bug#54450: 29.0.50; redisplay--pre-redisplay-functions issue

bug#54450: 29.0.50; redisplay--pre-redisplay-functions issue

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

Hi:

As discussed in emacs develop, it seems like the display engine is not
fully running redisplay--pre-redisplay-functions when moving point in
not active windows.

To reproduce:

emacs -Q
(setq highlight-nonselected-windows t)

C-x 2
C-x o
C-x C-f /tmp/test
(insert some text)
C-a C-SPC C-f C-f C-f
C-x o 

[at this point we should see a region highlighted over the 3 first
letters of the inserted text in the other winfow buffer (test)]

then eval this several times:

(with-selected-window (get-buffer-window "test" 0)
    (right-char))

This will move the point in the test window, but the region won't be
updated.




In GNU Emacs 29.0.50 (build 129, x86_64-pc-linux-gnu, GTK+ Version 3.24.33, cairo version 1.17.4)
 of 2022-03-18 built on Ergus
Repository revision: 04350dc2f56b405bc9d1c7046ad5523b3ff23591
Repository branch: feature/completions-customs
System Description: Arch Linux

Configured using:
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Load-path shadows:
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bug#54450: 29.0.50; redisplay--pre-redisplay-functions issue

[Eli Zaretskii]

> Date: Fri, 18 Mar 2022 16:38:45 +0100
> From:  Ergus via "Bug reports for GNU Emacs,
>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
> 
> emacs -Q
> (setq highlight-nonselected-windows t)
> 
> C-x 2
> C-x o
> C-x C-f /tmp/test
> (insert some text)
> C-a C-SPC C-f C-f C-f
> C-x o 
> 
> [at this point we should see a region highlighted over the 3 first
> letters of the inserted text in the other winfow buffer (test)]
> 
> then eval this several times:
> 
> (with-selected-window (get-buffer-window "test" 0)
>     (right-char))
> 
> This will move the point in the test window, but the region won't be
> updated.

Thanks.  Does the patch below solve the problem?

diff --git a/src/intervals.c b/src/intervals.c
index 687b237..cbcc100 100644
--- a/src/intervals.c
+++ b/src/intervals.c
@@ -44,6 +44,7 @@
 #include "lisp.h"
 #include "intervals.h"
 #include "buffer.h"
+#include "window.h"
 #include "puresize.h"
 #include "keymap.h"
 
@@ -1885,6 +1886,11 @@ set_point_both (ptrdiff_t charpos, ptrdiff_t bytepos)
       return;
     }
 
+  if (highlight_nonselected_windows
+      && !NILP (Vtransient_mark_mode)
+      && !NILP (BVAR (current_buffer, mark_active)))
+    bset_redisplay (current_buffer);
+
   /* Set TO to the interval containing the char after CHARPOS,
      and TOPREV to the interval containing the char before CHARPOS.
      Either one may be null.  They may be equal.  */

bug#54450: 29.0.50; redisplay--pre-redisplay-functions issue

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

On Fri, Mar 18, 2022 at 07:01:06PM +0200, Eli Zaretskii wrote:
>> Date: Fri, 18 Mar 2022 16:38:45 +0100
>> From:  Ergus via "Bug reports for GNU Emacs,
>>  the Swiss army knife of text editors" <bug-gnu-emacs@gnu.org>
>>
>> emacs -Q
>> (setq highlight-nonselected-windows t)
>>
>> C-x 2
>> C-x o
>> C-x C-f /tmp/test
>> (insert some text)
>> C-a C-SPC C-f C-f C-f
>> C-x o
>>
>> [at this point we should see a region highlighted over the 3 first
>> letters of the inserted text in the other winfow buffer (test)]
>>
>> then eval this several times:
>>
>> (with-selected-window (get-buffer-window "test" 0)
>>     (right-char))
>>
>> This will move the point in the test window, but the region won't be
>> updated.
>
>Thanks.  Does the patch below solve the problem?
>
>diff --git a/src/intervals.c b/src/intervals.c
>index 687b237..cbcc100 100644
>--- a/src/intervals.c
>+++ b/src/intervals.c
>@@ -44,6 +44,7 @@
> #include "lisp.h"
> #include "intervals.h"
> #include "buffer.h"
>+#include "window.h"
> #include "puresize.h"
> #include "keymap.h"
>
>@@ -1885,6 +1886,11 @@ set_point_both (ptrdiff_t charpos, ptrdiff_t bytepos)
>       return;
>     }
>
>+  if (highlight_nonselected_windows
>+      && !NILP (Vtransient_mark_mode)
>+      && !NILP (BVAR (current_buffer, mark_active)))
>+    bset_redisplay (current_buffer);
>+
>   /* Set TO to the interval containing the char after CHARPOS,
>      and TOPREV to the interval containing the char before CHARPOS.
>      Either one may be null.  They may be equal.  */

Hi Eli:

Yes, this could solve the issue for the region, but not in general for
redisplay--update-cursor-face-highlight which was the initial problem
with Juri's code. Same for any other function that goes into the
pre-redisplay-functions hook.

