Subject: Re: bug#56815: 29.0.50; Isearch lazy-highlight highlights too much when truncate-lines is in effect

From: Juri Linkov <[email-masked]>
Date: Tue, 23 Aug 2022 19:49:40 +0300

>> >>   (or truncate-lines (truncated-partial-width-window-p))
>> >
>> > Fine by me.
>> 
>> Then I'll push a better patch:
>
> Btw, I didn't use window-total-width instead of window-width.  What I
> did mimics what the display engine does when it determines whether to
> truncate lines in a window.  So I think
> truncated-partial-width-window-p should be fixed to use
> window-total-width instead.

Now this patch fixes truncated-partial-width-window-p to use
window-total-width.  Also it fixes the recent code for
long_line_optimizations_p in scan_for_column to better mimic
what the display engine does:

diff --git a/lisp/simple.el b/lisp/simple.el
index 460aff8bd8..6e8cd798e0 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -7700,13 +7700,7 @@ line-move
                  ;; Lines are not truncated...
                  (not
                   (and
-                   (or truncate-lines
-                       (and (integerp truncate-partial-width-windows)
-                            (< (window-total-width)
-                               truncate-partial-width-windows))
-                       (and truncate-partial-width-windows
-                            (not (integerp truncate-partial-width-windows))
-                            (not (window-full-width-p))))
+                   (or truncate-lines (truncated-partial-width-window-p))
                    ;; ...or if lines are truncated, this buffer
                    ;; doesn't have very long lines.
                    (long-line-optimizations-p)))
@@ -7716,14 +7710,7 @@ line-move
 	       ;; Display-based column are incompatible with goal-column.
 	       (not goal-column)
                ;; Lines aren't truncated.
-               (not
-                (or truncate-lines
-                    (and (integerp truncate-partial-width-windows)
-                         (< (window-width)
-                            truncate-partial-width-windows))
-                    (and truncate-partial-width-windows
-                         (not (integerp truncate-partial-width-windows))
-                         (not (window-full-width-p)))))
+               (not (or truncate-lines (truncated-partial-width-window-p)))
 	       ;; When the text in the window is scrolled to the left,
 	       ;; display-based motion doesn't make sense (because each
 	       ;; logical line occupies exactly one screen line).
@@ -7983,7 +7970,7 @@ line-move-finish
 
 	;; Move to the desired column.
         (if (and line-move-visual
-                 (not (or truncate-lines truncate-partial-width-windows)))
+                 (not (or truncate-lines (truncated-partial-width-window-p))))
             ;; Under line-move-visual, goal-column should be
             ;; interpreted in units of the frame's canonical character
             ;; width, which is exactly what vertical-motion does.
diff --git a/lisp/window.el b/lisp/window.el
index 4d88ffa903..a2559a2591 100644
--- a/lisp/window.el
+++ b/lisp/window.el
@@ -9044,10 +9055,7 @@ count-screen-lines
       ;; vertical-motion returns a number that is 1 larger than it
       ;; should.  We need to fix that.
       (setq end-invisible-p
-            (and (or truncate-lines
-                     (and (natnump truncate-partial-width-windows)
-                          (< (window-total-width window)
-                             truncate-partial-width-windows)))
+            (and (or truncate-lines (truncated-partial-width-window-p window))
                  (save-excursion
                    (goto-char finish)
                    (> (- (current-column) (window-hscroll window))
@@ -10140,7 +10148,7 @@ scroll-command--goto-goal-column
   (when goal-column
     ;; Move to the desired column.
     (if (and line-move-visual
-             (not (or truncate-lines truncate-partial-width-windows)))
+             (not (or truncate-lines (truncated-partial-width-window-p))))
         ;; Under line-move-visual, goal-column should be
         ;; interpreted in units of the frame's canonical character
         ;; width, which is exactly what vertical-motion does.
@@ -10449,7 +10457,7 @@ truncated-partial-width-window-p
     (let ((t-p-w-w (buffer-local-value 'truncate-partial-width-windows
 				       (window-buffer window))))
       (if (integerp t-p-w-w)
-	  (< (window-width window) t-p-w-w)
+	  (< (window-total-width window) t-p-w-w)
         t-p-w-w))))
 
 
diff --git a/src/indent.c b/src/indent.c
index cb368024d9..aa905f387b 100644
--- a/src/indent.c
+++ b/src/indent.c
@@ -577,12 +577,15 @@ scan_for_column (ptrdiff_t *endpos, EMACS_INT *goalcol,
 
       if (!NILP (BVAR (current_buffer, truncate_lines)))
 	lines_truncated = true;
-      else if (w && FIXNUMP (Vtruncate_partial_width_windows))
-	lines_truncated =
-	  w->total_cols < XFIXNAT (Vtruncate_partial_width_windows);
-      else if (w && !NILP (Vtruncate_partial_width_windows))
-	lines_truncated =
-	  w->total_cols < FRAME_COLS (XFRAME (WINDOW_FRAME (w)));
+      else if (!NILP (Vtruncate_partial_width_windows) && w
+	       && w->total_cols < FRAME_COLS (XFRAME (WINDOW_FRAME (w))))
+	{
+	  if (FIXNUMP (Vtruncate_partial_width_windows))
+	    lines_truncated =
+	      w->total_cols < XFIXNAT (Vtruncate_partial_width_windows);
+	  else
+	    lines_truncated = true;
+	}
       /* Special optimization for buffers with long and truncated
 	 lines: assumes that each character is a single column.  */
       if (lines_truncated)