bug#52378: 28.0.50; [PATCH] Reinstate a guard on compute_window_start()

bug#52378: 28.0.50; [PATCH] Reinstate a guard on compute_window_start()

[dick.r.chiang]

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From c0d3b2f75cd1ef0d4b45442ab073d8cd0a448a08 Mon Sep 17 00:00:00 2001
From: dickmao <dick.r.chiang@gmail.com>
Date: Wed, 8 Dec 2021 16:11:34 -0500
Subject: [PATCH] A common error

* src/xdisp.c (compute_window_start_on_continuation_line):
Align code with comment.
---
 src/xdisp.c | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/xdisp.c b/src/xdisp.c
index 0ff6286af74..0fed93106df 100644
--- a/src/xdisp.c
+++ b/src/xdisp.c
@@ -18088,7 +18088,7 @@ compute_window_start_on_continuation_line (struct window *w)
          case point will not be visible with any window start we
          compute.  */
       if (IT_CHARPOS (it) <= PT
-	  || (CHARPOS (start_pos) - IT_CHARPOS (it)
+	  && (CHARPOS (start_pos) - IT_CHARPOS (it)
 	      /* PXW: Do we need upper bounds here?  */
 	      < WINDOW_TOTAL_LINES (w) * WINDOW_TOTAL_COLS (w)))
 	{
-- 
2.26.2


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bug#52378: 28.0.50; [PATCH] Reinstate a guard on compute_window_start()

[Eli Zaretskii]

> From: dick.r.chiang@gmail.com
> Date: Wed, 08 Dec 2021 16:14:27 -0500
> 
> >From c0d3b2f75cd1ef0d4b45442ab073d8cd0a448a08 Mon Sep 17 00:00:00 2001
> From: dickmao <dick.r.chiang@gmail.com>
> Date: Wed, 8 Dec 2021 16:11:34 -0500
> Subject: [PATCH] A common error
> 
> * src/xdisp.c (compute_window_start_on_continuation_line):
> Align code with comment.

The current code is correct.  It's the comment that might confuse: it
describes the conditions under which we do NOT want to execute the
code in the following block (that's what "give up" means in this
case).  So "||" is correct, and you need to reverse the conditions to
understand what the comment says.  For example, it says "too far", but
the condition says "less than", not "greater than".

I tried to clarify the comment on the release branch.

bug#52378: 28.0.50; [PATCH] Reinstate a guard on compute_window_start()

[dick]

> The current code is correct.

I don't mind the DeMorgan's errors of this kind; I am guilty of them
too.  What I do mind is willful incompetence.

bug#52378: 28.0.50; [PATCH] Reinstate a guard on compute_window_start()

[Eli Zaretskii]

> Date: Thu, 09 Dec 2021 09:22:33 +0200
> From: Eli Zaretskii <eliz@gnu.org>
> Cc: 52378-done@debbugs.gnu.org
> 
> > From: dick.r.chiang@gmail.com
> > Date: Wed, 08 Dec 2021 16:14:27 -0500
> > 
> > >From c0d3b2f75cd1ef0d4b45442ab073d8cd0a448a08 Mon Sep 17 00:00:00 2001
> > From: dickmao <dick.r.chiang@gmail.com>
> > Date: Wed, 8 Dec 2021 16:11:34 -0500
> > Subject: [PATCH] A common error
> > 
> > * src/xdisp.c (compute_window_start_on_continuation_line):
> > Align code with comment.
> 
> The current code is correct.  It's the comment that might confuse:

Actually, I take that back.  You were right.  I installed the change.