The region example reported in this issue was only the simplest way I
found to give you a simple reproducible snippet, but the issue is a bit
more general.

With the cursor-face we may have a similar issue cause such hook works
in the same way, so this condition will need to be extended and extended
and extended on every case for every function in
pre-redisplay-functions hook.

else

For Juri's code maybe there is a way that he can explicitly do
bset_redisplay at the end of the with-selected-window?

Does it makes sense?

Best,
Ergus

bug#54450: 29.0.50; redisplay--pre-redisplay-functions issue

[Eli Zaretskii]

> Date: Fri, 18 Mar 2022 18:42:52 +0100
> From: Ergus <spacibba@aol.com>
> Cc: 54450@debbugs.gnu.org
> 
> >+  if (highlight_nonselected_windows
> >+      && !NILP (Vtransient_mark_mode)
> >+      && !NILP (BVAR (current_buffer, mark_active)))
> >+    bset_redisplay (current_buffer);
> >+
> >   /* Set TO to the interval containing the char after CHARPOS,
> >      and TOPREV to the interval containing the char before CHARPOS.
> >      Either one may be null.  They may be equal.  */
> 
> Hi Eli:
> 
> Yes, this could solve the issue for the region, but not in general for
> redisplay--update-cursor-face-highlight which was the initial problem
> with Juri's code. Same for any other function that goes into the
> pre-redisplay-functions hook.

I asked for a test case, and this is what you gave me.

If there's another test case, please show it.

> The region example reported in this issue was only the simplest way I
> found to give you a simple reproducible snippet, but the issue is a bit
> more general.
> 
> With the cursor-face we may have a similar issue cause such hook works
> in the same way, so this condition will need to be extended and extended
> and extended on every case for every function in
> pre-redisplay-functions hook.

I need to understand the more general case in practical terms.  Then I
can think about a solution.

bug#54450: 29.0.50; redisplay--pre-redisplay-functions issue

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

On Fri, Mar 18, 2022 at 08:38:18PM +0200, Eli Zaretskii wrote:
>> Date: Fri, 18 Mar 2022 18:42:52 +0100
>> From: Ergus <spacibba@aol.com>
>> Cc: 54450@debbugs.gnu.org
>>
>> >+  if (highlight_nonselected_windows
>> >+      && !NILP (Vtransient_mark_mode)
>> >+      && !NILP (BVAR (current_buffer, mark_active)))
>> >+    bset_redisplay (current_buffer);
>> >+
>> >   /* Set TO to the interval containing the char after CHARPOS,
>> >      and TOPREV to the interval containing the char before CHARPOS.
>> >      Either one may be null.  They may be equal.  */
>>
>> Hi Eli:
>>
>> Yes, this could solve the issue for the region, but not in general for
>> redisplay--update-cursor-face-highlight which was the initial problem
>> with Juri's code. Same for any other function that goes into the
>> pre-redisplay-functions hook.
>
>I asked for a test case, and this is what you gave me.
>
>If there's another test case, please show it.
>
Hi Eli

A similar issue happens if in the test buffer you do:

M-x cursor-face-highlight-mode
(setq cursor-face-highlight-nonselected-window t)
M-: (insert "AAA"(propertize "Hello World" 'cursor-face 'highlight)"BBB")

Then try to move the cursor over the inserted text with the arrows (you
should see the highlight when cursor is over the propertized text); The
try te same and from other buffer (using with-selected-window).

In the second case you will see the cursor moving but the highlighted
not updated.

>> The region example reported in this issue was only the simplest way I
>> found to give you a simple reproducible snippet, but the issue is a bit
>> more general.
>>
>> With the cursor-face we may have a similar issue cause such hook works
>> in the same way, so this condition will need to be extended and extended
>> and extended on every case for every function in
>> pre-redisplay-functions hook.
>
>I need to understand the more general case in practical terms.  Then I
>can think about a solution.

bug#54450: 29.0.50; redisplay--pre-redisplay-functions issue

[Eli Zaretskii]

> Date: Fri, 18 Mar 2022 20:38:18 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 54450@debbugs.gnu.org
> 
> > Yes, this could solve the issue for the region, but not in general for
> > redisplay--update-cursor-face-highlight which was the initial problem
> > with Juri's code. Same for any other function that goes into the
> > pre-redisplay-functions hook.
> 
> I asked for a test case, and this is what you gave me.
> 
> If there's another test case, please show it.

