2, and then try changing pages.
> Doc-view doesn't show the correct image but the page number in the
> modeline changes.

Please try this patch with 'C-x t 2' (whereas 'C-x t n' will be fixed later).
The problem is that when 'image-mode-winprops' does window cleanup,
it doesn't take into account windows saved in tabs.

diff --git a/lisp/image-mode.el b/lisp/image-mode.el
index 5bee155460..c127df12ae 100644
--- a/lisp/image-mode.el
+++ b/lisp/image-mode.el
@@ -179,7 +179,7 @@ image-mode-reapply-winprops
     ;; Beware: this call to image-mode-winprops can't be optimized away,
     ;; because it not only gets the winprops data but sets it up if needed
     ;; (e.g. it's used by doc-view to display the image in a new window).
-    (let* ((winprops (image-mode-winprops nil t))
+    (let* ((winprops (image-mode-winprops nil nil))
            (hscroll (image-mode-window-get 'hscroll winprops))
            (vscroll (image-mode-window-get 'vscroll winprops)))
       (when (image-get-display-property) ;Only do it if we display an image!

bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

[Visuwesh]

[வெள்ளி, பிப்ரவரி 18 2022] Juri Linkov wrote:

>> But, how can I get my desired behaviour tho?  If I create a new tab
>> using C-x t 2, it breaks doc-view in a different way.  I am finding it
>> hard to describe it in text, so I would appreciate it if you can try it
>> out for yourself: essentially, C-x t 2, and then try changing pages.
>> Doc-view doesn't show the correct image but the page number in the
>> modeline changes.
>
> Please try this patch with 'C-x t 2' (whereas 'C-x t n' will be fixed later).
> The problem is that when 'image-mode-winprops' does window cleanup,
> it doesn't take into account windows saved in tabs.
>

Doc-view is still broken here.  But now the tabs at least show different
pages but they break in a similar way as before.

Also, unfortunately, this completely breaks pdf-tools (one tab shows the
image, the other shows the raw PDF file).  Considering that it is in
NonGNU ELPA, it would be nice to ensure that it isn't broken.

bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

[Juri Linkov]

> The problem is that when 'image-mode-winprops' does window cleanup,
> it doesn't take into account windows saved in tabs.

The current implementation:

  (when cleanup
    (setq image-mode-winprops-alist
  	  (delq nil (mapcar (lambda (winprop)
			      (let ((w (car-safe winprop)))
				(if (or (not (windowp w)) (window-live-p w))
				    winprop)))
  			    image-mode-winprops-alist))))


'window-live-p' doesn't check windows saved in window-configurations in tabs.

Maybe it should check tab window-configurations on all frames
by a new function 'window-configuration-windows'
(something like used in 'tab-bar-get-buffer-tab').

But then what about windows saved by 'window-configuration-to-register'?
Should they be checked by 'window-live-p' too?

Or maybe better to change 'image-mode-winprops-alist' to the hash
'image-mode-winprops-hash' where window keys are garbage-collected?
So when a window is deleted from all window-configurations,
it will be garbage-collected?

bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

[martin rudalics]

 > 'window-live-p' doesn't check windows saved in window-configurations in tabs.
 >
 > Maybe it should check tab window-configurations on all frames
 > by a new function 'window-configuration-windows'
 > (something like used in 'tab-bar-get-buffer-tab').
 >
 > But then what about windows saved by 'window-configuration-to-register'?
 > Should they be checked by 'window-live-p' too?
 >
 > Or maybe better to change 'image-mode-winprops-alist' to the hash
 > 'image-mode-winprops-hash' where window keys are garbage-collected?
 > So when a window is deleted from all window-configurations,
 > it will be garbage-collected?

GC tries to remove dead buffers window configurations stored in their
list of previous or next buffers.  But checking for whether a dead
window has disappeared from all stored configurations is more demanding
- maybe we could reserve a bit in each window the collector resets for
all dead windows at the beginning of each cycle and at the end reclaim
the space of all windows that did not have that bit set when the window
was found in a stored window configuration.

martin

bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

[Juri Linkov]

>> 'window-live-p' doesn't check windows saved in window-configurations in tabs.
>>
>> Maybe it should check tab window-configurations on all frames
>> by a new function 'window-configuration-windows'
>> (something like used in 'tab-bar-get-buffer-tab').
>>
>> But then what about windows saved by 'window-configuration-to-register'?
>> Should they be checked by 'window-live-p' too?
>>
>> Or maybe better to change 'image-mode-winprops-alist' to the hash
>> 'image-mode-winprops-hash' where window keys are garbage-collected?
>> So when a window is deleted from all window-configurations,
>> it will be garbage-collected?
>
> GC tries to remove dead buffers window configurations stored in their
> list of previous or next buffers.  But checking for whether a dead
> window has disappeared from all stored configurations is more demanding
> - maybe we could reserve a bit in each window the collector resets for
> all dead windows at the beginning of each cycle and at the end reclaim
> the space of all windows that did not have that bit set when the window
> was found in a stored window configuration.

