patch 9.1.1885: Wrong restored cursor pos when re-entering buffer after changes

Problem:  Wrong restored cursor position when re-entering a buffer
          previously viewed in a window after making changes to the same
          buffer in another window.
Solution: Adjust per-window "last cursor" positions on buffer changes.
          (zeertzjq)

closes: #18655

Signed-off-by: zeertzjq <zeertzjq@outlook.com>
Signed-off-by: Christian Brabandt <cb@256bit.org>

src/mark.c

@@ -1031,6 +1031,25 @@ ex_changes(exarg_T *eap UNUSED)
 	    *lp += amount_after; \
     }
 
+// Like one_adjust_nodel(), but if the position is within the deleted range,
+// move it to the start of the line before the range.
+#define one_adjust_cursor(pp) \
+    { \
+	pos_T *posp = pp; \
+	if (posp->lnum >= line1 && posp->lnum <= line2) \
+	{ \
+	    if (amount == MAXLNUM) /* line with cursor is deleted */ \
+	    { \
+		posp->lnum = MAX(line1 - 1, 1); \
+		posp->col = 0; \
+	    } \
+	    else /* keep cursor on the same line */ \
+		posp->lnum += amount; \
+	} \
+	else if (amount_after && posp->lnum > line2) \
+	    posp->lnum += amount_after; \
+    }
+
 /*
  * Adjust marks between "line1" and "line2" (inclusive) to move "amount" lines.
  * Must be called before changed_*(), appended_lines() or deleted_lines().
@@ -1075,6 +1094,7 @@ mark_adjust_internal(
     linenr_T	*lp;
     win_T	*win;
     tabpage_T	*tab;
+    wininfo_T	*wip;
     static pos_T initpos = {1, 0, 0};
 
     if (line2 < line1 && amount_after == 0L)	    // nothing to do
@@ -1192,21 +1212,7 @@ mark_adjust_internal(
 		    win->w_topfill = 0;
 #endif
 		}
-		if (win->w_cursor.lnum >= line1 && win->w_cursor.lnum <= line2)
-		{
-		    if (amount == MAXLNUM) // line with cursor is deleted
-		    {
-			if (line1 <= 1)
-			    win->w_cursor.lnum = 1;
-			else
-			    win->w_cursor.lnum = line1 - 1;
-			win->w_cursor.col = 0;
-		    }
-		    else		// keep cursor on the same line
-			win->w_cursor.lnum += amount;
-		}
-		else if (amount_after && win->w_cursor.lnum > line2)
-		    win->w_cursor.lnum += amount_after;
+		one_adjust_cursor(&(win->w_cursor));
 	    }
 
 #ifdef FEAT_FOLDING
@@ -1221,6 +1227,10 @@ mark_adjust_internal(
     // adjust diffs
     diff_mark_adjust(line1, line2, amount, amount_after);
 #endif
+
+    // adjust per-window "last cursor" positions
+    FOR_ALL_BUF_WININFO(curbuf, wip)
+	one_adjust_cursor(&(wip->wi_fpos));
 }
 
 // This code is used often, needs to be fast.

src/testdir/test_buffer.vim

@@ -623,17 +623,48 @@ func Test_switch_to_previously_viewed_buffer()
   vsplit
 
   call cursor(100, 3)
+  call assert_equal('100', getline('.'))
   edit Xotherbuf
   buffer Xviewbuf
   call assert_equal([0, 100, 3, 0], getpos('.'))
+  call assert_equal('100', getline('.'))
 
+  edit Xotherbuf
+  wincmd p
+  normal! gg10dd
+  wincmd p
+  buffer Xviewbuf
+  call assert_equal([0, 90, 3, 0], getpos('.'))
+  call assert_equal('100', getline('.'))
+
+  edit Xotherbuf
+  wincmd p
+  normal! ggP
+  wincmd p
+  buffer Xviewbuf
+  call assert_equal([0, 100, 3, 0], getpos('.'))
+  call assert_equal('100', getline('.'))
+
+  edit Xotherbuf
+  wincmd p
+  normal! 96gg10ddgg
+  wincmd p
+  buffer Xviewbuf
+  " The original cursor line was deleted, so cursor is restored to the start
+  " of the line before the deleted range.
+  call assert_equal([0, 95, 1, 0], getpos('.'))
+  call assert_equal('95', getline('.'))
+
+  normal! u
   exe win_id2win(oldwin) .. 'close'
   setlocal bufhidden=hide
 
   call cursor(200, 3)
+  call assert_equal('200', getline('.'))
   edit Xotherbuf
   buffer Xviewbuf
   call assert_equal([0, 200, 3, 0], getpos('.'))
+  call assert_equal('200', getline('.'))
 
   bwipe! Xotherbuf
   bwipe! Xviewbuf

src/version.c

@@ -729,6 +729,8 @@ static char *(features[]) =
 
 static int included_patches[] =
 {   /* Add new patch number below this line */
+/**/
+    1885,
 /**/
     1884,
 /**/