But before you do, please try the alternative patch below:

diff --git a/src/xdisp.c b/src/xdisp.c
index 5cb5839..6d8d4aa 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -13211,7 +13211,8 @@ prepare_menu_bars (void)
 	      struct window *w = XWINDOW (this);
 	      if (w->redisplay
 		  || XFRAME (w->frame)->redisplay
-		  || XBUFFER (w->contents)->text->redisplay)
+		  || XBUFFER (w->contents)->text->redisplay
+		  || w->last_point != marker_position (w->pointm))
 		{
 		  windows = Fcons (this, windows);
 		}

bug#54450: 29.0.50; redisplay--pre-redisplay-functions issue

[Eli Zaretskii]

> Date: Fri, 18 Mar 2022 19:52:14 +0100
> From: Ergus <spacibba@aol.com>
> Cc: 54450@debbugs.gnu.org
> 
> A similar issue happens if in the test buffer you do:
> 
> M-x cursor-face-highlight-mode
> (setq cursor-face-highlight-nonselected-window t)
> M-: (insert "AAA"(propertize "Hello World" 'cursor-face 'highlight)"BBB")

There's no such mode in master, right?

Anyway, please try the last patch I posted and see if it solves the
problem.

bug#54450: 29.0.50; redisplay--pre-redisplay-functions issue

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

On Fri, Mar 18, 2022 at 08:54:00PM +0200, Eli Zaretskii wrote:
>> Date: Fri, 18 Mar 2022 20:38:18 +0200
>> From: Eli Zaretskii <eliz@gnu.org>
>> Cc: 54450@debbugs.gnu.org
>>
>> > Yes, this could solve the issue for the region, but not in general for
>> > redisplay--update-cursor-face-highlight which was the initial problem
>> > with Juri's code. Same for any other function that goes into the
>> > pre-redisplay-functions hook.
>>
>> I asked for a test case, and this is what you gave me.
>>
>> If there's another test case, please show it.
>
>But before you do, please try the alternative patch below:
>
>diff --git a/src/xdisp.c b/src/xdisp.c
>index 5cb5839..6d8d4aa 100644
>--- a/src/xdisp.c
>+++ b/src/xdisp.c
>@@ -13211,7 +13211,8 @@ prepare_menu_bars (void)
> 	      struct window *w = XWINDOW (this);
> 	      if (w->redisplay
> 		  || XFRAME (w->frame)->redisplay
>-		  || XBUFFER (w->contents)->text->redisplay)
>+		  || XBUFFER (w->contents)->text->redisplay
>+		  || w->last_point != marker_position (w->pointm))
> 		{
> 		  windows = Fcons (this, windows);
> 		}

Yes, now this seems to solve the issue for the two use cases described.

Thanks,
Ergus

bug#54450: 29.0.50; redisplay--pre-redisplay-functions issue

[Eli Zaretskii]

> Date: Fri, 18 Mar 2022 22:25:24 +0100
> From: Ergus <spacibba@aol.com>
> Cc: 54450@debbugs.gnu.org
> 
> On Fri, Mar 18, 2022 at 08:54:00PM +0200, Eli Zaretskii wrote:
> >> Date: Fri, 18 Mar 2022 20:38:18 +0200
> >> From: Eli Zaretskii <eliz@gnu.org>
> >> Cc: 54450@debbugs.gnu.org
> >>
> >> > Yes, this could solve the issue for the region, but not in general for
> >> > redisplay--update-cursor-face-highlight which was the initial problem
> >> > with Juri's code. Same for any other function that goes into the
> >> > pre-redisplay-functions hook.
> >>
> >> I asked for a test case, and this is what you gave me.
> >>
> >> If there's another test case, please show it.
> >
> >But before you do, please try the alternative patch below:
> >
> >diff --git a/src/xdisp.c b/src/xdisp.c
> >index 5cb5839..6d8d4aa 100644
> >--- a/src/xdisp.c
> >+++ b/src/xdisp.c
> >@@ -13211,7 +13211,8 @@ prepare_menu_bars (void)
> > 	      struct window *w = XWINDOW (this);
> > 	      if (w->redisplay
> > 		  || XFRAME (w->frame)->redisplay
> >-		  || XBUFFER (w->contents)->text->redisplay)
> >+		  || XBUFFER (w->contents)->text->redisplay
> >+		  || w->last_point != marker_position (w->pointm))
> > 		{
> > 		  windows = Fcons (this, windows);
> > 		}
> 
> Yes, now this seems to solve the issue for the two use cases described.

Thanks, I installed a slightly modified variant of this on the
emacs-28 branch.