Maybe a more immediate solution would be simply to iterate all tabs
on all frames, and to check whether they contain a window.  But still
I can't find a function to check whether a window is in a window configuration.
Does such a function exist?

bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

[martin rudalics]

 > Maybe a more immediate solution would be simply to iterate all tabs
 > on all frames, and to check whether they contain a window.  But still
 > I can't find a function to check whether a window is in a window configuration.
 > Does such a function exist?

No.  The only agent that has access to all window configurations is the
garbage collector.  Do you want to collect garbage each time you want to
know whether a window is part of a window configuration?

martin

bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

[Juri Linkov]

>> Maybe a more immediate solution would be simply to iterate all tabs
>> on all frames, and to check whether they contain a window.  But still
>> I can't find a function to check whether a window is in a window configuration.
>> Does such a function exist?
>
> No.  The only agent that has access to all window configurations is the
> garbage collector.  Do you want to collect garbage each time you want to
> know whether a window is part of a window configuration?
>
>> Like in bug#54038 (about having access to windows in window configurations),
>> the problem is that there is no way to update and even peek inside
>> a window configuration.  In bug#54038 the cleanup function can't tell
>> if a window is still live in a window configuration.
>
> We might be able to provide such a function but can you tell me why you
> would need it and how you would use it?

It could be used in 'image-mode-winprops':

  (when cleanup
    (setq image-mode-winprops-alist
  	  (delq nil (mapcar (lambda (winprop)
			      (let ((w (car-safe winprop)))
				(if (or (not (windowp w))
                                        (window-live-p w)
           new function =>              (window-live-in-all-window-configurations w))
				    winprop)))
  			    image-mode-winprops-alist))))

bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

[martin rudalics]

 >> We might be able to provide such a function but can you tell me why you
 >> would need it and how you would use it?
 >
 > It could be used in 'image-mode-winprops':
 >
 >    (when cleanup
 >      (setq image-mode-winprops-alist
 >    	  (delq nil (mapcar (lambda (winprop)
 > 			      (let ((w (car-safe winprop)))
 > 				(if (or (not (windowp w))
 >                                          (window-live-p w)
 >             new function =>              (window-live-in-all-window-configurations w))
 > 				    winprop)))
 >    			    image-mode-winprops-alist))))

I can't tell from here what 'window-live-in-all-window-configurations'
is supposed to return.  Its name appears misleading - do we care if 'w'
is live in a configuration of another frame but w's?  So please tell me
the doc-string of ‘window-live-in-all-window-configurations’ first.

And please always keep in mind: The only agent that has access to _all_
window configurations is the garbage collector.  If we wanted to change
that, we'd have to make window configurations explicitly deletable like
buffers or windows with functions like 'make-window-configuration',
'delete-window-configuration' and 'window-configurations-list'.  While
this might not pose great problems for read_minibuf, it certainly will
for configurations in plain Lisp code which all of a sudden would become
noncollectable after the last reference to them has gone ...

martin

bug#54038: 29.0.50; doc-view cannot show different pages in different tabs

[Juri Linkov]

> The problem is that when 'image-mode-winprops' does window cleanup,
> it doesn't take into account windows saved in tabs.
>
> diff --git a/lisp/image-mode.el b/lisp/image-mode.el
> index 5bee155460..c127df12ae 100644
> --- a/lisp/image-mode.el
> +++ b/lisp/image-mode.el
> @@ -179,7 +179,7 @@ image-mode-reapply-winprops
>      ;; Beware: this call to image-mode-winprops can't be optimized away,
>      ;; because it not only gets the winprops data but sets it up if needed
>      ;; (e.g. it's used by doc-view to display the image in a new window).
> -    (let* ((winprops (image-mode-winprops nil t))
> +    (let* ((winprops (image-mode-winprops nil nil))
>             (hscroll (image-mode-window-get 'hscroll winprops))
>             (vscroll (image-mode-window-get 'vscroll winprops)))
>        (when (image-get-display-property) ;Only do it if we display an image!

I see that Po Lu corrected display of Doc View documents after tab switching
in the commit a475360af98.  I tried the original report, but it still doesn't
work without the patch above.